Yuba River Development Project FERC Project No. 2246

Transcription

1 TECHNICAL MEMORANDUM 2-2 Water Balance/ Operations Model November , Yuba County Water Agency All Rights Reserved

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3 TECHNICAL MEMORANDUM 2-2 EXECUTIVE SUMMARY In 2011 and 2012, the Yuba County Water Agency (YCWA) developed a water balance/operations model to simulate operations of YCWA s (Project). The Water Balance/Operations Model (model) is intended to be used to simulate current and future operations of the Project using historical hydrology to define a representative range of hydrological conditions. The model simulates Project operations on a daily timestep for a user-designated period of record. Using historic hydrology, the model simulates user-defined operations using a consistent set of operational and physical constraints to determine the Project s response to a wide range of hydrology. The model platform is Microsoft Excel, with almost all of the logic and computations written in Microsoft Visual Basic for Applications. The model uses the United States Army Corps of Engineers (USACE) Hydrologic Engineering Center Data Storage System (HEC-DSS) as a platform for input and output timeseries storage and management. The model has the capability of simulating time periods from as long as 41 years of hydrology (i.e., Water Years ( WY) 1970 through 2010) to as short a time interval as a single day. The model s lower geographic boundary is the Yuba River confluence with the Feather River. The model s upper geographic boundaries are the normal maximum water surface elevation (NMWSE) of New Bullards Bar Reservoir on the North Yuba River, the NMWSE of Log Cabin Diversion Dam on Oregon Creek, and the NMWSE of Our House Diversion Dam on the Middle Yuba River. Modeled Project facilities include the New Bullards Bar Dam and Reservoir, Log Cabin and Our House diversion dams, New Colgate Powerhouse, and Narrows 2 Powerhouse. In addition, the modeled facilities include the following non-project facilities and features: USACE s Englebright Dam and Reservoir; Pacific Gas and Electric Company s Narrows 1 Powerhouse; and agricultural diversions from the Yuba River near USACE s Daguerre Point Dam. Input hydrology to the model is a combination of historic gaged flows and synthesized hydrology. The model output includes flows on the North Yuba River, Middle Yuba River, Oregon Creek, and Yuba River below Project facilities. It also includes reservoir storage and elevation for New Bullards Bar and Englebright reservoirs; generation from the New Colgate, Narrows 1, and Narrows 2 powerhouses; and agricultural deliveries to YCWA s member units. Since the model simulates historic hydrology with physical and regulatory conditions that did not exist throughout the Project history, a direct long-term comparison of model output against historic conditions would not be practical. Therefore, a Validation Scenario was developed using historic regulatory conditions to test the model s performance in simulating historic conditions. Validation of the model was conducted in two stages: 1) a detailed evaluation was conducted for years representing the current operational regime, WYs 2008 through 2010, where each deviation from historical flows was evaluated and characterized. If needed, modifications November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page ES-1

4 were made to either the input data set or the model logic to improve the model s representation of historical operations; and 2) a broader evaluation assessing the model s performance for a period encompassing a range of operational regimes including the State Water Resource Control Board s (SWRCB) Revised Decision 1644 (RD-1644) and the Yuba River Accord (Yuba Accord). For the latter evaluation, covering WYs 2001 through 2010, many unique and changing circumstances have occurred which affected flow and storage conditions. These include individual decisions that were made in managing storage and anticipated snowmelt runoff, or that were no longer used operational practices. It is not the intent of the WY 2001 to WY 2010 validation series to capture all, or even most of these occurrences, but rather to demonstrate that the model results provide a reasonable approximation of the hydrologic conditions even without incorporating these unique operations into the model. Individual deviations from historical operations were not as closely scrutinized for the WY 2001 to WY 2010 validation series, but the general model logic was evaluated against historical operations to ensure there were no long-term effects that resulted in significant deviations from historical conditions over multiple years, due to faulty model logic. Again, if needed, modifications were made to either the input dataset or the mode logic to improve the model s representation of historical operations. The model meets the intended purpose of supporting the relicensing process by reasonably simulating the hydrology of the Yuba River watershed and providing an accurate simulation of the Project facilities and operations. After validating the model, YCWA developed a Base Case Scenario. 1 The Base Case Scenario includes a representation of the regulatory requirements affecting Project operations. The Base Case Scenario also includes a representation of current agricultural irrigation demands served by the Project, and hydrology that results from the current operations of facilities owned and operated by others upstream from the Project. Lastly, the Base Case Scenario includes a representation of Project operational practices such as New Bullards Bar Reservoir Target Operating Line operations, New Bullards Bar Reservoir carryover storage operations, New Colgate Powerhouse operations, and Englebright Reservoir operations all of which are current operating practices in the watershed. Throughout the model development process, YCWA met with Relicensing Participants to ensure they were informed on the progress of the model development and model workings. YCWA issued a draft of the Model, a Validation Report, and a Model Development Report and held meetings to receive comments. The Model Development Report, the Model Validation Report, the Base Case Report, the Hydrology Report, and the Model configured in the Base Case are attached to this technical memorandum. 1 The Base Case represents conditions as they currently exist, with the current rules, regulations, water supply demands, and operational practices. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page ES , Yuba County Water Agency

5 This study was conducted according to Study 2.2, Water Balance/Operations Model, with five variances. First, the FERC-approved study indicated the model would include both inflows from Dry Creek near its confluence with the Yuba River, and from ungaged tributaries to the Yuba River below Englebright Dam. Accretions from these two locations were consolidated into a single accretion in the model because no consistent, predictable trend for predicting non-dry Creek accretions to the Yuba River below Englebright Dam could be identified. Second, the FERC-approved study indicated a Microsoft Excel spreadsheet for post-processing daily model output into hourly or 15-minute patterns would be developed. This post-processor was not developed because it was determined through the consultation process that there was no need for a sub-daily timestep. Third, the FERC-approved study indicated the model would include three options for splitting Englebright Reservoir releases between the Narrows 1 and Narrows 2 powerhouses. The model includes two options, a Narrows 1 Powerhouse preference, and a Narrows 2 Powerhouse preference because YCWA considered the third option, a post-relicensing split, too speculative prior to negotiations with PG&E regarding potential post-relicensing generation scenarios. Fourth, the FERC-approved study indicated the model would provide output representing both the North and South Canal diversions, but the model aggregates all agricultural diversions into a single diversion point because it was decided by YCWA that individual irrigation deliveries are outside of the scope of the relicensing process. Last, The FERC-approved study specified the study be completed by the end of September The quality assurance/quality control review of study results took longer than anticipated resulting in a slight delay of study completion. The five variances identified did not affect the study or overall relicensing schedule. The study is complete. 2 2 While the study is complete, if errors or needed modifications to the model are identified during the relicensing, YCWA is committed to making the changes to the model at that time and distributing a revised model. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page ES-3

6 Page Left Blank Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page ES , Yuba County Water Agency

7 Table of Contents Section No. Description Page No. Executive Summary...ES Goals and Objectives Methods Study Area Model Development Input Hydrology to Model Facilities Included in Model Operations Considerations Model Output Model Validation Base Case Development Model Documentation Results Model Development Model Validation End-of-Day New Bullards Bar Reservoir Storage Daily Average Releases from New Colgate Powerhouse Daily Average Middle Yuba River Flow Below Our House Diversion Dam Daily Average Yuba River Flow at Smartsville Daily Average Yuba River Flow at Marysville Base Case Scenario Model Documentation Discussion Model Development Model Validation Study-Specific Consultation Consult Regarding Model Development Variances from FERC-Approved Study Attachments to this Technical Memorandum References...30 November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page TOC-i

8 List of Figures Figure No. Description Page No Study area for Study 2.2, Water Balance/Operations Model Storage in New Bullards Bar Reservoir Storage in New Bullards Bar Reservoir for Water Year 2001 through Mean Daily New Colgate Powerhouse Release (USGS gage ) with 7 day moving average of historical releases Mean Daily Flow at Below Our House Dam (USGS gage ) Mean Daily Flows below Englebright Dam (USGS gage ) Mean Daily Flow at Marysville Gage (USGS gage ) List of Tables Table No. Description Page No Relicensing Participant meetings for consultation on Operations/Water Balance Model development List of Attachments Attachment 2-2A Attachment 2-2B Attachment 2-2C Attachment 2-2D Attachment 2-2E Attachment 2-2F Model Development Report Model Validation Report Base Case Report Hydrology Report Water Balance/Operations Model Configured in the Base Case Scenario and in the Validation Scenario Dated November 2012 Hydrology Data Sets Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page TOC-ii 2012, Yuba County Water Agency

9 TECHNICAL MEMORANDUM 2-2 WATER BALANCE/OPERATIONS MODEL 3 Yuba County Water Agency Yuba County Water Agency s (YCWA) continued operation and maintenance (O&M) of the, Federal Energy Regulatory Commission (FERC or Commission) Project Number 2246 (Project) will affect hydrology in stream reaches downstream of the Project. 1.0 Goals and Objectives The goal of the study was to develop a water balance/operations model to simulate current and future operations of the Project using historical hydrology to define a representative range of hydrological conditions, and to output resulting flows, reservoir storage and water surface elevations and power generation for use by the YCWA and Relicensing Participants in the relicensing. 4 The objectives of the study were to develop the model in a fashion that results in all interested Relicensing Participants agreeing the model is reasonably reliable for the purposes of relicensing, and agreeing to use this single water balance/operations model to make relicensing recommendations. Primary objectives included developing a model that simulates Project O&M for a period of analysis that covers a range of hydrologic conditions. The model should: Address operational decisions made during Project O&M including: flood control; water supply; recreation; stream flows for fisheries and other aquatic resources; and hydropower generation. Accurately reproduce observed reservoir levels, reservoir releases, and hydropower generation, within acceptable calibration standards over a range of hydrologic conditions. Provide output to inform other studies, analyses, and models. Allow simulation of changes in Project O&M to determine effects on reservoir levels, reservoir releases, stream flows and hydropower generation. 2.0 Methods The study was conducted in five steps, each of which is described below. 3 4 This technical memorandum presents the results for Study 2.2, Water Balance/Operations Model, which was included in YCWA s August 17, 2011 Revised Study Plan for relicensing of the, and approved by FERC in its September 30, 2011 Study Plan Determination. There were no modifications to Study 2.2 subsequent to FERC s September 30, 2011 Study Determination. Model runs beyond those specifically identified in the FERC-approved study were not part of the study. However, after the study is complete, YCWA is willing to make a reasonable number of model runs as collaboratively agreed to between YCWA and Relicensing Participants. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 1 of 32

10 2.1 Study Area The study area included: 1) the Middle Yuba River from and including Our House Diversion Dam Impoundment to the confluence with the North Yuba River; 2) Oregon Creek from and including the Log Cabin Diversion Dam Impoundment to the confluence with the Middle Yuba River; 3) the North Yuba River from and including New Bullards Bar Dam Reservoir to the confluence with the Middle Yuba River; and 4) and the portion of the Yuba River from the confluence of the North and Middle Yuba rivers to the Feather River. Figure shows the extent of the study area. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 2 of , Yuba County Water Agency

11 Figure Study area for Study 2.2, Water Balance/Operations Model. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 3 of 32

12 2.2 Model Development The Water Balance/Operations Model (model) was developed between December 2008 and June Model development occurred in multiple phases, including development of input hydrology, development of the representation of Project facilities, and development of operational rules. The model simulates Project operations on a daily timestep for a user-designated period of record. Using historic hydrology, the model simulates user-defined operations using a consistent set of operational and physical constraints to determine the Project s response to a wide range of hydrology. The model platform is Microsoft Excel, with almost all of the logic and computations written in Microsoft Visual Basic for Applications. The model uses the United States Army Corps of Engineers (USACE) Hydrologic Engineering Center Data Storage System (HEC-DSS) as a platform for input and output timeseries storage and management. The model has the capability of simulating time periods from as long as 41 years of hydrology (i.e., water years (WY) 1970 through 2010) to as short a time interval as a single day Input Hydrology to Model The model simulated Project operations for a 41-year hydrology period of record from Water Year (WY) 1970 through WY Input hydrology representing this period was developed for the following locations using a combination of historical gage data and synthetic accretions: Historical data from United States Geological Survey (USGS) gages were used for the following locations: North Yuba River above Goodyears Bar Slate Creek below South Feather Water and Power Agency s South Feather Power Project s Slate Creek Diversion Dam Oregon Creek above Log Cabin Diversion Dam Middle Yuba River above Our House Dam South Yuba River above Jones Bar Deer Creek below Nevada Irrigation District s Lake Wildwood Dam Dry Creek near its confluence with the Yuba River Synthesized historical accretions were developed using regressions relating watershed area, average annual precipitation, and hydrologic characteristics to historical gaged data from gages representing unimpaired watersheds. Synthesized historical accretions were developed for the following locations: Canyon Creek inflow to the North Yuba River Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 4 of , Yuba County Water Agency

13 Accretions to Slate Creek below South Feather Water and Power Agency s South Feather Power Project s Slate Creek Diversion Dam Accretions to the North Yuba River between Goodyears Bar and New Bullards Bar Reservoir Accretions to the North Yuba River between Slate Creek and New Bullards Bar Dam Accretions to Oregon Creek below the Log Cabin Diversion Dam Accretions to the Middle Yuba River between Our House Dam and the Middle Yuba River s confluence with Oregon Creek Accretions to the Middle Yuba River between its confluence with Oregon Creek and its confluence with the North Yuba River Accretions to the North Yuba and Yuba rivers between New Bullards Bar Dam and Colgate Powerhouse Accretions to the Yuba River between the Colgate Powerhouse and Englebright Dam Accretions to the South Yuba River below Jones Bar Dry Creek inflow to the Yuba River For the purpose of relicensing, YCWA has compiled three hydrology datasets used for the evaluations in this study and for use in other relicensing studies: 1) Historical Hydrology; Without-Project Hydrology; and With-Project Hydrology. The description of each is provided below. Historical Hydrology (i.e., gaged flows). The Historical Hydrology is the measured (i.e., gaged) mean daily hydrology. This data set is primarily composed of the measured hydrology from start of the project in WY 1970 through WY 2010 for the geographic area from just upstream of the Project to the USGS Marysville streamflow gage, which is located on the Yuba River upstream of the Feather River. In addition, this data set includes data from as early as 1900 for several gages. The Historical Hydrology data set for locations downstream of Project facilities is representative of Project operations throughout its history. 5 The Historical Hydrology does not require a model run. Without-Project Hydrology. The Without-Project Hydrology is the mean daily hydrology as if the Project had not been constructed (i.e., no Project facilities in place), but all other water projects in the basin are operating. This data set is comprised of measured hydrology and synthesized hydrology from WY 1970 through WY 2010 for the geographic area from just upstream of all YRDP facilities to the USGS Marysville gage, which is just upstream of where backwater effects of the Feather River become apparent. 5 A significant shift in the Historical Hydrology occurred in From WY 1970 through WY 2005 the Project was operated under either the existing FERC license minimum flow requirements or the California State Water Resource Control Board (SWRCB) Revised Decision 1644 (RD-1644). Beginning in WY 2006, the Project was operated under the Yuba River Accord flow requirements, which are higher than the flow requirements in the existing FERC license. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 5 of 32

14 The Without-Project Hydrology for areas upstream from the Project is the measured hydrology from the Historical Hydrology data set (i.e., inflow to the Project). The Without-Project Hydrology downstream of Project facilities is synthesized hydrology that consists of calculated accretions downstream from the inflow measurement locations plus the relevant measured inflows (i.e., in the Project area and downstream). 6 The Without- Project Hydrology does not require a model run. With-Project Hydrology. The With-Project Hydrology is current conditions (i.e., with the Project in operation and with the existing flow requirements and operational practices). This data set is comprised of mean daily hydrology for the geographic area from just upstream of the Project to the USGS Marysville gage for WY 1970 through WY The measured inflows and synthesized accretions used in the Without-Project Hydrology are used as inputs to YCWA s relicensing Water Balance/Operations Model. The With-Project Hydrology dataset is produced from a model run, and can also be called the Base Case. 7 Each of the three data sets is provided in Attachment 2-2F. A complete description of the Project inflow hydrology and its development is provided in Attachment 2-2D Facilities Included in Model Project facilities included in the model include the following: Our House Diversion Dam Lohman Ridge Diversion Tunnel Log Cabin Diversion Dam Camptonville Diversion Tunnel New Bullards Bar Dam and Reservoir New Colgate Power Tunnel and Penstock New Colgate Powerhouse Narrows 2 Power Tunnel Narrows 2 Powerhouse The New Bullards Bar Dam Minimum Flow Powerhouse 6 7 YCWA has not evaluated a Yuba basin unimpaired flow data set for the relicensing because it would have no meaning for the relicensing. Other water projects, including South Feather Water and Power Agency s South Feather Power Project (FERC Project No. 2088), Nevada Irrigation District s Yuba-Bear Hydroelectric Project (FERC Project No. 2266) and Pacific Gas and Electric Company s Drum-Spaulding Project (FERC Project No. 2310) substantially affect flows into YCWA s. These upstream Projects are in various stages of relicensing. YCWA used the upstream historic regulated flows in the model. See Section 4.3 for a detailed description of Base Case assumptions. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 6 of , Yuba County Water Agency

15 Non-Project facilities included in the model include the following: USACE s Englebright Dam and Reservoir Pacific Gas & Electric Company s (PG&E) Narrows 1 Powerhouse USACE s Daguerre Point Dam Agricultural diversions on the Yuba River downstream of Englebright Dam Operations Considerations New Bullards Bar Reservoir s representation was developed to include the following operational considerations: Basic flood management operations at New Bullards Bar Reservoir Basic flood management operations at Englebright Reservoir Seasonal reservoir storage management at New Bullards Bar Reservoir Weekly and daily storage management at Englebright Reservoir Oregon Creek, Middle Yuba River, North Yuba River, and Yuba River instream flow requirements Agricultural diversions to YCWA s contractors and Yuba River water rights holders at Daguerre Point Dam Power generation at the New Colgate Powerhouse Power generation at the Narrows 2 Powerhouse Power Generation at PG&E s Narrows 1 Powerhouse Releases from the NBB minimum flow powerhouse Historical generation, flow, and head from YCWA-provided data were used to develop new efficiency curves for both the Narrows 2 and New Colgate powerhouses. Simulated flow and head were used with the computed efficiency curves to calculate generation resulting from Project operations at the New Colgate and Narrows 2 powerhouses. Similar information previously provided by PG&E was used to develop curves to calculate generation at the Narrows 1 Powerhouse. Several additional critical Project operations were included in the model. Those operations are described below. 8 Other than some minor, ungaged riparian diversions, all agricultural diversions on the Yuba River occur near Daguerre Point Dam. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 7 of 32

16 Yuba River Accord Index and Schedule Determination The currently-controlling flow requirements on the Yuba River below Englebright Dam are defined by the Lower Yuba River Accord (Accord) (YCWA 2007). The Accord flow requirements are determined based on the North Yuba Index (NYI), which is computed by adding the previous water year s end-of-september storage to the current year s inflow to New Bullards Bar Reservoir. Since the end-of-september storage is a product of the current year s operations, the NYI can be affected by changes in operations, and must be computed each year. The model calculates the NYI each year by using the previous year s end-of-september New Bullards Bar Reservoir storage, and assumes perfect foresight for inflows to New Bullards Bar Reservoir, including inflow from the Camptonville Tunnel. After calculating the NYI, the model identifies the appropriate flow requirements for the Smartsville and Marysville gages, and includes them in Project operations simulation. The NYI should not be confused with the Yuba River Index, which was developed by YCWA to support the California State Water Resource Control Board (SWRCB) Revised Decision 1644 (RD-1644) (SWRCB 2000). Carryover Storage in New Bullards Bar Reservoir New Bullards Bar Reservoir carryover storage is the volume of storage necessary at the end of September to ensure that minimum instream flow requirements and a portion of modeled irrigation deliveries can be met in the subsequent year, assuming the subsequent year is extremely dry. The carryover storage requirement assumed the driest-year requirements of the controlling regulatory flow requirements will be met in the following year. This volume is dependant on the flow regime being simulated; for example, the Base Case Scenario assumes the Yuba River Accord (Yuba Accord) flow schedules are in place and the model will meet Schedule 6 flow requirements in the driest year. The model also allows the user to specify a target percentage of modeled irrigation demand in the following year, and computes the volume required to meet those deliveries. The Base Case Scenario carryover storage calculation assumes at least 50 percent of irrigation demand will be met in the subsequent year. Last, using regressions to compute New Bullards Bar Reservoir inflow from unimpaired Yuba River flow at Smartville, and then, assuming a log-normal distribution, a user specified return period annual volume is computed for inflow. The Base Case Scenario assumes a 99 percent exceedance annual inflow volume. The difference between the required volume to meet flow requirements and agricultural deliveries, and the computed inflow volume is the volume required to be held in storage at the end of September, plus the reservoir s FERC minimum pool volume of 234,000 acre-feet (ac-ft), and an assumed 15,000 ac-ft loss to evaporation. If, after simulating a year, the end-of-september storage is less than the computed carryover storage volume, the model will re-simulate the year using a reduced irrigation delivery volume. The model will continue to iterate until either the end-of-september storage meets the carryover storage volume or the reductions in current year deliveries exceed a user-specified level. In the Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 8 of , Yuba County Water Agency

17 Base Case Scenario, the maximum current-year irrigation delivery reduction is 50 percent of a given year s irrigation demand. Intra-day Peaking Operations of New Colgate Powerhouse The model can reflect some of the New Colgate Powerhouse s operations for responding to California s power market. Historically, daily average power prices on weekdays have been higher than those on weekends. The model includes the ability to skew New Colgate Powerhouse releases so that the majority of releases occur on a particular day, or days. The user can specify a percentage of total weekly release volume for each weekday to represent a pattern of generation value that changes according to day of the week. After simulating a given year, if the option to skew operations to take advantage of differences in daily generation value has been selected, the model will re-operate each week, running from Monday through Sunday, modifying New Colgate Powerhouse generation to release the specified percentage of weekly release volume each day. This operation does not result in changed releases from Englebright Dam to the Yuba River, nor does it affect releases from Log Cabin or Our House diversion dams, or from the New Bullards Bar Minimum Flow Powerhouse. The modified releases from the New Colgate Powerhouse result in changes in Englebright Reservoir storage. If the re-operation of releases from New Colgate Powerhouse would result in Englebright Reservoir storage either dropping below a minimum threshold, or exceeding a maximum threshold, releases from New Colgate Powerhouse are adjusted. In the case where spill is already occurring at New Bullards Bar Dam or Englebright Dam, no power market-based modifications to the New Colgate Powerhouse releases are allowed. No re-operation of the New Colgate Powerhouse for this inter-day peaking operation is assumed in the Base Case Scenario. Englebright Coordinated Operations Since both YCWA and PG&E operate powerhouses downstream from Englebright Dam that release to the Yuba River, the model includes logic to simulate a preference for one powerhouse or the other. While the FERC-approved study indicated three operational modes would be included, only two were actually developed in the model; a Narrows 1 preference mode, and a Narrows 2 preference mode; the FERC-approved study included developing a Post-Relicensing Mode, which was intended to represent the criteria for the split of releases from Narrows 2 and Narrows 1 powerhouses that would be used after the end of the current FERC license, when the current Power Purchase Agreement between YCWA and PG&E no longer will be in effect. Because a new set of criteria has not been developed, it was premature to assume any particular post-relicensing operation. The model maximizes the use of one powerhouse or the other, but neither of these modes affects flows in the Yuba River below Englebright Dam. For the Base Case Scenario, the Narrows 1 preference mode was used Model Output The model outputs an extensive array of time series data of flow, storage and generation. All of the outputs are either explicitly output or can be computed by combining two or more model output parameters. Table lists the standard model output. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 9 of 32

18 Table Standard Water Balance/Operations Model output. Location Parameter (units) Model Output Identification MIDDLE YUBA RIVER OUR HOUSE DIVERSION DAM REACH 1 Inflow to Our House Diversion Dam Flow (cfs) INF_MYUBA Lohman Ridge Tunnel diversion Flow (cfs) LOHMANRIDGE_TUNNEL, REACH_19 Total flow below Our House Diversion Dam Flow (cfs) OUR_HOUSE_RELEASE, REACH_17 Minimum instream flow requirement below Our House Diversion Dam Flow (cfs) OUR_HOUSE_MIF Middle Yuba River accretions between Our House Diversion Dam and Oregon Creek Flow (cfs) INF_MYUBA_ACC1 Middle Yuba River flow between Oregon Creek and the North Yuba River Flow (cfs) REACH_16 Middle Yuba River accretions between Oregon Creek and the North Yuba River Flow (cfs) INF_MYUBA_ACC2 OREGON CREEK LOG CABIN DIVERSION DAM REACH 2 Inflow to Log Cabin Diversion Dam Flow (cfs) INF_OREGONCR Camptonville Tunnel diversion Flow (cfs) CAMPTONVILLE_TUNNEL, REACH_20 Total flow below Log Cabin Diversion Dam Flow (cfs) LOG_CABIN, REACH_15 Minimum instream flow requirement below Log Cabin Diversion Dam Flow (cfs) LOG_CABIN_MIF Oregon Creek accretions between Log Cabin Diversion Dam and the Middle Yuba River Flow (cfs) INF_OREGONCR_ACC NORTH YUBA RIVER NEW BULLARDS BAR DAM REACH 3 North Yuba River flow at Goodyears Bar INF_NYUBA, Flow (cfs) Gage REACH12 North Yuba River accretions between the Goodyears Bar Gage and Canyon Creek Flow (cfs) INF_NYUBA_ACC Canyon Creek flow to the North Yuba River Flow (cfs) INF_CANYONCR_ACC Slate Creek flow below the Slate Creek INF_SLATECR, Flow (cfs) Diversion Dam REACH_21 Slate Creek accretions between the Slate Creek Diversion Dam and the North Yuba Flow (cfs) INF_SLATECR_ACC River North Yuba River accretions between Canyon Creek and New Bullards Bar Dam Flow (cfs) INF_NBB_ACC Total natural inflows to New Bullards Bar Reservoir Flow (cfs) INF_NBB_TOTAL Total inflows to New Bullards Bar Reservoir Flow (cfs) REACH_10 New Bullards Bar Reservoir storage Storage (AF) NBB_STORAGE New Bullards Bar Reservoir water surface elevation Elevation (ft) NBB_ELEVATION Total New Bullards Bar Reservoir releases Flow (cfs) NBB_RELEASE New Bullards Bar Reservoir Flood Control Reservation Storage (AF) NBB_FLOOD_POOL New Bullards Bar Reservoir evaporation Evaporation (cfs) NBB_EVAP New Bullards Bar Reservoir upper and lower NBB_UPPERTARGET_LINE, Storage (AF) target operating lines NBB_LOWERTARGET_LINE New Bullards Bar Reservoir spills Flow (cfs) NBB_SPILL New Bullards Bar Dam minimum flow powerhouse release Flow (cfs) FISH_HYDRO Total North Yuba River flow below New Bullards Bar Dam Flow (cfs) REACH_9 Minimum instream flow requirement below New Bullards Bar Dam Flow (cfs) NBB_MIF New Colgate Penstock flow Flow (cfs) COLGATE_FLOW, REACH_18 New Colgate Powerhouse generation Generation (KWh) COLGATE_GEN Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 10 of , Yuba County Water Agency

19 Table (continued) Location Parameter (units) Model Output Identification YUBA RIVER NORTH AND MIDDLE YUBA RIVER CONFLUENCE REACH 4 Yuba River flow between North Yuba and Middle Yuba rivers confluence Flow (cfs) REACH_8 North Yuba and Yuba rivers accretions between New Bullards Bar Dam and Colgate Powerhouse Flow (cfs) INF_UPPERYUBA_ACC YUBA RIVER NEW COLGATE POWERHOUSE REACH 5 Yuba River downstream from New Colgate Powerhouse Flow (cfs) REACH_7 YUBA RIVER ENGLEBRIGHT DAM REACH 6 Englebright Reservoir Storage Storage (AF) ENG_STORAGE Englebright Reservoir water surface elevation Elevation (ft) ENG_ELEVATION Englebright Reservoir Evaporation Evaporation (cfs) ENG_EVAP Englebright Reservoir total release Flow (cfs) ENG_RELEASE Englebright Reservoir spill Flow (cfs) ENG_SPILL Englebright Reservoir inflow from sources other than New Bullards Bar Reservoir Flow (cfs) ENG_INFLOW_TOTAL releases Narrows 1 Powerhouse release Flow (cfs) NARROWS1_FLOW Narrows 1 Powerhouse generation Power (KWh) NARROWS1_GEN Narrows 2 Powerhouse release Flow (cfs) NARROWS2_FLOW Narrows 2 Powerhouse generation Power (KWh) NARROWS2_GEN Narrows 2 Powerhouse bypass Flow (cfs) NARROWS2_BYPASS Total release through Narrows 1 and Narrows 2 powerhouses Flow (cfs) NARROWS_FLOW Total generation from Narrows 1 and Narrows 2 powerhouses Power (KWh) NARROWS_GEN Yuba River flow at Smartsville Flow (cfs) SMV_FLOW, REACH_5 Minimum instream flow requirement at Smartsville Deer Creek inflow to the Yuba River Flow (cfs) Flow (cfs) SMV_MIF INF_DEERCR, REACH_13 Yuba River flow between Deer Creek and Dry Creek Flow (cfs) REACH_4 Dry Creek inflow Flow (cfs) INF_DRYCR Yuba River flow between Dry Creek and Daguerre Point Dam Flow (cfs) REACH_3 YUBA RIVER DAGUERRE POINT DAM REACH 7 Irrigation Deliveries from Daguerre Point Dam Flow (cfs) DGP_DIV Irrigation Demand from Daguerre Point Dam Flow (cfs) DGP_DEM Allocation of Daguerre Point Dam Demands Allocation (%) DGP_ALLOC Yuba River flow between Daguerre Point Dam and the Marysville Gage Flow (cfs) REACH_2 Yuba River flow at the Marysville gage Flow (cfs) MRY_FLOW Minimum instream flow requirements at the Marysville gage Flow (cfs) MRY_MIF Yuba River flow between the Marysville gage and the Feather River Flow (cfs) REACH_1 1 Our House Diversion Dam Reach - Middle Yuba River from Our House Diversion Dam to immediately upstream of the confluence with the North Yuba River. 2 Log Cabin Diversion Dam Reach - Oregon Creek from Log Cabin Diversion Dam to immediately upstream of the confluence with the Middle Yuba River. 3 New Bullards Bar Dam Reach - North Yuba River upstream of the confluence with the Middle Yuba River 4 North and Middle Confluence Reach - Yuba River from the confluence of the North Yuba River and the Middle Yuba River to upstream of Colgate Powerhouse. 5 Colgate Powerhouse Reach - Yuba River from the Colgate Powerhouse to the normal maximum water surface elevation of Englebright Reservoir. 6 Englebright Dam Reach - Yuba River from and including Englebright Reservoir to Daguerre Point Dam. 7 Daguerre Point Diversion Dam Reach - Yuba River from the Daguerre Point Dam to the Feather River. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 11 of 32

20 A complete description of the model is provided in Attachment 2-2A. 2.3 Model Validation Since the model simulates historical hydrology against physical and regulatory conditions that did not exist throughout the Project history, a direct long-term comparison of model output against historical conditions would not be practical. A validation scenario was developed using historical regulatory conditions to test the model s performance in simulating historical conditions, but other than for the validation scenario, the model output should not be compared to historical conditions. The validation scenario is documented in Attachment 2-2B. The process of finalizing a mathematical model after it has been coded includes three steps: verification; calibration; and validation. These steps occur in parallel with model development and they usually result in corrections and modifications to the model. Verification is the process of checking lines of code to ensure that calculations and data manipulation are done correctly. An example of model verification would be checking that a formula is used correctly, that program code implements the formula correctly, and that operations in which results are passed to the next model step or stored are done correctly. Calibration is the process of adjusting variable parameters so that known results are produced when modeling a known set of inputs. Validation means that a model is acceptable for its intended use because it meets specified performance requirements (Rykiel, 1995). The validation process for the model includes comparing model results of streamflow, reservoir storage and power generation with historical data, when historical conditions are modeled. For the model, verification and calibration work were a continuous process throughout the Model development to complete code sections. The validation process for the model included running a model simulation that used historical hydrology and conditions to obtain streamflow, diversions, reservoir storage and power generation and then comparing those results both quantitatively and qualitatively with historical data. The intent of validation was to demonstrate that the model provides reasonably accurate results for simulation of watershed hydrology and Project facility operations. Statistical summary tables are provided for key results. A static accuracy level to determine pass or fail of the validation was not used. Instead, the review of validation results for each output included a general discussion of the relative significance of variation or agreement with historical data. This was done because one-size-does-not-fit-all for validation. As an example, a 10 percent variation on a flow at a key location that is 2,000 cfs and therefore has a variation of 200 cfs could be a significant deviation from historical data, whereas a 10 percent variation from historical data at a location that has a flow of 30 cfs and thus a 3 cfs variation may not have any significance to establishing model accuracy, as long as these small variations would not violate minimum instream flow requirements. This is assured in the model because minimum instream flows are handled as hard constraints with added buffers. Validation of the model was conducted for two series of water years. WYs 2008 through 2010 represents the current operational regime that includes the Yuba Accord, which was implemented as a long term program in 2008, and separate validation of the model s continuous simulation capacity was conducted for the 10-year period of WYs 2001 to The selection Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 12 of , Yuba County Water Agency

21 of years for the 3-year simulation was because these years represent a range of hydrology and most closely represent current operations, including the streamflow requirements of the Yuba Accord. The intent of including the simulation of a longer series of years was to demonstrate the model s ability to represent a wide range of year-to-year hydrology, showing that the model does not diverge from historical flow and storage amounts, but re-converges to subsequent year historical conditions, even under individual year variance. Through the WY 2001 to WY 2010 historical period, many unique and changing circumstances have occurred which affected flow and storage conditions. These include individual decisions that were made in managing storage and anticipated snowmelt runoff, or that were no longer used operational practices. It is not the intent of the WY 2001 to WY 2010 validation series to capture all, or even most of these occurrences, but rather to demonstrate that the model results provide a reasonable approximation of the hydrologic conditions even without incorporating these unique operations into the model. The 3-year validation simulation of WYs 2008 through 2010 closely approximates the historical conditions for flows below Project facilities, reservoir storage in New Bullards Bar Reservoir and power generation at both powerhouses. No attempt was made to accurately simulate the historical storage in Englebright Reservoir except for operations during storms where spills are occurring at Englebright Dam. Annual unimpaired flow volumes of the Yuba River at Smartsville for the 3 years of validation are 50 percent, 72 percent and 77 percent of the 50-year average unimpaired runoff volume (WYs 1961 through 2010). Although the annual unimpaired volumes for WYs 2009 and 2010 are relatively close, the snowpack and resulting spring and early summer runoff of WY 2010 were much greater than in WY While the April through July 2009 unimpaired runoff of the Yuba River at Smartsville was 84 percent of average, the April to July 2010 unimpaired runoff was 120 percent of average or about 50 percent greater in 2010 than Conversely, the late fall and winter 2009 unimpaired runoff was almost 50 percent greater than the runoff for the same period of Therefore these two years provide hydrology that included a wet winter and dry spring (2009) and a dry winter and wet spring (2010) for validating the model. For simulation of the WY 2008 through WY 2010 period and the WY 2001 through 2010 period, a time series of daily values for several parameters were used in place of model generated daily values. For the validation simulations, the model is forced to use time series daily values for the Marysville Gage Required Flow and the Smartsville Gage Required Flow rather than internally calculate them. The model also used time series data for three additional parameters: historical agricultural diversions; the New Bullards Bar Reservoir lower target storage; and the New Bullards Bar Reservoir upper target storage. The list of time series data that are specific to the validation process are the following: Marysville Gage Required Flow Smartville Gage Required Flow Daguerre Diversions November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 13 of 32

22 New Bullards Bar Reservoir Lower Target Line New Bullards Bar Reservoir Upper Target Line Without these timeseries, the model would look up the Marysville Gage and Smartville Gage required instream flows, computing the flow requirements based on the model computation process rather than the actual historical requirements. Without the use of complete simulation period daily time series values for diversions and the upper and lower target lines, the model would use the wet and dry WY synthetic diversion data from the standard input file, which was used in the Base Case Scenario, and would look up the target line values from the table on the Inputs-Timeseries tab. Historically, for the period of WYs 2001 through 2007, operations were not always governed by only the required instream flows. In all dry WYs prior to 2008, additional water was released in the summer for stored water transfers and, for most dry WYs, an additional amount of water was released as part of groundwater substitution transfers. At other times, additional releases were made to benefit fish during the fall spawning period. Use of a full simulation period time series for required flows allows for the simulation of these unique historical flows. In addition to these requirements, when simulating the 10-year period of WYs 2001 through 2010, the instream flow requirements changed. In 2008, the Yuba Accord went into effect on a permanent basis. Prior to 2008, the SWRCB RD-1644 flow requirements were in place. The model does not have the capability to change instream flow requirements during a simulation. For diversions, the present-day diversion level has only been in place since 2010, when the Wheatland Canal began operation. Therefore, to properly represent historical diversions, a time series is used. Finally, because of these two historical differences (i.e., instream flows and diversions), a single annual time series of reservoir storage targets would not properly represent changes to the management of storage in New Bullards Bar Reservoir under differing downstream controlling demands for diversion and instream flows, and therefore a historical, annually varying series is used. Output from the 3-year validation process was provided at several key locations as follows: End-of-day New Bullards Bar Reservoir storage Daily average releases from the New Colgate Powerhouse Daily average Middle Yuba River flow below Our House Dam Daily average Yuba River flow at Smartsville Daily average Yuba River flow at Marysville Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 14 of , Yuba County Water Agency

23 Substantial variations between historical conditions and simulated conditions were examined, and where appropriate, adjustments to the model were made to correct for the variations, or the variations were explained. Output from the longer-period validation process was provided for end-of-day New Bullards Bar Reservoir storage to ensure there were no long-term deviations from historical operations A complete description of the model validation is provided in Attachment 2-2B. 2.4 Base Case Development The Project is subject to a wide range of regulatory requirements and agreements, diversion demands, and operational practices. The Base Case was developed to represent current Project operations according to existing requirements, agreements, and practices. It also includes initial conditions and the previously-mentioned representation of historical Project hydrology. It is intended that the Base Case scenario represents the No-Action Alternative and will serve as the basis of comparison for future action alternatives. A complete description of the model Base Case is provided in Attachment 2-2C. 2.5 Model Documentation As the Model was in the process of being developed, a Model Development Report was written, describing the assumptions, Model operation, and the process of Model development. The Model Development Report describes the facility capacities and other physical and regulatory constraints. A complete description of the Model is provided in Attachment 2-2A, Model Development Report. Additionally, a Hydrology Report was developed to capture the methods and assumptions associated with the development of the Model inflow hydrology. Attachment 2-2D includes the Model Hydrology Report. 3.0 Results The following section briefly describes the results of the study. Detailed results are provided in Attachments 2-2A, 2-2B, 2-2C and 2-2D. 3.1 Model Development The model has the ability to simulate the operations of New Bullards Bar Dam and Reservoir, Our House Dam, Log Cabin Dam, the Lohman Ridge Tunnel, the Camptonville Tunnel, the New Colgate Powerhouse, Englebright Dam and Reservoir, the Narrows 1 and 2 powerhouses, and agricultural deliveries to YCWA member units. The model includes the ability to operate New Bullards Bar Reservoir for basic flood management requirements, but not intra-day aspects of the November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 15 of 32

24 USACE flood control requirements (USACE 1972), agricultural irrigation deliveries, minimum flow requirements, and power generation. The model has the ability to simulate any available period of hydrologic input data, read from a HEC-DSS file. The hydrologic input file includes inputs of flow from the North Yuba, Middle Yuba, and South Yuba rivers; and Oregon, Deer, and Dry creeks; and accretions downstream of the flow input locations. The model writes daily output to a separate, user specified HEC-DSS file. The model includes operations to both determine and adjust New Bullards Bar Reservoir releases to meet an end-of-september New Bullards Bar Reservoir carryover storage target. If simulated end-of-september New Bullards Bar Reservoir storage is forecasted to be less than the target, agricultural delivery releases from New Bullards Bar Reservoir and corresponding diversions at Daguerre Point Dam are reduced until either the forecasted storage meets the target or deliveries are reduced to a user-specified minimum amount. The model also includes the ability to compute the NYI and operate for Accord flow requirements in the Yuba River below Englebright Dam. Computation of the NYI includes perfect foresight for inflows for the upcoming water year. The volume of inflow is added to the volume of operable storage in New Bullards Bar Reservoir on September 30 to determine the NYI value. Based on the NYI, the model computes the appropriate flow requirement for both the Yuba River near Smartsville gage and the Yuba River near Marysville gage by date. Any resulting change in Accord minimum instream flow schedules are made on April 1 of the current water year. The model uses historic inflows into the Project, but includes the ability for a user to modify the inflow data set. The model includes the ability for New Bullards Bar Reservoir releases to reflect daily operations for the power market. If a specific pattern of weekly operations is desired, the model will first simulate Project operations without any reflection of market conditions, and then will revise New Colgate Powerhouse releases and Englebright Reservoir storage to reflect preferred operations to respond to biased day of week preference to simulate market conditions. Releases from the Narrows 1 and Narrows 2 powerhouses are maintained from the initial simulation, and changes to New Colgate Powerhouse operations are subject to limitations on Englebright Reservoir storage. The model also includes the ability for the user to specify a preference for either the Narrows 1 or Narrows 2 powerhouse for releases from Englebright Reservoir. This choice does not affect the total volume released to the Yuba River below Englebright Dam, but it can affect the hydropower generation amount at each powerhouse and the total combined generation amount. For a Narrows 1 Powerhouse preference, Narrows 1 Powerhouse is used as much as possible, and the Narrows 2 Powerhouse is used when needed. For the Narrows 2 Powerhouse preference, the Narrows 2 Powerhouse is used as much as possible, and the Narrows 1 Powerhouse is only used when needed. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 16 of , Yuba County Water Agency

25 An initial version of the model was provided to the Relicensing Participants on a compact disk at a meeting on June 14, At the time of the writing of this Technical Memorandum, two subsequent updates to the Model to incorporate changes to respond to comments by Relicensing Participants, were provided on July 24, 2012, and August 13, Model Validation The model validation process included the comparison of simulated output. Key output for each of the major validation parameters is included below. A complete set of validation output is provided in Attachment 2-2B End-of-Day New Bullards Bar Reservoir Storage Figure is a plot of historical and modeled New Bullards Bar Reservoir storage for the 3- year validation simulation. Figure Storage in New Bullards Bar Reservoir. Figure is a plot of storage in New Bullards Bar Reservoir for the 10-year simulation period. The modeled storage does not reach the low storage seen historically at the end of WYs 2002 and 2004 because of additional releases of water for power generation in spring and early summer in these years to respond to critical power shortages in the California power market. The modeled lower storage in late WYs 2006 through 2007 is a result of a transfer release that was made in 2006, which has not been modeled. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 17 of 32

26 Figure Storage in New Bullards Bar Reservoir for Water Year 2001 through Daily Average Releases from New Colgate Powerhouse Figure shows the historical and modeled mean daily releases at New Colgate Powerhouse (USGS gage ) for WYs 2008 through A 7-day moving average trend line of the historical release is also plotted. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 18 of , Yuba County Water Agency

27 Figure Mean Daily New Colgate Powerhouse Release (USGS gage ) with 7 day moving average of historical releases Daily Average Middle Yuba River Flow Below Our House Diversion Dam Figure is a semi-log graph of mean daily flow at USGS stream gage , located immediately downstream of Our House Diversion Dam, as well as modeled mean daily flows for this location. Figure Mean Daily Flow at Below Our House Dam (USGS gage ). November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 19 of 32

28 3.2.4 Daily Average Yuba River Flow at Smartsville Figure shows historical and modeled mean daily flows at the Smartsville gage (USGS gage ) located several hundred feet downstream of Englebright Dam and downstream of the Narrows 1 and Narrows 2 powerhouses. Figure Mean Daily Flows below Englebright Dam (USGS gage ) Daily Average Yuba River Flow at Marysville Mean daily flows at Marysville as measured at the USGS gage (USGS gage ) and from the model are shown in Figure Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 20 of , Yuba County Water Agency

29 Figure Mean Daily Flow at Marysville Gage (USGS gage ). 3.3 Base Case Scenario The Base Case Scenario is intended to represent conditions as they currently exist, with the current rules, regulations, water supply demands, and operational practices. The historical inflows and synthetic accretions within the Project area were used in the Base Case Scenario. A detailed description of the Base Case Scenario is provided in Attachment 2-2C, which provides a description of the general assumptions, regulatory requirements and agreements, water supply demands, and other Project considerations included within the Base Case Scenario. The Base Case Scenario includes a representation of the regulatory requirements affecting Project operations. Regulatory requirements included in the Base Case Scenario are: Project flow and ramping rate requirements Yuba River Accord flow requirements (SWRCB 2008) USACE New Bullards Bar flood control requirements (USACE 1972) The Base Case Scenario also includes a representation of current agricultural irrigation demands served by the Project, and current operations of non-ycwa Projects upstream from the Project. Last, the Base Case Scenario includes a representation of Project operational practices such as New Bullards Bar Reservoir target operating line operations, New Bullards Bar Reservoir carryover storage operations, New Colgate Powerhouse operations, and Narrows 2 Powerhouse operations. A summary of the Base Case Scenario assumptions was presented to the Relicensing Participants on June 24, November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 21 of 32

30 Table provides a summary of the assumptions used in the Base Case Scenario. For a complete description of the assumptions, see Attachment 2-2C. Table Base Case Scenario modeling assumptions. Location Basics Middle Yuba River Oregon Creek New Bullards Bar Reservoir Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Starting Agricultural Delivery Deficiency: 0% Inflow: Historical above Our House Dam Accretions: Synthetic Minimum Flow below Our House Dam (cfs): Per FERC 2246 License June 16-April 14: 30 April 15-June 15: 50 Minimum Flow Buffer (cfs): 3 Lohman Ridge Tunnel Capacity (cfs): 860 Ramping Rate (cfs): Inflow: Accretions: None Historical above Log Cabin Dam Synthetic Minimum Flow below Log Cabin Dam (cfs): Per FERC 2246 License June 16-April 14: 8 April 15-June 15: 12 Minimum Flow Buffer (cfs): 1 Camptonville Tunnel Capacity (cfs): 1,100 Ramping Rate (cfs): Inflow: None Accretions: Synthetic New Bullards Bar Reservoir Gross Pool Elevation (feet above mean sea level): 1,956 New Bullards Bar Reservoir Gross Pool Storage (ac-ft): 966,103 New Bullards Bar Reservoir Minimum Pool Storage (ac-ft): Historical at Goodyears Bar Historical below Slate Creek Diversion Dam Per FERC 2246 License 234,000 New Bullards Bar Reservoir Flood Reservation (TAF): Per 1972 USACE Flood Control Manual October 31-March 31: 170 April 30: 100 May 31-September 15: 0 Linearly interpolated for intermediate dates Flood Reservation Space Buffer (ac-ft): 8,000 Minimum Flow below New Bullards Bar Dam (cfs): Per FERC 2246 License Year-Around: 5 (from New Bullards Bar Minimum Flow Hydro) Minimum Flow Buffer (cfs): 2 Maximum Flow below New Bullards Bar Dam (cfs): Ramping Rate: Per 1972 USACE Flood Control Manual 50,000 Spillway Elevation-Release Capacity: Maximum Per 1972 USACE Flood Control Manual New Bullards Bar Reservoir Target Storage (ac-ft): September 30: 650,000 October 31: 660,000 None Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 22 of , Yuba County Water Agency

31 Table (continued) Location (continued) New Bullards B Reservoir (continued) Inflow: 660,000 December 31: 650,000 January 31: 600,000 February 28: 650,000 March 31: 750,000 April 30: 850,000 May 31: 940,000 June 30: 920,000 July 15: 875,000 July 31: 825,000 August 15: 770,000 August 31: 715,000 Linearly interpolated for intermediate dates New Bullards Bar Reservoir Target Storage Buffers (Upper/Lower) (ac-ft): Reservoir Evaporation (inches): Carryover Storage Drought Protection: September 30: 20,000 /10,000 October 31: 20,000 /10,000 November 30: 30,000 /30,000 December 31: 30,000 /30,000 January 31: 80,000 /30,000 February 28: 30,000 /30,000 March 31: 30,000 /30,000 April 30: 30,000 /30,000 May 31: 26,000 /100,000 June 30: 0 / 80,000 July 15: 5,000 /60,000 July 31: 10,000 /40,000 August 15: 10,000 /35,000 August 31: 10,000 /15,000 October: 4.31 November: 1.67 December: 1.04 January: 0.93 February: 1.70 March: 2.44 April: 3.21 May: 4.13 June: 6.48 July: 7.78 August: 7.24 September: 5.08 Linearly interpolated for intermediate dates 99% exceedance (1 in 100 year) Carryover Storage Delivery Protection: 50% of following year Minimum Shortage for Current Year for Carryover Storage: 50% Instream Flow Requirement for Following Year: Yuba Accord Schedule 6 Maximum Carryover Storage Volume (TAF): 440 Carryover Storage Buffer (TAF): 45 Annual Evaporation for Carryover Storage Calculation (TAF): 15 Yuba County Water Agency November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 23 of 32

32 Table (continued) Colgate Powerhouse Colgate Powerhouse Release Capacity (cfs): 3,430 Colgate Powerhouse Minimum Release (cfs): 0 Colgate Powerhouse Turbine Elevation (feet above mean sea level):: 565 Maximum Colgate Powerhouse Reduction for Englebright Reservoir Spill Avoidance: 30% (preserve 70% of original releases) Colgate Powerhouse Flow-Head-Generation: Based on empirical data ( ) Colgate Powerhouse Generation Factors Applied: None Ramping Rate: None Location (continued) Englebright Reservoir Inflow: Accretions: Synthetic Englebright Dam Crest Elevation (feet above mean sea level):: 527 Englebright Reservoir Minimum Operating Elevation (feet above mean sea level):: 516 Englebright Reservoir Target Operating Elevation (feet above mean sea level):: 519 Englebright Reservoir Target Operating Storage (ac-ft): 30,947 Historical South Yuba River at Jones Bar Englebright Reservoir Stage Storage Curve: As provided by YCWA 5/10/2012 Englebright Reservoir Stage Spill Relationship: As provided by YCWA 5/10/2012 Narrows 1 Powerhouse Maximum Release Capacity (cfs): 720 Narrows 1 Powerhouse Minimum Release (cfs): 71 Narrows 2 Powerhouse Maximum Release Capacity (cfs): 3,400 Narrows 2 Powerhouse Minimum Release (cfs): 900 Narrows 1 Powerhouse Flow Head-Generation Relationship: Developed based on PG&E flow test Narrows 2 Powerhouse Flow Head-Generation Relationship: Based on empirical data ( ) Narrows 1 and 2 Powerhouses' Tailwater Elevation (feet above mean sea level):: 287 Elevation trigger for Maximum Narrows Release (feet above mean sea level):: 523 Narrows 1 and 2 Powerhouses Flow Split: Favor use of Narrows 1 powerhouse for "Green Energy Credits" Englebright Reservoir Water Surface Area (acres): 810 Reservoir Evaporation (inches): Number of Days Forward to Look for Forecasting Freshets (days): October: 5.03 November: 1.95 December: 1.21 January: 1.09 February: 1.99 March: 2.85 April: 3.75 May: 4.83 June: 7.58 July: 9.09 August: 8.46 September: Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 24 of , Yuba County Water Agency

33 Table (continued) Location (continued) Other Assumptions Lower Yuba River Inflow: Accretions: Minimum Flow at Smartville Gage: Smartsville Gage Buffer: Minimum Flow at Marysville Gage: Marysville Gage Buffer: Maximum Flow at Marysville gage: Daguerre Point Diversion Demand: Groundwater Substitution Transfers: Flow Stability Criteria: Maximum Flow Above Minimum Flows for September 1- October 31 (cfs): Ramping Rate (cfs): Englebright Spill Avoidance: New Bullards Bar Reservoir Target Operating Line Operations: Instream flow Requirements: Low New Bullards Bar Reservoir Storage: Historical Deer Creek near Smartville Synthetic Dry Creek near confluence None Per Yuba River Accord None, Accord flow schedules applied on a 5-day average Per Yuba River Accord None, Accord flow schedules applied on a 5-day average Per 1972 USACE Flood Control Manual 120,000 cfs Based on 2005 land use and published applied water rates Daily patterns based on historical deliveries Present Level Demands (291,197 ac-ft wet/ 305,081 ac-ft Dry) Per Yuba Accord, 30 TAF in Schedule 6 years Per FERC 2246 License Amendment Only applies to controlled events Maximum reduction to 70% of previous day's flow Maximum reduction to 55% of September 15-October 31 flow Maximum reduction to 65% of November 1-March 31 flow 300 Maximum daily reduction of 200 cfs If forecasted inflow to Englebright Reservoir (assumes 4 days of perfect foresight) exceeds Narrows 1 and 2 combined release capacity, reduce Colgate generation to create space in Englebright Reservoir as long as it does not result in New Bullards Bar Reservoir encroaching on its flood reservation. If forecasted storage, with operations for instream flows, would result in New Bullards Bar Reservoir storage in excess of upper target operating line buffer (but below flood pool), run Colgate Powerhouse at maximum capacity, providing it does not spill Englebright Reservoir. If forecasted storage would be below lower target operating line buffer (but above minimum pool), make releases for lower Yuba River flow requirements. Forecasted storage within buffer zone results in releases that are linearly interpolated between the two extremes. Computed assuming perfect foresight for the year. Are in effect for April 1 through March 31 If New Bullards Bar Reservoir storage reaches the FERC minimum pool, inflows are released up to the instream flow requirement. Some operational practices, such as Browns Valley Irrigation District s (BVID) 3,100 ac-ft annual conserved water transfer and YCWA s member unit discretionary groundwater substitution transfers are not included in the Base Case Scenario. While YCWA helps facilitate these practices, they are not YCWA operations. Similarly, some regulatory practices, such as the 2012 United States Department of Commerce, National Oceanic and Atmospheric Association, National Marine Fisheries Service s (NMFS) Biological Opinion on USACE s continued operation and maintenance (O&M) of Englebright and Daguerre Point dams are not included in the Base Case Scenario since they do not affect the way Project operations would be modeled. November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 25 of 32

34 Senior water rights of downstream water purveyors such as BVID, Cordua Irrigation District, and Hallwood Irrigation Company are reflected in the representation of the irrigation diversions from Daguerre Point Dam. Water rights of riparian users from the Yuba River below Englebright Dam have been included in previous modeling of YCWA operations, but are not included in this model since those diversions no longer occur. 3.4 Model Documentation After completion of the Model development, a Model Development Report was written, describing the model development process, the model inputs and outputs, the modeling approach, and a summary of the assumptions included in the Model. The Model Hydrology Report was concurrently written, describing the method used to develop the period of record for input hydrology for the Model. The Model Hydrology Report also includes a comparison of synthetic with historical flows, both on a short-term and long-term basis. This report was provided to the Relicensing Participants on July 24, 2012, and there were several subsequent meetings to discuss the Relicensing Participants questions or comments about the report. Through discussion with the Project operators, the Base Case Report was developed to document the Base Case scenario conditions. The Base Case Report includes a detailed discussion of the regulatory constraints affecting the Base Case Scenario, along with key assumptions associated with the Base Case Scenario. The report also includes a tabular summary of these assumptions, and a graphical presentation of selected model output. 4.0 Discussion The following section provides a discussion of the various elements of the Water Balance/Operations Model. 4.1 Model Development After selection of the model platform, the development of the model occurred over approximately 2 years, with the majority of the time spent running a wide range of scenarios and working out minor variances from expected results. During the model development period, a substantial amount of time was spent on the development of the input hydrology, or more specifically, on the accretions to the Project below the primary stream gaged inflow locations. Of particular concern were differences in total accretions to New Bullards Bar and Englebright Reservoirs between methods for synthesizing the inflow hydrology. YCWA was interested in maintaining a general, physically-based approach rather than manipulating short periods to fit known data. YCWA s approach was supported by the belief that there was inherent error in available historical gaged data. The rationale for using the selected method was that if synthetic accretion volumes were within a reasonable range of the alternate method including standard ranges of stream gaging error, the accretions would be valid. Period-of-record accumulated accretions to both New Bullards Bar and Englebright reservoirs were compared against their respective historical mass-balance Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 26 of , Yuba County Water Agency

35 derived accretions and the long-term results indicated a reasonable match; variances could be explained by small, yet persistent bias in gaging at major flow measurement locations, such as within the New Colgate penstock, or at the Yuba River near the Smartsville gage. The Hydrology Report is attached to this technical memorandum as Attachment 2-2D. Other challenges associated with the development of the model included the refinement of the methodology used to define the New Bullards Bar Reservoir target operations storage range, used when hydrology is sufficiently wet that the system is not solely driven by flow requirements. The original methodology included a simple monthly storage target, but this resulted in excessive oscillation in reservoir releases as storage would go from below the target line, where minimum flow requirements would control; to above the target line, where releases were made to reduce New Bullards Bar Reservoir storage to the target line. The solution was to include a buffer range, where releases would be determined by a linear interpolation between releases for minimum flow requirements and releases to meet a storage target. The definition of this range is currently based on the Base Case scenario target operating line and the Yuba Accord, but operations under future flow requirements will likely require tuning of both the target storage line and the buffers around the target storage line to ensure representation of prudent operations and reasonably smooth releases from New Bullards Bar Reservoir and consequently Englebright Reservoir. The model represents Project operations very well, but if the relicensing requires simulation of scenarios that substantially deviate from current operational practices, additional model coding may be required. Sufficient flexibility has been built into the model so that it can be configured for a relatively wide range of operational scenarios, and should be easily adapted to alternative future operation scenarios that may be examined throughout the relicensing. 4.2 Model Validation The Project has been subject to several changing regulatory regimes since 2010, so a reasonable approach for validating the model was done on a short-term basis, where detailed examination of each departure of simulated conditions from historical conditions was scrutinized, and a longterm basis, where overall trends were examined. A close examination of the last 3 years included consulting with operations planners about all differences between historical and simulated flows to ensure each difference could be explained by operational decisions made for a specific event rather than as a standard operational practice. Most differences could be explained by operations for water transfers or for high-flow flood events that were not fully represented in the model. Any difference that was due to a normal operational practice resulted in a modification to the model to include that practice. While the model validation process ensured the model logic was consistent with Project operations, it also served as a validation of the hydrologic input data; the validation process included both examinations of New Bullards Bar Reservoir storage; New Colgate, Narrows 1, and Narrows 2 powerhouses generation; and of flows throughout the system. Inadequacies of the hydrologic input data set would have manifested themselves as either differences in flow or storage in the validation process, but other than in flood-type events, where gages are rarely November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 27 of 32

36 accurate and operations are driven by short-term (i.e., less than 24 hour) decisions, the model represented both recent historical and long-term operations exceptionally well, indicating that both the model logic and input hydrology are valid for use in the relicensing. 5.0 Study-Specific Consultation The study included one study-specific consultation, which is discussed below. 5.1 Consult Regarding Model Development The FERC-approved study states: YCWA will meet with interested Relicensing Participants to review the model. This will include a meeting to generally introduce Relicensing Participants to the model. At that meeting, Relicensing Participants will be given a Compact Disk with an executable version of the model, the Model Development Report describing all model input and logic including priorities, and the Draft Model Validation Report. After a reasonable time for review, YCWA will hold a series of workshops with interested Relicensing Participants to collaboratively review the Model. (Step 4.) YCWA met with interested Relicensing Participants on multiple occasions to discuss the intended approach to developing the model; to discuss the input hydrology for the model; to discuss the general approach for modeling the Project; to distribute the model and associated reports; to discuss the model; and lastly, to respond to questions about the model. Table includes a list of meetings held regarding this model with a brief description of the purpose of the meeting. Table Relicensing Participant meetings for consultation on Operations/Water Balance Model development. Date Meeting Subject 11/12/2009 Description of overall Project operations and intended modeling approach 9/22/2010 Discussion of Water Balance/Operations Model Study Plan 4/28/2011 Discussion of Water Balance/Operations Model input hydrology 11/10/2011 Discussion of Water Balance/Operations Model input hydrology 5/9/2012 Discussion of Water Balance/Operations Model basics and general modeling approach 6/14/2012 Initial distribution of a Compact Disk with the Water Balance/Operations Model, Base Case Scenario, and Validation Scenario 7/24/2012 Model discussion to receive comments on distributed model, to discuss updates to model based on previous comments, and to provide Validation Report and Model Development Report 8/13/2012 Model discussion to receive comments on distributed model, and to discuss updates to model based on previous comments 8/24/2012 Model discussion to receive comments on distributed model. After making the reports publicly available on July 24, 2012, a request for comments on the Validation Report and Model Development Report was sent to the Relicensing Participants on August 10, No comments were received. Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 28 of , Yuba County Water Agency

37 6.0 Variances from FERC-Approved Study Yuba County Water Agency The study was performed in conformance to the FERC-approved study with five exceptions. First, the FERC-approved study stated the model would include both inflows from Dry Creek near its confluence with the Yuba River and from ungaged tributaries to the Yuba River downstream of Englebright Dam. Instead, YCWA consolidated the accretions from these two locations into a single accretion because no consistent, predictable trend for predicting non-dry Creek accretions to the Yuba River below Englebright Dam was identified. Many approaches were examined, but limiting factors included potential gaging error at the Smartsville and Marysville gages; seasonal influences from the Yuba Goldfields; and the relatively flat, yet highly modified geography of the area surrounding the Yuba River made identifying the contributing watershed impossible. Second, the FERC-approved study stated a Microsoft Excel spreadsheet for post-processing daily model output into hourly or 15-minute patterns would be developed. This post-processor was not developed because it was determined through the consultation process with Relicensing Participants that there was no need for a sub-daily timestep. The original intent had been to provide sub-daily flows for use in simulating water temperatures throughout the Project area, but it was determined a daily water temperature was adequate for purposes of analyzing Project effects on water temperatures. Third, the FERC-approved study stated the model would include three options for splitting Englebright Reservoir releases between the Narrows 1 and Narrows 2 powerhouses. The model includes two options, a Narrows 1 Powerhouse preference, and a Narrows 2 Powerhouse preference. A post-relicensing split was considered by the model developers to be too speculative prior to negotiations with PG&E regarding potential post-relicensing generation scenarios. There were no objections or concerns voiced by the Relicensing Participants when this was brought up in meetings. Fourth, the FERC-approved study stated the model would provide output representing both the North Canal and South Canal diversions, but the model aggregates all agricultural diversions into a single diversion point. YCWA decided irrigation deliveries are outside of the range of the relicensing, and for purposes of evaluating the effects of Project operations on flows within the Yuba River, a single timeseries for all agricultural deliveries would be sufficient. There were no objections or concerns voiced by the Relicensing Participants when this was brought up in meetings. Fifth, the study report was completed late due to the quality assurance/quality control review of study results taking longer than anticipated and resulting in a slight delay of study completion. 7.0 Attachments to this Technical Memorandum This technical memorandum includes the following six attachments: November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 29 of 32

38 Attachment 2-2A Model Development Report [1 Adobe pdf file: 3 MB; 64 pages formatted to print double sided on 8 ½ x 11 paper] Attachment 2-2B Model Validation Report [1 Adobe pdf file: 3 MB; 40 pages formatted to print double sided on 8 ½ x 11 paper] Attachment 2-2C Base Case Scenario Report [1 Adobe pdf file: 1 MB; 44 pages formatted to print double sided on 8 ½ x 11 paper] Attachment 2-2D Hydrology Report [1 Adobe pdf file: 2 MB; 72 pages formatted to print double sided on 8 ½ x 11 paper] Attachment 2-2E Water Balance/Operations Model Configured in the Base Case Scenario and in the Validation Scenario dated November 2012 [1 CD with the Base Case model and input file, the validation input and output files: 4.DSS files and 3 Excel files, 26.6 MB] Attachment 2-2F Hydrologic Data Set [1 DVD with the following six folders: 1) DSS files (5.DSS files, 37.6 MB) ; 2) Exceedance Plots (2 Excel files, 31 MB; and 2 Adobe pdf files, 23.9 MB); 3) Hydrology Development (3 Excel files, 48.1 MB); 4) Stage Storage Curves (2 Excel files, 151 MB); 5) Unimpaired Flow (2 Excel files, 12 MB; and 1 DSS file 315 KB); and 6)Water Year Types (5 Excel files and 1.DSS file, 6.2 MB). 8.0 References Federal Power Commission (FPC) Order Issuing License and Accepting Surrender of License. May P FPC Order Amending License (Major). FPC, Washington DC. May 6, Federal Energy Regulatory Commission (FERC) Order Modifying and Approving Amendment of License. November Rykiel, Edward J Testing Ecological Models: the Meaning of Validation. August State of California Department of Water Resources Order WR Order Approving Petition for Modification and Petition for Long-Term Transfer of Water. March United States Army Corps of Engineers (USACE) New Bullards Bar Reservoir Reservoir Regulation for Flood Control. June Yuba County Water Agency (YCWA) Draft Environmental Impact Report/ Environmental Impact Statement for the Proposed Lower Yuba River Accord. June 2007 Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 30 of , Yuba County Water Agency

39 . 2012a. Model Development Report, July b. Validation Report, July c. Base Case Report, July d. Hydrology Report, July November 2012 Technical Memorandum 2-2 Water Balance/Operations Model 2012, Yuba County Water Agency Page 31 of 32

40 Page Left Blank Water Balance/Operations Model Technical Memorandum 2-2 November 2012 Page 32 of , Yuba County Water Agency

41 Technical Memorandum 2-2 Water Balance/Operations Model Attachment 2-2A Model Development Report November , Yuba County Water Agency All Rights Reserved

42

43 Table of Contents Section No. Description Page No. 1.0 Introduction... A History of the... A Need for a Model... A Previous Modeling Efforts... A Yuba River Watershed Hydrology... A Primary Tributaries... A North Yuba River... A Middle Yuba River... A South Yuba River... A Yuba River... A Minor Tributaries... A Slate Creek... A Oregon Creek... A Deer Creek... A Canyon Creek... A Dry Creek... A Summary of Hydrology... A Facilities... A New Bullards Bar Dam and Reservoir... A New Colgate Powerhouse... A Englebright Dam and Reservoir... A Narrows 1 and 2 Powerhouses... A Our House Dam... A Lohman Ridge Tunnel... A Log Cabin Dam... A Camptonville Tunnel... A Daguerre Point Dam... A Agricultural Demands... A Member Units... A Brophy Water District... A Browns Valley Irrigation District... A Cordua Irrigation District... A Dry Creek Mutual Water Company... A Hallwood Irrigation Company... A Ramirez Water District... A South Yuba Water District... A-17 Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page TOC-i

44 Table of Contents (continued) Section No. Description Page No Wheatland Water District... A Delivery Demands... A Diversion Shortage Provisions... A Model Overview... A Platform Selection... A Modeling Basics... A Timestep... A YRDPM Model Coverage... A Inputs... A Outputs... A Incorporation of Changes in Upstream Project Operations... A Characterization of Physical Facilities... A Our House Dam and Lohman Ridge Tunnel... A Log Cabin Dam and Camptonville Tunnel... A Slate Creek Diversion Dam... A New Bullards Bar Reservoir... A Reservoir Releases... A Power Generation... A Evaporation... A Englebright Reservoir... A Reservoir Releases... A Power Generation... A Reservoir Evaporation... A Characterization of Operational Rules... A Our House Dam Operations... A Instream Flow Requirements... A Diversions... A Log Cabin Dam Operations... A Instream Flow Requirements... A Diversions... A Slate Creek Diversion Dam Operations... A Historical Flows... A Slate Creek Only... A New Bullards Bar Reservoir Operations... A Flood Management... A Target Operating Line... A-42 Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page TOC-ii 2012, Yuba County Water Agency November 2012

45 Table of Contents (continued) Section No. Description Page No Carryover Storage... A Inactive Pool... A Englebright Storage... A Power Generation... A Englebright Reservoir Operations... A Instream Flow Requirements... A Flood Management... A Power Generation... A Daguerre Point Dam Deliveries... A Water Transfers... A Stored Water Transfers... A Groundwater Substitution Transfers... A Released Transfer Water... A Implementation of Transfers in Modeling... A Model Simulation Process... A References... A-56 List of Figures Figure No. Description Page No Facilities Location.... A Yuba River Watersheds... A Yuba River Watershed and Sub-Basin... A Sources of project hydrology... A Reaches.... A New Colgate Powerhouse Load-Flow Curve at Gross Head 1,396 ft... A New Colgate Efficiency Curve at Gross Head 1,396 ft... A Narrows 2 Powerhouse Load-Flow Curve at Gross Head 240 ft... A Narrows 2 Efficiency Curve at Gross Head 240 ft... A-37 List of Tables Table No. Description Page No Synthetic annual delivery demand for YCWA Member Units.... A Yuba County Water Agency Water Supply Contracts Deficiency Provisions... A YRDPM Hydrologic Input Data and DSS Names... A Operations Inputs for the YRDPM... A-24 Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page TOC-iii

46 List of Tables (continued) Table No. Description Page No YRDPM Output and DSS Names... A New Bullards Bar Reservoir Maximum Release... A New Bullards Bar Reservoir Monthly Evaporation Factors... A Maximum Englebright Reservoir Release by Elevation... A Englebright Reservoir Monthly Evaporation Factors... A New Bullards Bar Reservoir Flood Reservation Storage... A Example New Bullards Bar Reservoir Storage Target Operating Line and Buffers... A Englebright Reservoir Operations Flags... A Yuba County Water Agency historical sales 1987 to A Yuba County Water Agency historical groundwater substitution pumping (ac-ft).... A Historical monthly release volumes of groundwater substitution transfers.... A Monthly pattern of historical water transfers.... A-53 Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page TOC-iv 2012, Yuba County Water Agency November 2012

47 1.0 Introduction This report describes the development of the Water Balance and Operations Model developed for Yuba County Water Agency s (YCWA or Licensee), Federal Energy Regulatory Commission (FERC) Project No (YRDP or Project), Relicensing. 1.1 History of the YCWA, located in Marysville, California, is a public agency formed in 1959 pursuant to the Yuba County Water Agency Act (West s Water Code App to 84-28). Section 4.1 of this Act (West s Water Code App ) authorizes YCWA to developand sell hydroelectric power. Section 5.1 of this Act (West s Water Code App ) authorizes YCWA to enter into contracts with its member units for various purposes, including the sale of water. Sections 4.3, 4.4 and 4.5 of this Act (West s Water Code App , & ) authorize YCWA to to develop and operate water resource projects. Besides numerous water delivery conduits, YCWA owns and operates the Yuba River Development Project, which is located in Yuba County, California, on the Yuba River and its tributaries including the North and Middle Yuba River and Oregon Creek. A portion of the area within the FERC Project Boundary is located on federally-owned land managed by the United States Department of Agriculture (USDA), Forest Service (Forest Service) as part of Plumas and Tahoe national forests. Project construction started in late 1966 and continued to early 1970 when the New Colgate Powerhouse began producing electricity. At about this time the Narrows 2 Powerhouse also went on-line and began producing electricity. By the summer of 1970 the Project was operational, YCWA had taken ownership of the Project and it was producing electricity and regulating the flows of the Yuba River. YCWA holds the initial FERC license for the Project, which was issued to YCWA by the Federal Power Commission (FPC), FERC s predecessor, on May 16, 1963 (FPC 1963). The initial license was effective on May 1, 1963 for a term ending April 30, 2016 (FPC 1966). The Project consists of three developments New Colgate, New Bullards Bar Minimum Flow, and Narrows No. 2 which, in total, include: 1 main dam; 2 diversion dams; 4 water tunnels; 3 powerhouses with associated switchyards with a combined capacity of megawatts (MW); and appurtenant facilities and structures. Figure shows the location of the Project facilities. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-1

48 Figure Facilities Location. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

49 1.2 Need for a Model A water balance/operations model is needed to simulate the operations of the Project under historical or synthesized hydrology and output resulting physical changes on the affected basin. A primary objective for developing a model is so that information provided by the model output can be used by all Relicensing Participants during the Relicensing to simulate current and potential future operations of the Project. Model development must be done in a fashion that results in all interested Relicensing Participants agreeing the model is reasonably reliable for the purposes of Relicensing, and agreeing to use this single water balance/operations model to make Relicensing recommendations. Objectives include developing a model that simulates Project operations for a period of analysis that covers a range of hydrologic conditions. The water operations model should also be capable of meeting the following criteria: Reflect operational decisions for flood control; water supply; recreation; stream flows; and hydropower generation. Accurately reproducing observed reservoir levels, reservoir releases, and hydropower generation, within acceptable calibration standards over a range of hydrologic conditions Providing output to inform other studies, analyses, and models Allowing simulation of changes in Project operations to determine effects on reservoir levels, reservoir releases and hydropower generation 1.3 Previous Modeling Efforts The first model of the Yuba Basin was developed by the Department of Water Resource s (DWR) Division of Planning (now named the Bay-Delta Office) using the U.S. Army Corps of Engineers (USACE), Hydraulic Engineering Center (HEC) HEC-3 program to generate inflows for DWR s planning model, DWRSIM, for the State Water Project (Yuba River Watershed Model, DWR 1985). Between 1988 and 2002, Bookman-Edmonston Engineering, Inc., on behalf of YCWA, collaborated with DWR to further refine and develop this model. Bookman-Edmonston Engineering, Inc. moved the model from the HEC-3 to the HEC-5 software platform, and modified operational parameters and criteria to better characterize YCWA operations. The HEC-5-based Yuba River Basin Model simulates the entire Yuba River watershed, including facilities outside of YCWA s operational control. Detailed information regarding the HEC-5 model is presented in the Yuba River Basin Model: Operations and Simulation Procedures Report (YCWA 2000) prepared for the State Water Resources Control Board (SWRCB) Lower Yuba River Hearings in In 2002, MWH Global, Inc. developed the Yuba Project Model, a monthly time step spreadsheet model of the Yuba Project and the Yuba River below Englebright Dam on the behalf of YCWA. Inflows to New Bullards Bar and Englebright reservoirs, and flows from Deer Creek to the Yuba Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-3

50 River were obtained from the output of the HEC-5 Yuba River Basin Model. The Yuba Project Model was subsequently used to evaluate flow conditions in the Proposed Lower Yuba River Accord Draft Environmental Impact Report/Impact Statement (YCWA 2007). 2.0 Yuba River Watershed Hydrology The Yuba River watershed drains approximately 1,339 square miles (sq-mi) (United States Geologic Survey [USGS] 2004) of the western slope of the Sierra Nevada, including portions of Sierra, Placer, Yuba, and Nevada counties, as shown in Figure The Yuba River is a tributary of the Feather River, which in turn is a tributary of the Sacramento River. The watershed rises from an elevation of about 60 feet (ft) to about 8,590 ft above mean sea level (ftmsl). The annual unimpaired flow below Englebright Dam, as measured by the USGS at the Smartsville Gage (USGS gage ) on the Yuba River has ranged from a high of 4.93 million acre-feet (MAF) in 1982 to a low of 0.37 MAF in 1977, with an average of about 2.36 MAF per year (1901 to 2010). 1 In general, runoff is nearly equally divided between runoff from rainfall during October through March and runoff from snowmelt during April through September. 1 The forecasted seasonal unimpaired flow at Smartsville is estimated each year by DWR and reported monthly in Bulletin 120, Water Conditions in California. The unimpaired flow at Smartsville is used in YCWA contracts for water delivery to senior water right holders on the lower Yuba River, and is used in the calculation of the Yuba River Index, a hydrologic water year type index for the Yuba River, defined in State Water Resources Control Board Revised Decision Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

51 Source: MWH Americas, Inc. Figure Yuba River Watersheds. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-5

52 2.1 Primary Tributaries The three primary Yuba River tributaries are the North Yuba River, the Middle Yuba River, and the South Yuba River. The Yuba River begins at the confluence of the North Yuba and Middle Yuba rivers two miles (mi) below New Bullards Bar Dam river mile (RM) 2.4. The South Yuba River flows into the Yuba River approximately 10 mi downstream of the head of the Yuba River (RM 41.0). This section provides a description of these three primary Yuba River tributaries and the Yuba River. Figure is a map of the sub-basins that make up the Yuba River watershed. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

53 Source: MWH Americas, Inc. Figure Yuba River Watershed and Sub-Basin. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-7

54 2.1.1 North Yuba River The upper extent of the North Yuba River is at Yuba Pass (elevation 6,701 ft) near State Highway 49 in Sierra County. The river flows parallel to the state highway as far as Downieville, where it diverges from the Highway and flows westward into New Bullards Bar Reservoir. The North Yuba River terminates at its confluence with the Middle Yuba River, approximately two mi downstream of New Bullards Bar Dam, at which point the combined flow of the two rivers becomes the Yuba River. The area of the North Yuba River watershed is approximately 491 sq-mi, and includes portions of Yuba, Sierra, and Plumas counties. The North Yuba River watershed is a predominantly snow-melt driven stream, with peak flows occurring in March through May Middle Yuba River Flows in the Middle Yuba originate from snowmelt and rainfall runoff above the main upper watershed impoundment, Nevada Irrigation District s Jackson Meadows Reservoir, in Sierra County. Most of the upper reaches of the Middle Yuba River are contained in narrow, steep canyons until the river reaches YCWA s 75-ft-high Our House Dam, located southwest of Camptonville near the Sierra/Nevada County line. Approximately 13 mi below Our House Dam, the Middle Yuba River joins the North Yuba River to form the headwaters of the Yuba River. The Middle Yuba River watershed, including Oregon Creek, covers approximately 210 sq-mi, with elevations ranging from 1,120 ft msl to 7,200 ft msl. There are several impairments on the upper Middle Yuba River which are part of Nevada Irrigation District s (NID) Yuba-Bear Hydroelectric Project (FERC Project No. 2266). A portion of Middle Yuba River flows are diverted into the South Yuba River basin by the Milton Diversion Dam (RM 26.8) through the Yuba-Bear Project s Milton-Bowman Tunnel. The Yuba-Bear Project has minimum instream flow requirements below the Milton Diversion Dam. Releases from the Milton Diversion Dam and runoff from sub-basins below Milton Diversion Dam flow to Our House Dam. Inflow at the Our House Dam is partially diverted to Oregon Creek through the Lohman Ridge Tunnel. Oregon Creek joins the Middle Yuba River approximately 8.5 mi below Our House Dam; the combined flow of the two tributaries joins with the North Yuba River approximately 5 mi downstream of the Middle Yuba River s confluence with Oregon Creek. Approximately 23 sqmi of the Middle Yuba River watershed lies below Our House Dam along the Middle Yuba River South Yuba River The headwaters of the South Yuba begin at 9,000 ft in Placer County near Castle Peak and Donner Lake. The South Yuba River is subject to multiple upstream impairments before it joins the Yuba River at Englebright Reservoir. The primary upstream impairments are NID s Yuba Bear Hydroelectric Project, and Pacific Gas and Electric Company s (PG&E) Drum-Spaulding Project (FERC Project No. 2310). Flow from the South Yuba is diverted into the Bear and American River basins via the Drum Canal and South Yuba Canal. Remaining South Yuba River flow joins the Yuba River at Englebright Reservoir. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

55 2.1.4 Yuba River The Yuba River begins at the confluence of the North and Middle Yuba rivers, approximately 16 mi upstream of USACE s Englebright Dam at an elevation of approximately 1,124 ft. The river then extends approximately 24 mi below USACE s Englebright Dam to the Feather River in Marysville. The Yuba River sub-basin covers approximately 95 sq-mi. 2.2 Minor Tributaries Several smaller tributaries flow into the three primary Yuba River tributaries. While the majority of these minor tributaries do not notably contribute to flows in the Yuba River, several are large enough to require consideration in Project hydrologic modeling. Those tributaries include the following: Slate Creek Oregon Creek Deer Creek Canyon Creek Dry Creek The subbasins for each of these minor tributaries are described below Slate Creek Slate Creek originates near the town of La Porte, in the northern portion of the Yuba River watershed. The Slate Creek watershed is approximately 61 sq-mi. The South Feather Water and Power Agency (SFWPA) diverts flows from Slate Creek to the Feather River basin near Strawberry Valley via the Slate Creek Tunnel approximately 9 mi upstream from Slate Creek s confluence with the North Yuba River. The Slate Creek Tunnel has a maximum capacity of 848 cubic feet per second (cfs). Slate Creek joins the North Yuba River approximately a half mile upstream of the upper reaches of New Bullards Bar Reservoir Oregon Creek Oregon Creek is entirely contained within the Middle Yuba River watershed, and originates near elevation 4,455 ft-msl. YCWA s 55-ft-high Log Cabin Dam diverts flows from Oregon Creek to New Bullards Bar Reservoir via the Camptonville Tunnel. Log Cabin Dam is approximately four mi upstream of Oregon Creek s confluence with the Middle Yuba River. Oregon Creek flow above Log Cabin Dam is a combination of outflow from the Lohman Ridge Tunnel, originating at Our House Dam on the Middle Yuba River, and Oregon Creek flows. Above the outfall of the Lohman Ridge Tunnel, Oregon Creek is free of impairments. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-9

56 2.2.3 Deer Creek Deer Creek originates in Nevada County, and in addition to natural runoff, receives flows from the South Yuba River from PG&E s Drum-Spaulding Project. Its natural flows are augmented by diversions from the South Yuba River via the South Yuba Canal. Similarly, several canals divert flow from Deer Creek to the Bear River watershed. Before it flows into the Yuba River near Smartsville, below Englebright Lake, Deer Creek is subject to impoundment at NID s Scotts Flat Reservoir and in Lake Wildwood Canyon Creek Canyon Creek, flowing into the North Yuba River above Slate Creek and below the Goodyears Bar Gage, collects runoff from both Yuba and Sierra counties. The Canyon Creek watershed is ungaged and devoid of any impairment Dry Creek Dry Creek flows near the western edge of Yuba County; its watershed is approximately 108 sqmi, with its headwaters near the town of Challenge at elevation 3,155 ft. Flowing generally southward, Dry Creek flows are captured by the Browns Valley Irrigation District s (BVID) Merle Collins Reservoir, a 57,000 acre-foot (ac-ft) reservoir formed by Virginia Ranch Dam. Dry Creek is approximately 12 mi long from Virginia Ranch Dam to the confluence with the Yuba River. Dry Creek releases from Merle Collins Reservoir are augmented by accretions from local runoff and agricultural return flows, flowing into the Yuba River approximately 10 mi below Englebright Dam. 2.3 Summary of Hydrology Extensive historical gage data is available for the majority of the Yuba River tributaries. For tributaries and subbasins without available historical gage data, tributary and subbasin flows have been synthesized. Figure shows the hydrologic schematic for the Project, identifying which of the Project inflows are derived from gage data, and which are synthesized data. For a complete description of Project hydrology, see Attachment 2-2D. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

57 Source: MWH Americas, Inc. Figure Sources of project hydrology. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-11

58 3.0 Facilities The Project, constructed in the mid-1960s and put into service in the spring of 1970, ranges in elevation from about 300 ft-msl to 2,050 ft-msl. In total, the Project includes: one dam and associated storage reservoir - New Bullards Bar; two diversion dams - Our House and Log Cabin; two diversion tunnels - Lohman Ridge and Camptonville; two power tunnels - New Colgate and Narrows 2; one penstock New Colgate; and three powerhouses - New Colgate, New Bullards Bar Minimum Flow Powerhouse, and Narrows 2. The Project does not include USACE s Englebright Dam and Reservoir or USACE s Daguerre Point Dam. The Project also does not include the Narrows 1 Powerhouse, which is located near the USACE s Englebright Dam and is part of PG&E s Narrows 1 Project (FERC Project No. 1403). 2 However, since these facilities are integral parts of operations of the Projects, these facilities are included in the hydrologic model. 3.1 New Bullards Bar Dam and Reservoir New Bullards Bar Dam is a 1,110 foot-radius, double curvature, concrete arch dam located on the North Yuba River about 2.4 mi upstream of its confluence with the Middle Yuba River. The dam is 645 ft high with a maximum elevation of 1,965 ft-msl. The dam includes one low-level outlet - a 72 inch Hollow Jet Valve, with an invert elevation of 1,395 ft-msl, has a maximum design capacity of about 3,500 cfs at full reservoir pool, and an actual capacity of 1,250 cfs (the release capacity is limited to 1,250 cfs due to valve vibrations at greater release rates). New Bullards Bar Reservoir is the principal storage facility of the Project. The North Yuba River inflow to New Bullards Bar Reservoir is augmented by diversions from the Middle Yuba River to Oregon Creek through the Lohmann Ridge Tunnel, and by diversions from Oregon Creek into New Bullards Bar Reservoir through the Camptonville Tunnel. The average total inflow to New Bullards Bar Reservoir from the North Yuba River and diversions from the Middle Yuba River and Oregon Creek is about 1.2 MAF per year. New Bullards Bar Reservoir is deep, thermally-stratified, and has a retention time of about 6 months. The reservoir is psi-shaped ( ). The narrow center arm, which is the longest of the three arms (i.e., about 13 mi), extends up the North Yuba River to just downstream of the Slate Creek confluence. The slightly wider northeast arm extends upstream about 4 mi, and is formed primarily by Willow and Badger creeks. The northwest arm, the shortest of the three (about 1 mi long) is formed by Little Oregon and Burnt Bridge creeks. The portion of reservoir north of New Bullards Bar Dam near Garden Point is the widest portion of the reservoir (about 2 mi wide). Most of the land surrounding New Bullards Bar Reservoir is primitive with no roads or residential communities. 2 The FERC license for PG&E Narrows 1 Project expires on January 31, 2023 (FERC 2003). Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

59 The reservoir has a gross storage capacity of 966,103 ac-ft with a FERC minimum operating storage of 234,000 ac-ft, leaving 732,103 ac-ft of regulated capacity. YCWA typically operates New Bullards Bar Reservoir by capturing winter and spring runoff from rain and snowmelt for release later in the year. Consequently, New Bullards Bar Reservoir reaches its peak storage at the end of the spring runoff season, and then is gradually drawn down as storage is released to the Yuba River. Releases are made through both the New Bullards Bar Minimum Flow Powerhouse at the base of the dam and to the Yuba River through the New Colgate Power Tunnel and New Colgate Powerhouse on the Yuba River. The reservoir usually reaches its lowest elevation in early to mid-winter. The annual drawdown in normal water years is about 90 ft. The reservoir does not undergo significant daily changes in elevation. New Bullards Bar Reservoir is used to provide irrigation water supply to about 90,000 ac of farmland in western Yuba County. Releases of water from storage are made through the spring and summer to provide flows diverted at USACE s Daguerre Point Dam at RM 11.6 on the Yuba River. Water is released from storage in the fall for diversion at USACE s Daguerre Point Dam for rice stubble decomposition and waterfowl habitat. New Bullards Bar Reservoir is also the main flood control facility for the Yuba River area. 170,000 ac-ft of storage capacity, or approximately 23 percent of the usable capacity of the reservoir, is reserved from October through May for flood protection purposes. In addition to providing flood protection, power, and downstream water supply, YCWA pumps water directly from New Bullards Bar Reservoir to supply water to the Cottage Creek Water Treatment Plant for domestic and recreation uses adjacent to the reservoir. Pumping averages approximately 6 ac-ft per year. This relatively small volume of pumping does not affect Project operations. New Bullards Bar Dam is the fourth dam constructed in the Bullards Bar area. The first dam was a timber crib, rock-filled diversion dam constructed in 1899, and was washed out a year later. In 1900, a 30-ft-tall masonry rock dam was built to replace the washed-out dam. The rock dam is still in place and is located about 1,000 ft downstream of New Bullards Bar Dam. YCWA maintains this dam as a weir for measurement of minimum flow releases from New Bullards Bar Dam. The third dam was a 200-ft-tall concrete-arch dam constructed in 1922 by the Yuba River Power Company, which was acquired by PG&E, and put into operation in That dam, located about one mile upstream of New Bullards Bar Dam in New Bullards Bar Reservoir, was inundated in 1969 when New Bullards Bar Dam began operation and is not normally exposed. 3.2 New Colgate Powerhouse The New Colgate Powerhouse is an above-ground, steel-reinforced, concrete powerhouse located adjacent to the Yuba River at RM The powerhouse contains two Voith Siemens Peltontype turbines with a total capacity of 340 MW under a design head of 1,306 ft and a rated flow of 3,430 cfs. The powerhouse receives water from the New Colgate Power Tunnel and Penstock. The New Colgate Power Tunnel and Penstock is 5.2 mi long and composed of four different types of conveyance structures: an unlined horseshoe tunnel 26 ft square; a lined horseshoe Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-13

60 tunnel 20 ft wide and 14.5 ft high; a lined circular tunnel 14 ft in diameter; and 2,809 ft of steel penstock with a diameter ranging from 9 ft to 14.5 ft. The tunnel and penstock have a maximum flow capacity of 3,500 cfs. 3.3 Englebright Dam and Reservoir Englebright Dam and Reservoir were constructed in 1941 by the USACE to capture sediment produced by upstream hydraulic mining activities. The reservoir is situated downstream of the New Colgate Powerhouse. The average annual inflow to Englebright Reservoir, excluding releases from New Bullards Bar Reservoir, is approximately 400 TAF (thousand acre-feet). Englebright Reservoir has a total storage capacity of approximately 70 TAF, but provides limited conservation storage because the reservoir is used to attenuate- power -peaking releases from New Colgate Powerhouse. Englebright Reservoir is used extensively for recreation. Englebright Dam has no low-level outlet. Water from Englebright Reservoir is released for power generation at the Narrows 1 and Narrows 2 powerhouses, or spilled over the top of the dam. 3.4 Narrows 1 and 2 Powerhouses Narrows 1 Powerhouse, owned by PG&E, is a 12 MW facility, with a discharge capacity of approximately 730 cfs and a bypass flow capacity (when the generator is not operating) of 540 cfs. Narrows 2, which is part of the Project, is a 50 MW facility, with a discharge capacity of approximately 3,400 cfs and a bypass flow capacity of 3,000 cfs. YCWA and PG&E coordinate the operations of Narrows 1 and 2 for hydropower efficiency and to maintain relatively constant flows in the Yuba River below Englebright Dam. 3.5 Our House Dam Our House Diversion Dam is a 130- foot-radius, double curvature, concrete arch dam located on the Middle Yuba River 12 mi upstream of its confluence with the North Yuba River. The dam is 70 ft high with a crest length of 368 ft, a crest elevation of 2,049 ft, and a drainage area of sq-mi. The dam has an impoundment capacity of 280 ac-ft, but storage and water levels do not fluctuate under Project operations. The diversion dam has two outlets: 1) a 5-foot diameter steel pipe controlled by a slide gate on the upstream face of the dam with a maximum capacity of 800 cfs and a centerline elevation of 1,990 ft; and 2) a 24-inch diameter release pipe, with a maximum capacity of 60 cfs and a centerline elevation of 2,000 ft. The diversion dam has a spillway capacity of 60,000 cfs. 3.6 Lohman Ridge Tunnel The Lohman Ridge Diversion Tunnel is 12.5 ft high by 12.5 ft wide, and conveys a maximum flow of 860 cfs through its 19,410 ft length (90% unlined and 10% lined) to Oregon Creek. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

61 3.7 Log Cabin Dam Log Cabin Diversion Dam is a 105-ft-radius, concrete arch dam on Oregon Creek that has a drainage area of 29.1 sq-mi and a maximum spillway capacity of 12,000 cfs. The dam has an impoundment capacity of 90 ac-ft, but storage and water levels do not fluctuate under Project operations. The diversion dam has two outlets: 1) a 5-ft diameter steel pipe controlled by a slide gate on the upstream face of the dam with a maximum capacity is 800 cfs; and 2) an 18-inch diameter release pipe, with a maximum capacity of 13 cfs, located above the low-level outlet and controlled by a downstream gate valve operated by hand. 3.8 Camptonville Tunnel The Camptonville Diversion Tunnel is 6,107 ft long and has the capacity to convey 1,100 cfs of water to New Bullards Bar Reservoir. The first 4,275 ft of the conduit is an unlined, horseshoe tunnel 14.5 ft wide by 14.5 ft high, becoming a lined, horseshoe tunnel 11.7 ft wide by 13 ft high for the remaining 1,832 ft. 3.9 Daguerre Point Dam USACE s Daguerre Point Dam, a weir-type dam, was constructed by the California Debris Commission to prevent hydraulic mining debris from the Yuba River watershed from flowing into the Feather and Sacramento rivers. The dam, which was constructed in 1906 and rebuilt in 1964 following damage from floods, has no appreciable storage capacity. Daguerre Point Dam is used by YCWA to provide for gravity diversion of agricultural water supply to its Member Units. Releases to the Yuba River below the dam are made either through a fish ladder at each end of the dam or over the dam s crest. 4.0 Agricultural Demands Various water districts, irrigation districts, and mutual water companies have contracts with YCWA for delivery of water. Some of the parties that receive water from YCWA also have their own appropriative rights for diversion of water from the Yuba River. This section provides an overview of the agricultural water demands met by the Project. 4.1 Member Units Water diverted under YCWA s water right permits is delivered to Brophy Water District (BWD), Browns Valley Irrigation District (BVID), Cordua Irrigation District (CID), Dry Creek Mutual Water Company (DCMWC), Hallwood Irrigation Company (HIC), Ramirez Water District (RWD), South Yuba Water District (SYWD) and Wheatland Water District (WWD). BVID receives water at the Pumpline Diversion Facility, located on the north-side of the river, approximately one mile upstream from Daguerre Point Dam. CID, HIC, and RWD receive water through the Hallwood-Cordua Canal (North Canal), located on the north abutment of Daguerre Point Dam. BWD, SYWD, DCMWC, and WWD receive water through the Yuba Main Canal Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-15

62 (South Canal), located on the south side of the Yuba River slightly upstream of the south abutment of Daguerre Point Dam Brophy Water District Since 1985, all water from the Yuba River used by BWD has been delivered through the South Canal under contract with YCWA. BWD s contract with YCWA provides for a Base Project Water allocation of 43,470 ac-ft and a Supplemental Water allocation of 32,177 ac-ft Browns Valley Irrigation District BVID holds a pre-1914 appropriative water right to divert up to 47.2 cfs of water year-round from the Yuba River for agricultural use. In addition, BVID holds post-1914 appropriative water rights on Dry Creek. These post-1914 appropriative rights allow for direct diversion and storage of water in Merle Collins Reservoir. BVID also has a contract with YCWA authorizing diversions of 9.5 TAF per year at its Pumpline diversion facility on the Yuba River to supplement BVID s diversions under its pre-1914 appropriative right when North Yuba River flows decrease below 47.2 cfs Cordua Irrigation District CID holds a pre-1914 appropriative right to divert up to 75 cfs from the Yuba River for agricultural use, and 1940 and 1948 appropriative rights to divert an additional 90 cfs. CID also has a contract with YCWA for 12 TAF of Base Project Water. CID diverts all of its Yuba River water from Daguerre Point Dam through the North Canal Dry Creek Mutual Water Company DCMWC receives all surface water deliveries from the South Canal under contract with YCWA. DCMWC began receiving water from YCWA in 1998; prior to 1998, the only water available to DCMWC was groundwater. DCMWC s contract with YCWA provides for a Base Project Water allocation of 13,682 ac-ft and a Supplemental Water allocation of 3,061 ac-ft Hallwood Irrigation Company HIC has a pre-1914 appropriative right to divert 150 cfs from the Yuba River, and a 1940 appropriative right to divert 100 cfs from the Yuba River. In a settlement agreement with YCWA regarding its water right, HIC agreed to receive a Base Project water allocation of 78 TAF per year from YCWA from the North Canal at Daguerre Point Dam Ramirez Water District RWD received water from CID from 1978 to Since 1992, RWD has received contract water from YCWA. RWD s contract with YCWA provides for a Base Project Water allocation of 14,790 ac-ft and a Supplemental Water allocation of 10,311 ac-ft. RWD receives water from the North Canal at Daguerre Point Dam. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

63 4.1.7 South Yuba Water District Areas of SYWD began receiving surface water from the South Canal in 1985 with an original contract amount of 33.9 TAF per year. Since 1992, SYWD has received all of its surface water deliveries from the South Canal under contract with YCWA. Since 1996, SYWD s contract with YCWA provides for a Base Project Water allocation of 25,487 ac-ft and a Supplemental Water allocation of 18,843 ac-ft Wheatland Water District WWD completed the Wheatland Project to deliver surface water to its farmers in The Wheatland Project was in two phases; the completed Phase 1 provides surface water to approximately 7,750 ac of the approximately 9,200 ac to be served upon completion of both phases. Under Phase 1, WWD s contract with YCWA provides for a total allocation (base and supplemental) of 23,092 ac-ft per year. The completion of Phase 2 will provide WWD with a total of 40,230 ac-ft per year. 4.2 Delivery Demands For modeling purposes, historical land use, applied water, and delivery patterns were analyzed to develop two basin-wide daily diversion demands; a wet year demand and a dry year demand. Annual demands for two levels of development, a present and a future condition, were developed; in the present level of development case, only lands irrigable by existing infrastructure are included. For the future level of development case, the full area of WWD is considered irrigated by Yuba River water, all other district demands remain the same. Table includes a summary of the synthetic annual delivery demands for each member unit, under present and future levels of development. Table Synthetic annual delivery demand for YCWA Member Units. Synthetic Annual Demand (ac-ft) YCWA Member Unit Present Level Development Future Level Development Key: ac-ft = acre-feet Wet Year Dry Year Wet Year Dry Year Brophy Water District 67,187 70,413 67,187 70,413 Browns Valley Irrigation District 34,723 36,383 34,723 36,383 Cordua Irrigation District 55,494 58,398 55,494 58,398 Dry Creek Mutual Water Company 15,552 16,034 15,552 16,034 Hallwood Irrigation Company 47,252 49,394 47,252 49,394 Ramirez Water District 24,295 25,596 24,295 25,596 South Yuba Water District 34,860 36,725 34,860 36,725 Wheatland Water District 11,835 12,139 31,651 32,667 Totals 291, , , ,610 Historical daily delivery patterns for 2003 through 2007 were evaluated to develop a wet and dry year delivery pattern which was then applied to the annual volumes developed using land use Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-17

64 and applied water rates. In simulation, daily deliveries are aggregated into a single daily value, and simulated at Daguerre Point Dam. 4.3 Diversion Shortage Provisions Because of the range of water rights and contract conditions, deficiency provisions vary by Member Unit. Base Project Water allocations are tied to unimpaired Yuba River flow at Smartsville, and Supplemental Water Supplies are tied to availability. Several Member Units have water rights in addition to their contracts with YCWA that are not subject to deficiencies except under extreme conditions. Specific contract deficiency provisions are shown in Table Table Yuba County Water Agency Water Supply Contracts Deficiency Provisions Category Unimpaired Runoff Forecast [a] Pre-1914 Rights Settlements: (a) CID, HIC Percentage of Settlement/ Contract Allocation Available f 40% 100% f < 40% 80% (b) BVID Forecasts All 100% YCWA Supply Contracts: (a) Base Supply 85% f 100% 50% f < 85% 85% 40% f < 50% 70% f < 40% 50% (b) Supplemental Supply All Forecasts Determined annually by YCWA in its reasonable discretion considering forecasted runoff and operational conditions. Note: [a]. April 1 DWR forecast of unimpaired Yuba River runoff near Smartsville, in percentage of 50-year average. 5.0 Model Overview The Model (YRDPM) simulates Project operations on a daily timestep for a user-designated period of record. Using historical hydrology, the YRDPM simulates user-defined operations using a consistent set of operational and physical constraints to determine the project s response to a wide range of hydrology. Since the YRDPM is simulating historical hydrology against physical and regulatory conditions that did not necessarily exist at any given time in project history, a direct long-term comparison of model output against historical conditions would not be practical and could be very misleading. A Validation Scenario was developed using historical regulatory conditions to test the YRDPM s performance in simulating historical conditions, but other than for the Validation Scenario, the model output should not be compared to historical conditions. The Validation Scenario is documented in Delivery Demand Development Report. Comparison of the model output from simulations with different physical or regulatory conditions can, however, lead to an understanding of a potential range of effects associated with specific physical or regulatory changes. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

65 5.1 Platform Selection Based on experiences with several other recent FERC Relicensing proceedings, several model platforms were evaluated before a specific tool was selected. Evaluated models included the following: USACE HEC-ResSim RiverWare Water Evaluation and Planning (WEAP) model Microsoft Excel-Based Model A comparison of the various platforms evaluated each platform s performance against a wide range of criteria. Each criterion was assigned a relevance level (low-medium-high), and each model was evaluated against the criteria using a scale of 1 to 5, with 5 meaning the model fit the criteria perfectly, and 1 meaning the model did not meet the criteria at all. Model criteria included considerations for the interface, general hydrologic capabilities, hydropower generation-specific capabilities, water resource-specific capabilities, presentation and aesthetics, cost and support, and experience and acceptance. Based on these criteria, the top scoring platforms were Microsoft Excel and HEC-ResSim. HEC-ResSim was initially selected as the modeling platform for the hydrologic modeling, largely based on its wide-spread acceptance and stake-holder familiarity from other FERC Relicensing projects. Initial model development using HEC ResSim indicated several fatal shortcomings in the model platform including the following: Modeling of the Project requires the ability to dynamically compute the North Yuba Index based on previous year s end-of-september storage and forecasted inflows. ResSim is not capable of this without extensive jython coding. Modeling of the Project requires the ability to reduce deliveries in order to meet an end-of- September carryover storage target in New Bullards Bar Reservoir. HEC-ResSim does not have the capability of iterating to meet an end-of-september target without extensive jython coding. Modeling of the Project requires the ability to apply instream flow requirements based on the North Yuba Index. ResSim does not have the capability of applying year-type dependant flow requirements without extensive jython coding. After discovering HEC-ResSim was incapable of accurately simulating operations of the Project in a manner consistent with YCWA specifications, a model based on Microsoft Excel was selected for hydrologic modeling of the project, largely due to its dynamic nature and userfriendly data management capabilities. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-19

66 5.2 Modeling Basics The YRDPM was developed in Microsoft Excel, with almost all of the logic and computations written in Visual Basic for Applications (VBA). The model uses Hydrologic Engineering Center Data Storage System (HEC-DSS) for input and output timeseries storage and management. Model development began in December 2008 and Version 1.0 of the model was made public in July Timestep The YRDPM utilizes a daily timestep for Project operations simulation. Some of the decisions are made using a weekly volume, as described below. The model has the capability of simulating time periods from as long as 41 years of hydrology (water years 1970 through 2010) to as short a time interval as a single day. All simulations must run through September 30. Internally, the model reads input and writes output to simulate as much as a single year at a time. Longer durations require subsequent internal iterations of reading input and writing output; however, from a user s perspective, multiple years and single years are managed in the same way. Flows in the Yuba River and its tributaries have been gaged by several agencies for varying lengths of time. Generally, a reliable mean daily flow record for major watershed streams exists from 1969 to the present day. Given the availability and reliability of these gaged flow data, flow measurements for the period of record (POR) of October 1969 through September 2008 were selected for inclusion in the compiled hydrologic data set for inflows to the Project area YRDPM Model Coverage The YRDPM model includes the following: The North Yuba River below Goodyears Bar Slate Creek above the Slate Creek Diversion Dam Canyon Creek at its confluence with the North Yuba River New Bullards Bar Dam and Reservoir The Middle Yuba River from immediately above Our House Dam Oregon Creek from immediately above Log Cabin Dam Our House Dam Log Cabin Dam The Lohman Ridge Tunnel The Camptonville Tunnel The South Yuba River below Jones Bar Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

67 Deer Creek near Smartsville New Colgate Powerhouse New Bullards Bar Dam New Bullards Bar Minimum Flow Hydro Englebright Dam and Reservoir Narrows 1 and 2 powerhouses Daguerre Point Dam YCWA agricultural demands Smartsville gage Marysville gage Yuba River from the confluence of the North and Middle Yuba rivers to the Feather River Figure shows the hydrologic schematic for the YRDPM. The model provides output for each of the reaches shown, and receives input flows at each of the arrows. See Hydrology Report for a detailed discussion of the input hydrology. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-21

68 Source: MWH Americas, Inc. Figure Reaches. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

69 5.2.3 Inputs YRDPM input is classified into two categories: hydrologic input and operations input Hydrologic Input Hydrologic input to the YRDPM is read as a timeseries from a DSS file. Table indicates the input description and its name in the input DSS file. As previously mentioned, all input timeseries contain daily records for the period of 10/1/1969 through 9/30/2010. Table YRDPM Hydrologic Input Data and DSS Names. Description Accretions from Canyon Creek Deer Creek Inflow Daguerre Point Agricultural Diversion Demand Dry Creek Inflow Total Accretions to Englebright Reservoir Accretions to the Englebright Reservoir Area Maximum daily pumping volume for groundwater substitution transfer Accretions to the Middle Yuba River below Oregon Creek Accretions to the Middle Yuba River above Oregon Creek Accretions to the North Yuba River below Goodyears Bar Accretions to Oregon Creek below Log Cabin Dam Accretions to Slate Creek below the Slate Creek Diversion Dam Accretions to the South Yuba River below Jones Bar Middle Yuba River Inflow above Our House Dam Total Accretions to New Bullards Bar Reservoir Accretions to the New Bullards Bar Reservoir Area North Yuba River Inflow above Goodyears Bar Oregon Creek Inflow above Log Cabin Dam Slate Creek Inflow above the Slate Creek Diversion Dam Slate Creek Inflow below the Slate Creek Diversion Dam South Yuba River Inflow at Jones Bar DSS Name CANYON_CR_ACC DEER_CR DGP_DEM DRY_CK EB_ACC_TOTAL ENG_RES_ACC GWS_MAX_PUMP LOWER_M-YUBA_LOW_ACC LOWER_M_YUBA_MID_ACC LOWER_N_YUBA_ACC LOWER_OREGON_CK_ACC LOWER_SLATE_CR_ACC LOWER_S_YUBA_ACC M_YUBA NBB_ACC_TOTAL NBB_RES_ACC N_YUBA OREGON_CK SLATE_CR SLATE_CR_BLW_DD S_YUBA Operations Input Many of the user inputs are not timeseries, and must be input by hand. Operations inputs fall into several categories. Those categories are as follows: Simulation Variables: Variable related to running the simulation such as starting date, initial conditions, and various on/off switches. Operational Parameters: Variables related to project operations not tied to a specific regulatory requirement or agreement such as carryover storage factors Regulatory Requirements and Agreements: Instream flow requirements and ramping constraints Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-23

70 Infrastructure/Capacity Inputs: Physical capacities and elevations of the various Project facilities Timeseries Inputs: Regulatory constraints imposed as timeseries Table lists operations user-inputs for the YRDPM. Table Operations Inputs for the YRDPM. Operations Input Start Date End Date Starting NBB Storage Starting Englebright Storage Use error checking? Use Automatic Calculations Throughout? Calculate Water Balance? Narrows 1 & 2 Flow Split Slate Creek Operations DSS Input File DSS Output File Simulation Name: Use Weekly Power Generation Factors? Ensure YCWA Receives Full North Yuba River Water Right? Meet all YCWA Water Rights Prior to Diversion? SFWP Flow Requirements Groundwater Substitution Transfers: GWS Pumping/Release Pattern Level of Development Target Operating Line Drought Level of Protection (for Carryover Storage) Maximum Carryover Storage Delivery Target (for Carryover Storage) Maximum Deficiency Maximum September & October Release Above Minimums Maximum New Colgate Release Reduction for Englebright Spill Avoidance Our House Dam Release Buffer Log Cabin Release Buffer Description Simulation Variables Initial date of simulation Final date of simulation Initial storage of New Bullards Bar Reservoir Initial storage of Englebright Reservoir Yes/No switch to select whether or not all error-checking will be used. Yes/No switch to select whether or not automatic calculation is used in each simulation step Yes/No switch to select whether or not the model does a water balance check at key locations for each time step Defines which method used to split Englebright releases between the Narrows 1 and 2 powerhouses Defines which method is used to determine Slate Creek flows below the Slate Creek Diversion Dam. Path and file name of DSS file containing hydrologic input timeseries data Path and file name of DSS file for the model to write output to. Can be either a new file or an existing one Name used as the F-Part when writing output to the DSS output file Yes/No switch to select whether or not weekly New Colgate generation is reshaped according to power generation factors Yes/No switch to specify whether YCWA s full water right for North Yuba River water is met prior to any SFWP diversions from Slate Creek. Yes/No switch to specify if SFWP can divert from Slate Creek if YCWA has met its water rights? If yes, then SFWP cannot divert from Slate Creek if YCWA is operating for minimum requirements on Yuba River unless North Yuba inflow exceeds YCWA water right amount. Defines if SFWP diversions and minimum flows are according to current rules, or their proposed FERC requirement. Yes/No switch to specify whether or not Groundwater Substitution Transfers will be included in the simulation Switch to identify source of pattern for groundwater pumping and transfer release: either using the default timeseries or using a pattern specified in the input DSS file. Operational Parameters Level of development for agricultural diversion demand New Bullards Bar Reservoir target operating line Exceedance probability of drought used to calculate minimum end-of-september New Bullards Bar Reservoir storage Greatest volume of computed minimum required end-of-september New Bullards Bar Reservoir storage Minimum allocation of agricultural deliveries for following year used to compute minimum required end-of-september New Bullards Bar Reservoir storage Maximum deficiency of agricultural deliveries before reducing instream flows Maximum allowable Englebright release above minimum required flow in September and October Maximum reduction in New Colgate releases to avoid spills from Englebright Reservoir due to high flows on the Middle and South Yuba rivers Used to add a buffer to required flow below Our House Dam Used to add a buffer to required flow below Log Cabin Dam Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

71 Table (continued) Operations Input New Bullards Bar Minimum Flow Hydro Release Buffer Flood Pool Buffer Target Englebright Storage Elevation Trigger for Max Narrows: Englebright Spill Avoidance Forecast Englebright Inflow Threshold (For Flow Fluctuation) Carryover Storage Operation Buffer Evaporation Instream Flow Requirements Hydrologic Index Starting Year Type Maximum Flow Below Dam: Maximum Flow in Marysville September 15 to October 31 Flow Reduction November 1 to March 31 Maximum Flow Reduction Maximum Daily Flow Reduction Englebright Minimum Pool Elevation Lohman Ridge Tunnel Capacity Camptonville Tunnel Capacity New Colgate Max New Bullards Bar Reservoir Maximum Storage New Bullards Bar Reservoir Normal Max Elevation FERC Minimum Pool Englebright Dam Crest Elevation Englebright Minimum Pool Elevation Englebright Area Narrows 1 Capacity Narrows 2 Capacity Narrows 2 Min Release New Colgate Turbine Elevation Operational Parameters (continued) Description Yuba County Water Agency Used to add a buffer to required flow below New Bullards Bar Dam Buffer on flood pool, used to determine if New Colgate releases can be reduced for Englebright spill avoidance. Ideal end-of-day Englebright Reservoir storage. If storage is below the Target Englebright Storage, New Bullards Bar Reservoir releases may be increased. If storage is above the Target Englebright Storage, New Bullards Bar Reservoir may be decreased. Englebright Reservoir water surface elevation which, if exceeded could result in maximum release through the Narrows powerhouses. Number of days forward the model will look at Englebright inflows to see if reductions in New Colgate releases is necessary to avoid spilling Englebright Dam Englebright inflow threshold above which flow fluctuation criteria will not be applied. Primarily used to identify flows in excess of base flow for fall and winter from which maximum reductions are determined. Volume of buffer above FERC Minimum Pool Assumed annual evaporation in TAF for purposes of determining carryover storage requirement. Regulatory Requirements and Agreements Controlling minimum instream flow requirements Hydrologic Index used for the Instream Flow Requirements The hydrologic year-type for the starting date Maximum release from New Bullards Bar Dam for flood management Maximum flow in Marysville for flood management Maximum allowable reduction of flows below Englebright between September 15 and October 31. From the Narrows 2 Bypass FERC Amendment Maximum allowable reduction of flows below Englebright between November 1 and March 31. From the Narrows 2 Bypass FERC Amendment Maximum daily reduction in flow below Englebright Reservoir for any time of the year. From the Narrows 2 Bypass FERC Amendment Minimum storage target for Englebright Reservoir, currently defined by PG&E agreement with Englebright marinas Infrastructure and Capacity Inputs Physical capacity of Lohman Ridge Tunnel Physical capacity of Camptonville Tunnel Maximum release capacity of New Colgate Powerhouse Maximum storage of New Bullards Bar Reservoir, including surcharge space Normal maximum water surface elevation in New Bullards Bar Reservoir New Bullards Bar Reservoir FERC minimum pool storage volume. Reservoir storage will not be drawn below this storage volume. Elevation of Englebright Dam crest. Water surface elevation in excess of this elevation will result in spill Minimum allowable water surface elevation in Englebright Reservoir. Assumed area of Englebright Reservoir at 40,000 ac-ft of storage Maximum release capacity of Narrows 1 Powerhouse Maximum release capacity of Narrows 2 Powerhouse Minimum release from Narrows 2 Powerhouse due to efficiency limitations. Narrows 2 Powerhouse will not release lower flow. Elevation of New Colgate Powerhouse turbines. Used to determine head differential and resulting generation Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-25

72 Table (continued) Operations Input Description Infrastructure and Capacity Inputs (continued) Assumed normal water surface elevation of Yuba River for both Narrows 1 and Narrows Tailwater Elevation: Narrows 2 powerhouses. Used to determine head differential and resulting generation YCWA North Yuba Water Right: YCWA s water right to North Yuba River flows Maximum cumulative volume of South Feather Water and Power diversions from Maximum SFWPA Diversion Volume (Jan-Jul): the Slate Creek Tunnel above 300 cfs between January and July per SFWPA s water right. Timeseries Inputs Daily average Yuba River flow requirement at Smartsville, as measured at the Flow Requirements at Smartsville Smartsville gage Flow Requirement at Marysville Target Operating Line Volume above Target Line Volume below Target Line Instream Flow Requirement Below Our House Dam Instream Flow Requirement Below Log Cabin Dam Evaporation Rate Instream Flow Below New Bullards Bar Dam Flow Requirement below Slate Creek Diversion Dam Power Generation Factor Settings Daily average Yuba River flow requirement at Marysville, measured at the Marysville gage Target storage in New Bullards Bar Reservoir. The model will make releases to reduce storage to this level, subject to an upper and lower buffer. Releases for target operating line are limited to non-spill releases. When New Bullards Bar Reservoir storage is between the Upper and Lower target lines, releases are linearly interpolated between maximum New Colgate capacity and releases for instream flow requirements. Added to Target Operating Line to define Upper Target Line. If New Bullards Bar Reservoir storage exceeds the Upper Target Line, releases will be made at full New Colgate Capacity Subtracted from Target Operating Line to define Lower Target Line. If New Bullards Bar Reservoir storage is less than the Lower Target Line, releases will be limited to meeting instream flow requirements. Required Middle Yuba River flow below Our House Dam. Currently defined by FERC License 2246 and 1965 YCWA-DFG Agreement (YCWA and CDFG 1965) Required Oregon Creek flow below Log Cabin Dam. Currently defined by FERC License 2246 and 1965 YCWA-DFG Agreement (YCWA and CDFG 1965) Monthly evaporation rate in inches for Englebright or New Bullards Bar Reservoirs. Release through the New Bullards Bar Minimum Flow Hydro powerhouse at the base of New Bullards Bar Dam to meets instream flow requirement. SFWPA monthly flow requirement on the Slate Creek below the Slate Creek Diversion Dam Used to redistribute New Colgate Powerhouse releases throughout a week to simulate weekly power generation operations Outputs In addition to outputting regulated flow and cumulative flow for each of the reaches in Figure 5.2-1, the YRDPM outputs storage, flow, elevation, and generation information for all project components. Table indicates the output description, and its name in a standard output DSS file. The table does not list the output for the reaches indicated in Table 5.2-1, those output are simply labeled according to their reach number (i.e. REACH_001 for Reach 1) with a DSS data type of either REG_FLOW for regulated flow or NAT_FLOW for natural flow, or for the model inflows, which are labeled according to their input file name (INF_CANYONCR_ACC for Canyon Creek accretions). Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

73 Table YRDPM Output and DSS Names. Description DSS Name DSS Data Type Flow Through the Camptonville Tunnel CAMPTONVILLE_TUNNEL FLOW Flow Through the New Colgate Powerhouse COLGATE_FLOW FLOW Generation from the New Colgate Powerhouse COLGATE_GEN POWER Agricultural Delivery Allocation DGP_ALLOC SHORTAGE Agricultural Diversion Demand DGP_DEM FLOW Agricultural Diversion DGP_DIV FLOW End-of-Day Water Surface Elevation of Englebright Reservoir ENG_ELEVATION ELEVATION Evaporation from Englebright Reservoir ENG_EVAP EVAPORATION Inflows to Englebright Reservoir other than releases from New Bullards Bar Reservoir ENG_INFLOW_TOTAL FLOW Operation flags providing insight into what is controlling Englebright Reservoir operations ENG_OPFLAG FLAG Total Releases from Englebright Dam ENG_RELEASE FLOW Spills from Englebright Reservoir ENG_SPILL FLOW Englebright Reservoir End-of-Day Storage ENG_STORAGE STORAGE Water Balance Check around Englebright Reservoir ENG_WBAL SUM New Bullards Bar Reservoir New Bullards Bar Minimum Flow Hydro Release FISH_HYDRO FLOW Groundwater pumping flow to support groundwater substitution transfers. Corresponds with a decrease in Daguerre Point Dam GWS_PUMPING FLOW diversions Release of groundwater substitution transfer flow from New Bullards Bar Reservoir. Corresponds with an increase in flow at GWS_RELEASE FLOW the Marysville gage Minimum Instream Flow Requirement below Log Cabin Dam LOG_CABIN_MIF FLOW Releases to Oregon Creek from Log Cabin Dam LOG_CABIN_RELEASE FLOW Flow in the Lohman Ridge Tunnel LOMANRIDGE_TUNNEL FLOW Yuba River Flow at the Marysville Gage MRY_FLOW FLOW Minimum Instream Flow Requirement at the Marysville Gage MRY_MIF FLOW Water Balance Check at the Marysville Gage MRY_WBAL SUM Release through the Narrows 1 Powerhouse NARROWS1_FLOW FLOW Generation at the Narrows 1 Powerhouse NARROWS1_GEN POWER Release through the Narrows 2 Powerhouse NARROWS2_FLOW FLOW Generation at the Narrows 2 Powerhouse NARROWS2_GEN POWER Bypass flow at either of the Narrows powerhouses; non-spill or generating flow NARROWS_BYPASS FLOW Flag indicating what is driving the flow split between the Narrows 1 and 2 powerhouses NARROWS_FLAG FLAG Combined flow through the Narrows 1 and 2 powerhouses NARROWS_FLOW FLOW Combined generation at the Narrows 1 and 2 powerhouses NARROWS_GEN POWER End-of-Day Water Surface Elevation of New Bullards Bar Reservoir NBB_ELEVATION ELEVATION Evaporation from New Bullards Bar Reservoir NBB_EVAP EVAPORATION End-of-Day Storage of the New Bullards Bar Reservoir Flood Pool NBB_FLOOD_POOL STORAGE Total daily inflow into New Bullards Bar Reservoir NBB_INFLOW_TOTAL FLOW Lower End-of-Day New Bullards Bar Reservoir Operating Line NBB_LOWERTARGET_LINE STORAGE Total Daily Release from New Bullards Bar Reservoir NBB_RELEASE FLOW Spill from New Bullards Bar Reservoir NBB_SPILL FLOW End-of-Day New Bullards Bar Storage NBB_STORAGE STORAGE Upper End-of-Day New Bullards Bar Reservoir Operating Line NBB_UPPERTARGET_LINE STORAGE Water Balance Check at New Bullards Bar Reservoir NBB_WBAL SUM North Yuba Index Value NYI INDEX North Yuba Index Year-Type NYI YEARTYPE Required Minimum Instream Middle Yuba River Flow Below Our House Dam OUR_HOUSE_MIF FLOW Release to the Middle Yuba River from Our House Dam OUR_HOUSE_RELEASE FLOW Slate Creek flow below the Slate Creek Diversion Dam SLATE_CREEK FLOW Yuba River Flow at Smartsville SMV_FLOW FLOW Required Minimum Instream Yuba River Flow at Smartsville SMV_MIF FLOW Yuba River Index Value YRI INDEX Yuba River Index Year-Type YRI YEARTYPE Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-27

74 5.3 Incorporation of Changes in Upstream Project Operations With pending FERC relicensing programs ongoing on Slate Creek, the Middle Yuba River, and the South Yuba River, changes in hydrologic operations on those tributaries are likely. These facilities have operated on a continuous and consistent basis for the entire YRDP POR. Due to these consistent historical operations, historical inflow hydrology to the YRDP accurately represents the affects of upstream project operations under current conditions. However, each upstream project is currently undergoing relicensing, which could result in operational/release changes due to new license conditions. Either revised reservoir operation rules or new minimum flow requirements could change the timing or volume of inflows to the Project. To include effects of any change in future upstream operation in Project model simulations, the Licensee proposes to use a method that applies resulting changes in flow due to upstream project operational changes to the historical inflow time series at corresponding gage locations. The YRDPM includes a Delta term on those three tributaries to be used for sensitivity studies assessing effects of changes in upstream operations on YRDPM inflows. Each upstream system has been modeled and base case and alternative simulations have been run for these projects. The change or difference in flow between the base case and the alternative scenario for the project of concern will be applied to the appropriate Project historical inflow time series to include effects of upstream project operational changes on Project hydrology. Since the upper basin and Project periods of record may be different, the shortest available POR is used for analysis. Through this methodology, all changes in upstream project operations can be incorporated as a sensitivity study and a part of any Project evaluation. 6.0 Characterization of Physical Facilities The model simulates operations of the Project by routing inflows to New Bullards Bar Reservoir, Our House Dam, Log Cabin Dam, Englebright Reservoir and the Yuba River through the various facilities and features in the Project Area. Inflows to Our House Dam on the Middle Yuba River are routed either to the lower Middle Yuba River, to ensure compliance with a flow requirement on the Middle Yuba River below Our House Dam, or into the Lohman Ridge Tunnel, flowing to Oregon Creek. There, the flow from the Lohman Ridge Tunnel is combined with Oregon Creek inflow to be released at Log Cabin Dam to either lower Oregon Creek, to ensure compliance with a flow requirement for the Oregon Creek below Log Cabin Dam, or into the Camptonville Tunnel. The Camptonville Tunnel flows are released into New Bullards Bar Reservoir, and releases to lower Oregon Creek combine with Middle Yuba River flows and area accretions to flow into the Yuba River. On the North Yuba River, inflows above Goodyears Bar combine with Slate Creek inflows and area accretions to flow into New Bullards Bar Reservoir. All inflows to New Bullards Bar Reservoir are either stored or released to the North Yuba River or Yuba River below the Dam; a portion of the New Bullards Bar Reservoir releases are made to the North Yuba River to ensure compliance with a requirement on the North Yuba River below New Bullards Bar Reservoir, the remainders are released several miles downstream from New Colgate Powerhouse to the Yuba Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

75 River. Releases to the North Yuba River combine with flows from the Middle Yuba River to form the headwaters of the Yuba River. Several miles downstream of the confluence of the North and Middle Yuba rivers, Yuba River flows combine with releases from New Colgate Powerhouse to flow into Englebright Reservoir where they are combined with inflow from the South Yuba River and from local accretions. Releases to the Yuba River from Englebright Reservoir are made through either PG&E s Narrows 1 Powerhouse, YCWA s Narrows 2 Powerhouse, or as spill. USGS s Smartsville gage (USGS ), located on the Yuba River below Englebright Dam, is an important compliance location, both the Lower Yuba River Accord (Yuba Accord) (SWRCB 2008) and the SWRCB Revised Decision 1644 (RD-1644) (SWRCB 2003) include minimum instream flows at the gage. Flows at the Smartsville gage combine with flows from Deer Creek and Dry Creek before flowing through the Yuba Goldfields to Daguerre Point Dam, the site for YCWA agricultural diversions. USGS s Marysville gage (USGS ), located approximately five mi below Daguerre Point Dam, is the other key compliance location for the Yuba Accord and RD The Yuba River meets the Feather River in the City of Marysville, six mi downstream of the Marysville gage. 6.1 Our House Dam and Lohman Ridge Tunnel Middle Yuba River inflows are introduced to the model above Our House Dam. Our House Dam splits Middle Yuba River inflows to two paths: the Lohman Ridge Tunnel or the Middle Yuba River below Our House Dam. The Lohman Ridge Tunnel releases into Oregon Creek above Log Cabin Dam, the Middle Yuba River joins with the North Yuba River to form the Yuba River. The maximum flow in the Lohman Ridge Tunnel is assumed to be 850 cfs, there is no limitation on flows below Our House Dam. 6.2 Log Cabin Dam and Camptonville Tunnel Oregon Creek inflows are introduced to the model above Log Cabin Dam. Log Cabin Dam also receives flows from the Lohman Ridge Tunnel. Inflows to Log Cabin Dam are split to either the Camptonville Tunnel, which flows into New Bullards Bar Reservoir, or to Oregon Creek, which later joins the Middle Yuba River below Our House Dam. The maximum flow capacity of the Camptonville Tunnel is assumed to be 1,100 cfs, there is no maximum release from Log Cabin Dam to Oregon Creek. 6.3 Slate Creek Diversion Dam Inflows from Slate Creek to the Slate Creek Diversion Dam are subject to diversion to the South Feather River via the Slate Creek Tunnel. The model has two modes of simulating Slate Creek inflows to the Project, the model can use either the timeseries of historical inflows below the Slate Creek Diversion Dam; or inflows above the Slate Creek Diversion Dam that are diverted according to SFWPA and YCWA water rights. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-29

76 Using the Historical Flows option, Slate Creek flows below the Slate Creek Diversion Dam at USGS gage are used as the inflow to the model. These inflows are added to synthetic accretions to represent inflows to the North Yuba River. Using the Slate Creek Only option, historical Slate Creek flow above the Slate Creek Diversion Dam are determined by adding USGS gage (Slate Creek below the Slate Creek Diversion Dam) and USGS gage (Slate Creek Tunnel below the Slate Creek Diversion Dam). The diversion amount is determined, subject to SFWP and YCWA s water rights and FERC licenses; and the maximum capacity of the Slate Creek Tunnel of 600 cfs. 6.4 New Bullards Bar Reservoir Simulation of New Bullards Bar Reservoir includes an elevation-storage-surface area curve defining reservoir storage and surface area for elevations ranging from 1,600 feet ft-msl to 1,965 ft-msl. Simulated inflows to New Bullards Bar come from the following: The North Yuba River Accretions to New Bullards Bar Reservoir The Camptonville Tunnel Reservoir Releases Releases from New Bullards Bar Reservoir are made through one or more of the following outlets: New Colgate Powerhouse New Bullards Bar Minimum Flow Hydro New Bullards Bar Spillway Decisions about which outlet to use are made based on reservoir storage volume relative to several operation curves described later in this report. The New Colgate Powerhouse has a maximum release capacity of 3,430 cfs, the New Bullards Bar Minimum Flow Hydro has a maximum capacity of 6 cfs, and the spillway releases are governed by a curve relating water surface elevation to maximum release, shown in Table Table New Bullards Bar Reservoir Maximum Release. Elevation (ft-msl) Maximum Spillway and Powerhouse Release (cfs) 1,730 3,430 1,902 3,430 1,905 5,000 1,910 9,000 1,915 16,000 1,920 25,000 1,925 35,000 Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

77 Table (continued) Yuba County Water Agency Elevation (ft-msl) Maximum Spillway and Powerhouse Release (cfs) 1,930 46,000 1,935 61,000 1,940 76,000 1,945 93,000 1, ,000 1, ,000 1, ,000 1, ,000 Source: USACE, New Bullards Bar Reservoir, Reservoir Regulation for Flood Control, June Key: cfs = cubic feet per second ft-msl=feet above mean sea level Power Generation The model calculates hydropower generation as a function of the releases through New Colgate Powerhouse and the water surface elevation of New Bullards Bar Reservoir. Actual load-flow and efficiency curves for the powerhouse were unavailable, so empirical head, flow, and power generation data were analyzed to create both load-flow curves and the methodology for calculation of turbine performance under changing reservoir pool elevation conditions. Observed mean daily water surface elevations for New Bullards Bar Reservoir were available for the full POR of the Project, but to develop the best possible relationship, it was decided that hourly power generation and flow should be used; data for 2002 through 2008 was compiled and evaluated. For purposes of this evaluation, daily change in reservoir elevation is considered insignificant compared to the variability of hourly head and flow. While additional water years of data were available, it was desired to analyze a period with roughly consistent operations for the entire period of record, so hourly data from water years 2002 to 2008 for New Colgate Powerhouse was determined to provide a sufficiently large dataset. The gross head was calculated as the difference between the respective daily observed reservoir water surface elevation and the Pelton turbine centerline elevation at New Colgate Powerhouse. For calculation purposes, head was assumed to remain constant throughout the day. Microsoft Excel and HEC-DSS were used to organize and group the power generation, flow, and gross head data by date and respective hour. New Colgate hourly powerhouse generation was calculated as the combined generation of the both units. Efficiency was calculated for each hour by solving for efficiency in the power equation, as described below. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-31

78 Where: P = Power generation (kw) Q = flow through the system (cfs) H = Gross head through the system (ft) η = Total system efficiency The efficiency is the percentage of the measured power generation to the maximum power that could be generated with 100 percent component efficiencies and zero head losses within the conveyance system. For this study, the maximum efficiency is a function of the total gross head, making this the total system efficiency, not the powerhouse or turbine unit efficiency. By using the overall system efficiency, estimations components and conveyance headlosses were not calculated. System efficiencies are provided as check and discussion points, but were not incorporated into the model directly. Large portions of missing data for head or flow were observed within the dataset, making those hourly points unusable for analysis. Extreme outliers, or points outside of the powerhouse operating limits, were observed and were also removed from the dataset. This included hourly data with efficiencies of less than 20 percent or greater than 120 percent and New Colgate Powerhouse flows less than 100 cfs or greater than 3,500 cfs. Flows greater than 1,500 cfs with efficiencies less than 50 percent were also removed. The resulting filtered dataset had over 54,000 hours of measured generation, flow, and gross head data for New Colgate. Affinity laws, also referred to as similarity rules or laws, express the mathematical relationship between many of the physical, hydraulic, and operational parameters of geometrically similar (homologous) pumps and turbines (Arndt and Gulliver 1991). These laws are a set of equations and assumptions derived from fluid mechanics and hydraulics principles used to estimate performance of a pump or turbine in comparison to other homologous pumps or turbines (Zipparro and Hasen 1993). These rules are most often used in physical modeling or system sizing. For this analysis, the equations were adapted to evaluate performance of a single turbine under different operating conditions. With any known operating point for any pump or turbine, the affinity laws can be modified algebraically into the following equations that estimate the power and flow to a new head with the same efficiency as the original known operating point (Brown 1965). Adjustment for power generation at new head (Brown 1965): Adjustment for flow at new head (Brown 1965): Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

79 Where: P 1 = Known power generation at known head (MW) P 2 = Adjusted power generation under new head (MW) H 1 = known head (ft) H 2 = New head (ft) Q 1 = Known flow at known head (cfs) Q 2 = Adjusted flow at new head (cfs) Yuba County Water Agency Load-flow curves are based on a set static head. The above equations adjust power and flow from any single point on the load-flow curve based on changes in head with no loss in efficiency. In order to create new load-flow curves for New Colgate Powerhouse, this process was performed in reverse. The empirical power generation and flow values were adjusted based on the affinity equations to a new reference head. The resulting dataset of adjusted flow and power generation represent points on the new load-flow curve at the gross normal head of 1,390 ft for New Colgate Powerhouse. The extremely large dataset of over 54,000 points was difficult to manage and analyze, so power generation and flow data were averaged into 10 cfs incremental ranges, from the lowest operational flow to the maximum powerhouse or tunnel rated flow. This reduced the number of points within the dataset to less than 400 while maintaining acceptable data resolution. This became the working dataset for the steps outlined below. After plotting this averaged load-flow curve, it was observed that were still data inconsistencies that needed to be addressed, specifically local maximum points on the load-flow curve. In a hydropower facility, power generation increases with an increase in flow within normal operating limits. Local maximums that do not conform to these general principles prove problematic for modeling and optimization. In order to remove these inconsistencies, a data smoothing technique using a gausian (bell curve) weighting method was applied to create a weighted average for the values of the power generation values. This method applies a weighted average using the averaged power generation corresponding to 20 data points, or 200 cfs, above and below each point. The weights vary between one (at the hourly power generation data being analyzed) to near zero (at the upper and lower limits). The analyzed data point and those data points immediately adjacent to it have the greatest values. The weights then depreciate significantly before becoming near zero at the upper and lower limits. The Gaussian smoothing technique better represents the empirical generation and flow data than any linear, logarithmic, or polynomial regression for the entire curve, but does not function accurately within 200 cfs of the end of the lower and upper flow limits. A linear regression was performed on the lower 300 cfs at each facility and the results were used to calculate the power generation at the lower 200 cfs of the flow limit at the New Colgate Powerhouse. For the upper flow limits, a quadratic function was fit to the upper 400 cfs for the New Colgate facility. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-33

80 The final load flow curves are the combination of the Gaussian smoothing technique results and the calculated regressions at the upper and lower 200 cfs of flow. Using this revised load-flow curve, efficiencies were calculated using the power equation described above and an efficiencyflow curve was created for each facility. The New Colgate Load-Flow and Efficiencies curves are in Figures and below. Figure New Colgate Powerhouse Load-Flow Curve at Gross Head 1,396 ft. Figure New Colgate Efficiency Curve at Gross Head 1,396 ft. The flow-efficiency curves are also typical of efficiency curves for Pelton turbines. The efficiency curve for the Pelton turbines at New Colgate has a much higher efficiency over a broader range of operating conditions than the Francis turbine at Narrows 2. This is inherent to the six-jet Pelton turbine design, allowing operators to run each turbine with any number of jets Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

81 to maximize efficiency. For the New Colgate powerhouse, running two six-jet Pelton units, operations could range from one jet operating at minimum flows to all six jets in both units operating at the maximum rated discharge. Each combination of jets will have its own associated efficiency curve if allowed to operate under a full range of conditions. As the flow increases or decreases, the number of jets in operation is changed to maximize the efficiency and power production. Changing the number of jets in operation results in the efficiency curve, Figure 6.4-2, having noticeable humps in efficiency. The ability of the six-jet Pelton turbine to maintain a high, relatively steady efficiency curve results in a near linear load-flow curve. The diminishing increase in power production as the flow approaches the upper limits of discharge is attributed to the combined dip in the turbine efficiency curve and the affects of frictional head loss within the conveyance system. Head loss is a function of the flow velocity squared and becomes more pronounced when flows approach capacity. Generation is not computed for the New Bullards Bar Minimum Flow Hydro Evaporation Evaporation from New Bullards Bar Reservoir is assumed to follow a monthly pattern, as shown in Table YRDPM looks up New Bullards Bar Reservoir s surface area based on the reservoir s storage, and multiplies it by the daily evaporation rate to compute an evaporation volume. Table New Bullards Bar Reservoir Monthly Evaporation Factors. Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Monthly Evaporation Rate (in) Daily Evaporation Rate (ft) Source: Yuba River Basin Water-Power Operations Model Program Manual Key: in = inches ft = feet 6.5 Englebright Reservoir Simulation of Englebright Reservoir includes a stage-storage curve defined for 0.01-ft water surface elevation increments between 500 ft-msl and 550 ft-msl. Simulated inflows come from the Yuba River, the South Yuba River and local accretions Reservoir Releases Releases are made through either PG&E s Narrows 1 Powerhouse; YCWA s Narrows 2 Powerhouse; the powerhouse bypasses, which are aggregated for purposes of modeling; or as spill over the dam crest. Spills over the dam crest are uncontrolled and are a function of Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-35

82 reservoir water surface elevation. Table shows the maximum release from Englebright Reservoir, as a function of water surface elevation. Table Maximum Englebright Reservoir Release by Elevation. Source: Yuba County Water Agency Key: ft-msl = feet above mean-sea level cfs=cubic feet per second Water Surface Elevation (ft-msl) Maximum Release (cfs) , , , , , , , , , , ,000 Englebright Reservoir s range of operable water surface elevations is 516 ft-msl to 527 ft-msl. When water surface levels in Englebright Reservoir reach 516 ft-msl, the launch ramps at the Skipper s Cove Marina become unusable, and Englebright Dam s spillway crest is at 527 ft-msl. Releases through the Narrows 1 Powerhouse are limited to a maximum of 730 cfs; and releases through the Narrows 2 Powerhouse are limited to 3,400 cfs, for a maximum generating flow of 4,130 cfs. Due to efficiency limitations, Narrows 2 Powerhouse is not generally operated below 900 cfs, though it has recently operated as low as 700 cfs, if needed. Decisions about which powerhouse is used for releases are made based on the desired release rate, as described later in this report. Since there are no mechanisms to control flows over the dam crest, the YRDPM includes a curve relating water surface elevation over the dam crest to the rate of spill Power Generation When computing generation at the Narrows 1 or Narrows 2 powerhouses, reservoir water surface elevation and flow are used in conjunction with curves relating flow to powerhouse efficiencies. The equation for computing Narrows 1 generation in MW is as follows: -1.2+Flow^ *Flow*Head/11.815/1000 The calculation of Narrows 2 powerhouse generation is determined similarly to that of New Colgate Powerhouse: hourly empirical data for the period of 1995 through 2010 was evaluated to develop flow-head-efficiency relationships. Narrows 2 were removed under the following parameters: 1) flows of less than 600 cfs 2) flows greater than 3,600 cfs; or 3) flows greater than 1,500 cfs with efficiencies less than 50%. Additional Narrows 2 Powerhouse data points were removed when the sum of the Englebright Dam and spillway releases were greater than 5,000 cfs Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

83 in order to minimize the uncertainty related to tailwater affects. The final dataset included over 100,000 points, so Gaussian smoothing similar to that used for the New Colgate Powerhouse was also used. The Narrows 2 Load-Flow and Efficiencies curves are below in Figures and 6.5-2, respectively. In general, the Narrows 2 Powerhouse has the typical efficiency curve associated with a single Francis Turbine. The efficiency curve is characterized by a single maximum efficiency point and a steadier decrease in efficiency as one operates at flows further from the maximum efficiency point compared to the Pelton turbine. There is a noticeable dip in efficiency curve between 1,500 cfs and 1,900 cfs. Figure Narrows 2 Powerhouse Load-Flow Curve at Gross Head 240 ft. Figure Narrows 2 Efficiency Curve at Gross Head 240 ft Reservoir Evaporation Similar to New Bullards Bar Reservoir, simulation of Englebright Reservoir includes evaporation. Since there is little variation in Englebright Reservoir water surface area, Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-37

84 evaporation varies only by month; it is not dependent upon reservoir storage. Table shows the monthly Englebright Reservoir evaporation factors. Table Englebright Reservoir Monthly Evaporation Factors. Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Monthly Evaporation Rate (in) Daily Evaporation Rate (ft) Source: Yuba River Basin Water-Power Operations Model Program Manual Key: in = inches ft=feet 7.0 Characterization of Operational Rules As a deterministic model, the YRDPM must prescribe specific actions for all observed and anticipated conditions. Much of this logic is handled through VBA scripting, while other portions are managed through Excel formulas. This section provides a narrative description of the general operational logic for each facility. Operations specific to the Base Case are described in the Base Case section. 7.1 Our House Dam Operations As described above, Our House Dam makes releases through a valve near its base to meet instream flow requirements in the Middle Yuba River below Our House Dam, diverts additional flows into the Lohman Ridge Tunnel and spills any additional flows over the dam to the Middle Yuba River Instream Flow Requirements YCWA operates to meet a minimum flow, or all natural inflow up to the minimum flow, in the Middle Yuba River below Our House Dam. These requirements are currently defined in the Project s FERC requirements, and vary by date. For each day of simulation, the YRDPM determines the appropriate flow requirement, and releases either the natural inflow or the minimum flow, whichever is less, to the Middle Yuba River. In the case that releases are made to meet the minimum flow, a buffer flow is added, if available, to emulate real-world operations ensuring sufficient flow reaches the gage Diversions Once minimum flows have been met, inflows to Our House Dam up to the tunnel capacity are diverted through the Lohman Ridge Tunnel to Oregon Creek. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

85 7.2 Log Cabin Dam Operations As previously described, Log Cabin Dam makes releases through a valve at its base to meet instream flow requirements in Oregon Creek below Log Cabin Dam, diverts additional flows into the Camptonville Tunnel, and spills any additional flows over the dam to Oregon Creek Instream Flow Requirements YCWA s current FERC license requires a minimum flow, or all natural inflow plus diversions from Our House Dam (up to the minimum flow) be released to Oregon Creek from Log Cabin Dam. The required flow rate is dependent on the date. For each day of simulation, the YRDPM determines the appropriate flow requirement, and releases either the natural inflow or the minimum flow, whichever is less, to Oregon Creek. In the case that releases are made to meet the minimum flow, a buffer flow is added, if available, to emulate real-world operations ensuring sufficient flow reaches the gage Diversions Once minimum flows have been met, inflows to Log Cabin Dam up to the tunnel capacity of 1,100 cfs are diverted through the Camptonville Tunnel to New Bullards Bar Reservoir. 7.3 Slate Creek Diversion Dam Operations There are two available operational modes for the Slate Creek Diversion Dam. The purpose of each operational mode is to determine how much flow from Slate Creek is released to the YRDP as opposed to diverted to the SFP Historical Flows Under the Historical Flows mode, the timeseries of historical flows below the Slate Creek Diversion Dam is input to the model as an inflow to the YRDP. In this case, the YRDPM does not simulate any diversions to the Slate Creek Tunnel: the Slate Creek Diversion Dam is not a part of the simulation. Using this mode also necessitates the use of the change term described in Section 6.3: Slate Creek Diversion Dam, in case of changes in South Feather Project (SFP) operations. Also, this mode would reflect any changes in Slate Creek Diversion Dam operations over the past thirty years, so it is possible there are issues with consistency of the data over the POR. Since the YRDPM is intended to be used in a comparative mode rather than a predictive one, inconsistencies in upstream operations would not necessarily be a problem, however, since a change term will be used to represent new operations in the SFP inconsistencies in upstream operations, the other two simulation modes were added to avoid any perceived problems Slate Creek Only Under the Slate Creek Only mode, YCWA s and SFWPA s water rights and the SFP FERC License are used to make decisions about releases to Slate Creek and diversions to the Slate Creek Tunnel. Historical inflows to the Slate Creek Diversion Dam are allocated based on Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-39

86 meeting minimum instream flow requirements on Slate Creek, and by limiting SFWPA to its water rights for diversions. The model limits SFWPA to a diversion of 300 cfs year around, with an additional 300 cfs between January 1 and July 1, so long as the total volume flow above the initial 300 cfs is less than 35,000 ac-ft. The Slate Creek Only option includes two additional Yes/No switches. For the first, Ensure YCWA Receives Full North Yuba River Water Right? the first 800 cfs of flow on the North Yuba River above New Bullards Bar Dam must be available to YCWA; if New Bullards Bar Reservoir inflows are less than 800 cfs, SFWPA cannot divert at the Slate Creek Diversion Dam. The second switch, Meet All YCWA Water Rights Prior to Diversion? further limits SFWPA diversions by precluding SFWPA diversions when YCWA is operating to meet instream flow requirements on the Yuba River. 7.4 New Bullards Bar Reservoir Operations As the primary water supply reservoir in the YRDP, New Bullards Bar Reservoir operations are complex and affected by a range of constraints, both within the reservoir, and downstream of New Bullards Bar Dam. The YRDPM computes required releases, and then distributes those releases to the various outlets. Included in the simulation are the New Colgate Powerhouse, the New Bullards Bar Minimum Flow Hydro, and the New Bullards Bar Dam spillway. The New Bullards Bar Minimum Flow Hydro releases a constant 6 cfs, any additional non-spill releases are made through the New Colgate Powerhouse. The spillway is only used during flood management operations, and only after all other release options have been fully used Flood Management New Bullards Bar Reservoir must be operated from September 16 to May 31 to comply with Part 208 Flood Control Regulations, New Bullards Bar Dam and Reservoir, North Yuba River, California, pursuant to Section 7 of the Flood Control Act of 1944 (58 Stat. 890). Under the contract between the United States and YCWA entered on May 9, 1966, YCWA agreed to reserve 170,000 ac-ft of storage space for flood management in New Bullards Bar Reservoir in accordance with rules and regulations enumerated in the Hydrology Report on Reservoir Regulation for Flood Control (USACE 1972). The seasonal flood storage space allocation schedule is presented in Table If simulated storage exceeds the end of month flood reservation storage, also shown in Table 7.4-1, the YRDPM will make maximum releases from New Bullards Bar Reservoir through the New Colgate Powerhouse and New Bullards Bar Reservoir spillway, subject to downstream flow limitations and spillway capacity, to reduce storage to the flood management line. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

87 Table New Bullards Bar Reservoir Flood Reservation Storage. Storage Allocation (TAF) End of Month Storage (TAF) Yuba County Water Agency Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Source: United States Army Corps of Engineers, New Bullards Bar Reservoir, Reservoir Regulation for Flood Control, June 1972 Key: TAF = Thousands of acre-feet The release rate is determined by adding the forecasted volume of the current day s inflow to the end of the previous day s storage. If the forecasted storage exceeds the flood reservation line, the volume above the line is compared to the various release mechanisms, and releases are made from the reservoir. The first block of water is assumed to be released through New Colgate Powerhouse up to its full capacity of 3,430 cfs. Any remaining volume of water is assumed released through the New Bullards Bar Reservoir Spillway and is subject to the maximum release rates shown in Table 6.4-1, New Bullards Bar Reservoir Maximum Release. If the forecasted storage volume would not require spillway releases to reach the flood reservation line, and assuming no spill would occur at Englebright Reservoir, all releases would be made through the New Colgate Powerhouse down to the Target Operating Line (TOL), described below in Section In addition to reservation of flood control space in New Bullards Bar Reservoir, the flood management regulations include rules governing ramping rates as well as target maximum flows in the Yuba River and the Feather River below the confluence with the Yuba River. New Bullards Bar Reservoir is operated for the following maximum flows: 50,000 cfs on the North Yuba River below New Bullards Bar Dam 120,000 cfs on the Yuba River at Marysville 300,000 cfs on the Feather River below the Yuba River 320,000 cfs on the Feather River below the Bear River YCWA also coordinates operations with PG&E s Narrows 1 Powerhouse at Englebright Dam to utilize storage in USACE s Englebright Reservoir to capture winter storm freshets and reduce storm flows on the Yuba River below Englebright Dam (YCWA and PG&E 1966). This operation is accomplished by evacuating storage space in USACE s Englebright Reservoir in anticipation of storm peak flows. At times when New Bullards Bar Reservoir is not threatening to encroach above the flood reservation line into the flood management pool, the YRDPM may modify New Bullards Bar Reservoir operations to avoid spilling Englebright Reservoir. These operations will be described in Section 7.5.2, Flood Management. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-41

88 7.4.2 Target Operating Line When hydrologic conditions are such that reservoir operations to meet minimum requirements would result in excessively high reservoir storage, New Bullards Bar Reservoir operations are governed by TOL. Similar to the Flood Management Line, the YRDPM makes releases based on the previous day s storage and forecasted current day inflows to meet the TOL. Unlike the Flood Management Line, the TOL is only a target, and as such, the YRDPM utilizes a buffer to mimic the actual operations of the Project within a desired proximity to the TOL versus the more variable release pattern that is associated with strictly operating to a TOL. The YRDPM only makes releases through the New Colgate Powerhouse and the New Bullards Bar Minimum Flow Hydro to achieve the TOL; as long as New Bullards Bar Reservoir storage does not exceed the flood management line, the New Bullards Bar Reservoir spillway is not used. The TOL and its buffers are determined through iteration to approximate historical operations, and through discussions with project operations planners. As previously mentioned, the TOL includes a buffer extending both above and below the TOL, as shown in Table If New Bullards Bar Reservoir storage is forecasted to be at or below the lower edge of the TOL buffer, New Bullards Bar Reservoir releases are determined based wholly on meeting minimum downstream requirements. If New Bullards Bar Reservoir storage is forecasted to be at or above the upper edge of the TOL buffer, New Bullards Bar Reservoir releases are made at the maximum New Colgate Powerhouse release rate not resulting in a spill at Englebright Reservoir. For forecasted storage between the two buffer lines, a linear interpolation between releases for minimum downstream requirements and maximum release is used as the New Bullards Bar Reservoir release rate. Table Example New Bullards Bar Reservoir Storage Target Operating Line and Buffers. Upper Target Operating Line Storage (TAF) Target Operating Line Storage (TAF) Lower Target Operating Line Storage (TAF) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Source: Model iterations and through consultation with YRDP operations planners Key: TAF = Thousands of acre-feet Carryover Storage To protect against multi-year droughts, YRDPM simulation of New Bullards Bar Reservoir includes a Carryover Storage target for the end of September each year. Reservoir carryover storage is used to make up the difference between the available surface water supply and system demands (diversion demands, instream flow requirements and system operational losses) under dry conditions. For modeling purposes, the determination of the yearly carryover storage requirement is based on several factors: the drought protection level (specified on the Scenario Builder and Control worksheet); Member Unit water demands; instream flow requirements; minimum percentage delivery during the next year (specified on the Scenario Builder and Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

89 Control worksheet); and forecasted flows. The drought protection level is designed to provide full instream flow requirements and a specified percentage of diversion demands during the following water year, if that water year were to have the specified return period. For modeling purposes, the delivery carryover storage requirement is calculated as: Carryover storage requirement = Annual diversion requirement for member units (with 50 percent deficiency) + Annual instream flow requirement + Annual storage operational buffer (0 TAF for wetter years 45 TAF for extremely dry years) + Annual evaporation (15 TAF) + Minimum pool (234 TAF) - Available water for the Yuba River below Englebright Dam during the following year, if it were to have a specified hydrological condition (assumed to be 1-in-100 driest year) The Annual Storage operational buffer is used for the required carryover storage for the most extreme critical dry years. This additional amount of storage for carryover of these very dry years is used to ensure that there will be enough water in storage to meet downstream demands through the fall, until winter runoff commences. Available water for the Yuba River below Englebright Dam during the following water year includes the calculation of a System operational loss that is related to hydrology. System operational losses are present because the Yuba River is not completely controlled by the existing facilities (e.g., inflows from Deer Creek and Dry Creek). The following two relationships have been developed based on model simulations. The development of system loss is focused on the simulation results for drier water years, when the carryover storage requirements affect the water supply available for deliveries. Water Available Annually for the Yuba River below Englebright Dam = (Annual total unimpaired flow of Yuba River Basin) (Annual total unimpaired flow of Yuba River Basin) System Operational Loss = *10-8 (Annual total unimpaired flow of Yuba River Basin) To simplify the demand and instream flow requirements in the calculation of the annual carryover storage requirement, the diversion and instream fishery flow requirements for the period from October to March used for the above calculation are the requirements for above normal water years, which results in smaller diversion requirements and higher instream fishery flow requirements. Before the new year type classification is determined, the operation should Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-43

90 follow the year type defined in the previous year; however, this refinement is not considered necessary for the precision of modeling. If simulated end-of-september (EOS) New Bullards Bar reservoir storage falls below the Carryover Storage target, Daguerre Point Dam diversions are reduced so that simulated EOS storage meets the Carryover Storage target and the New Bullards Bar Reservoir operations module is rerun. The YRDPM will iterate, modifying Daguerre Point Dam diversions, until the Carryover Storage target is met, as long as Daguerre Point Dam diversions do not drop to less than a specified percentage of demand (specified on the Scenario Builder and Control worksheet). The Carryover Storage target is typically computed to ensure the subsequent year will have enough storage to meet Yuba Accord schedule 6 flow requirements and 50 percent of Daguerre Point Dam demands, assuming the volume of inflows to New Bullards Bar Reservoir are greater than or equal to inflows corresponding to a 1 in 100 year drought (99% exceedance). For most years, this corresponded to an EOS target of 431 TAF; however, if the current year is the second or third year of a drought, the EOS target can be lower, depending on how much flow there was in the previous one or two years Inactive Pool New Bullards Bar Reservoir s inactive pool is specified in its initial FERC license as 234 TAF. If storage drops to the inactive pool, all inflows are released up to the applicable minimum flow requirement Englebright Storage The YRDPM operates New Bullards Bar Reservoir to maintain Englebright Reservoir within the range of elevations described in Section 6.5, Englebright Reservoir. Without any consideration for power generation or flood management, the YRDPM releases a sufficient volume of water from New Bullards Bar Reservoir storage to ensure the end-of-day storage is the same as the previous end-of-day storage. New Bullards Bar Reservoir operations include some consideration for flood management at Englebright Reservoir, as discussed in Section 7.5.2, Flood Management Power Generation Since power generation is a key aspect of YRDP operations, it is included in the YRDPM, but power generation is typically not a key driver for simulated operations. The YRDPM includes the ability to modify daily operations within a week to better simulate real-world operations. Prior to approximately 2002, New Colgate releases closely followed power price drivers; average weekday prices were typically higher than weekend prices, so weekend releases were generally restricted to a volume sufficient to keep Englebright Reservoir from dropping below its low elevation restriction. Since 2002, New Colgate release patterns have reflected the ancillary services market and do not reflect consistent weekly patterns. Since the YRDPM does not currently include hourly operations, participation in the ancillary services market is not included Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

91 in YRDPM operations, but the model does include the capability to reshape releases to simulate daily power generation operations. Through the Use Weekly Power Generation Factors? option on the Scenario Builder and Control worksheet, the user can skew the weekly power generation pattern; after computing the weekly release volume, the Power Generation Factors can be used to emphasize certain days over others. For example, if the weekly release volume were low enough, all New Colgate Powerhouse releases could be made in a single day. If the daily release volume exceeds New Colgate Powerhouse s release capacity, the YRDPM will distribute excess flows to whatever day has remaining capacity, effectively reducing the effect of the Weekly Power Generation Factors. To accommodate the Weekly Power Generation Factors, the YRDPM always simulates Monday through Sunday. This is particularly important to note at the transitions between water years; if the simulation period covers multiple years, it is likely the first year of simulation will extend to the first Sunday occurring on or after September 30. Similarly, subsequent simulation years will begin on the first Monday occurring on or after October 1. Exceptions to these two modifications include the first and last years of simulation; the first year will begin on the specified date, if that date is not a Monday, the Power Generation Factors are not applied to that week. Similarly, the last week of simulation will always end on the specified date; if that date is not a Sunday, no Power Generation Factors are applied. 7.5 Englebright Reservoir Operations While Englebright and New Bullards Bar reservoirs are operated conjunctively to meet downstream flow requirements and diversion demands, simulated Englebright Reservoir releases through the Narrows 1 and Narrows 2 powerhouses are operated to minimize daily fluctuations in Yuba River flows. Additionally, release decisions for downstream demands are made at Englebright Dam; New Bullards Bar Reservoir releases are generally used to maintain storage in Englebright Reservoir. Simulation of Englebright Reservoir includes an Operations Flag indicating the controlling operation of Englebright Reservoir. Table shows the Operations Flags at Englebright Reservoir. Table Englebright Reservoir Operations Flags. Operations Flag Description 1 Marysville Flow Control 2 Smartsville Flow Control 2.5 Narrows 1 FERC License Smartsville Control 3 NBB Upper Target Storage Control 4 NBB Lower Target Storage Control 4.5 Englebright Fall Flow limit constraining (limit flow above lower Yuba required flow) 5 NBB Spill Control 6 Eng Spill Avoidance Control (reduction in NBB releases) Eng inflows for the previous 4 days reflect a storm event (non-spill), with non-nbb inflows in excess of a 6.5 specified threshold. 7 NBB Release + ENG inflow exceeds Narrows Capacity (Non-Spill) fills available Eng storage 8 Eng Spill Control (Non-NBB Spill) Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-45

92 Table (continued). Operations Flag Description 9 Flow Fluctuation Control 10 Daily Flow Reduction Control 11 New Bullards Bar Reservoir minimum pool controls 0 Other Instream Flow Requirements Englebright Reservoir always makes releases to meet instream flow requirements at the Smartsville and Marysville gages, and irrigation diversions from Daguerre Point Dam. The minimum release from Englebright Reservoir is either the flow requirement at Smartsville gage, or the sum of the Marysville gage requirement and Daguerre Point Dam irrigation demands less inflows from Deer and Dry creeks, whichever is greater Additionally, Englebright releases are constrained by operations to follow the flow fluctuation requirements defined in the Narrows 2 Bypass FERC Amendment (FERC 2005). The YRDPM computes the maximum 5-day Englebright Reservoir non-spill release volume for the period of September 15-October 31, and ensures Englebright releases do not drop to less than 55% of the maximum 5-day average release. Between November 1 and March 31, the YRDPM computes the maximum 5-day average non-spill release and ensures Englebright Reservoir releases do not drop below 65% of this flow, or the flow established for September 15 through October Flood Management While Englebright Reservoir has no flood management requirements, YCWA operates New Bullards Bar Reservoir to avoid spilling Englebright Reservoir. If forecasts indicate a relatively small storm, or a freshet is coming, New Colgate Powerhouse releases are reduced by a userdefined percentage, creating space in Englebright Reservoir for increased runoff from the Middle and South Yuba rivers. To simulate spill avoidance operations at Englebright Reservoir, the YRDPM evaluates Englebright inflow from the South and Middle Yuba rivers and accretions each day for the four subsequent days against Narrows 1 and 2 release capacities. If there is insufficient capacity to release the daily inflows, the Operation Flag is set at 6, and New Colgate releases are reduced by a Colgate Spill Avoidance Factor normally set at 70%. By applying this reduction factor four days before a storm event would occur, provides time for Englebright Reservoir storage to be reduced, creating space to capture the storm and avoid spills at Englebright dam. In some situations, spills are unavoidable, in which case application of the spill avoidance factors would reduce the volume of spill. The YRDPM always checks to make sure all Narrows 1 and 2 powerhouse capacity is used prior to releasing any spills over Englebright Dam Power Generation Englebright Reservoir releases are set based on downstream demands in drier time of all years and most of the time in dryer years, in wetter years and the winter of most years, releases are Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

93 made at relatively constant rates that are determined by the amount of uncontrolled flow into Englebright Reservoir plus planned releases from New Bullards Bar Reservoir. Since the YRDPM operates on a daily timestep rather than an hourly one, most power generation-related operations are not a part of the YRDPM. However, limited power generation operations are included. As previously mentioned, Weekly Power Generation Factors are used to weight generation on certain weekdays over others. Since Englebright Reservoir is operated to maintain relatively consistent flows on the Yuba River below Englebright Dam, variations in power generating flows from New Colgate Powerhouse are reflected as changes in storage at Englebright Reservoir. As such, the YRDPM operates Englebright Reservoir to maintain storage within a defined, limited range. If Weekly Power Generation Factors are used, New Colgate Powerhouse releases are reduced at certain times and increased at others. The YRDPM will adjust New Colgate Powerhouse releases as necessary to begin and end each week at the same Englebright Reservoir storage level. After computing both New Bullards Bar and Englebright reservoirs storage and releases reflecting the Weekly Power Generation Factors, the YRDPM conducts a second check to make sure Englebright Reservoir storage does not drop below a low storage level; if the low storage level is violated, New Colgate Powerhouse releases are increased on that day and reduced on all of the others. Generating releases from Englebright Reservoir can be made through either the Narrows 1 or Narrows 2 powerhouses. The YRDPM has two simulation modes for splitting Englebright Reservoir releases into the two powerhouses: 1) Narrows 2 Preference; and 2) Narrows 1 Preference. Under the Narrows 2 Preference setting, all available Narrows 2 Powerhouse capacity (3,400 cfs) is used before releases are made through the Narrows 1 Powerhouse, up to the Narrows 1 Powerhouse s full capacity (730 cfs). Under the Narrows 1 Preference setting, the order is reversed, and all Narrows 1 Powerhouse capacity is used before any releases are made through the Narrows 2 Powerhouse. 7.6 Daguerre Point Dam Deliveries A timeseries of demands is used for simulation of deliveries from Daguerre Point Dam. Even though diversions occur from three distinct locations, for simulation purposes all agricultural diversions for YCWA member units are assumed to occur at Daguerre Point Dam and are aggregated into a single demand and delivery point. For a full discussion of the development of the Daguerre Point Dam diversion demands, see the Agricultural Demand Development Report. Under normal conditions, Englebright Reservoir operations release sufficient water to meet or exceed flow requirements at Smartsville, or for Marysville requirements plus Daguerre Point Dam diversions. Under relatively wet conditions, releases may be made from New Bullards Bar Reservoir to meet an EOS target storage; under these conditions, flows at Smartsville and Marysville will likely be in excess of the regulatory minimum, and full deliveries would be made at Daguerre Point Dam. Under extremely dry conditions, releases to meet minimum flow Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-47

94 requirements at Marysville and diversions to meet full demands at Daguerre Point Dam could result in New Bullards Bar Reservoir dropping below the EOS carryover storage requirement. The YRDPM meets the full diversion demand at Daguerre Point Dam if the resulting end-of- September carryover storage in New Bullards Bar Reservoir is above the delivery carryover storage required for the specified level of drought protection (normally 1 in 100 years). Delivery deficiencies of up to a specified amount are allowed by the model to maintain delivery Carryover Storage requirements. The YRDPM will reduce Daguerre Point Dam diversions by a volume equivalent to the difference between the simulated New Bullards Bar Reservoir storage and the Carryover Storage requirement and resimulate New Bullards Bar Reservoir operations. Any reductions in Daguerre Point Dam diversions are applied only to periods when the Marysville flow requirement is controlling Englebright Reservoir operations; if Smartsville requirements are controlling Englebright Reservoir releases, no reductions in delivery can be applied. The reduction in delivery, or shortage, is computed as a percentage and applied to diversions from April 1 through March 31. A limit on reduction in deliveries can be applied to avoid reducing deliveries below a specified level. If the specified deficiency is reached, New Bullards Bar Reservoir is drawn down below the Carryover Storage requirement, as necessary, to prevent deficiencies from exceeding the specified deficiency during that year. 7.7 Water Transfers Water transfers are an important component of Project operations. In the 23 years between 1987 and 2010, YCWA transferred water in 18 years, averaging about 90 TAF in each transfer year. Details of individual transfers are presented in Table Stored water transfers were made by YCWA from storage releases from New Bullards Bar Reservoir. Currently, under the Yuba Accord, stored water transfers are mostly contained within the releases to meet Accord flow schedules, or to meet the standard end of September storage in New Bullards Bar Reservoir. Groundwater substitution transfers are made by YCWA in coordination with its Member Units. Water transfers are discussed here due to the inclusion of the capability for transfer within the model. Table Yuba County Water Agency historical sales 1987 to Sacramento Valley Index 9 Water Year Type Groundwater- Substitution Transfer (ac-ft) Year Buyer Stored Water Transfer (ac-ft) 1987 Dry California Department of Water Resources 83, Critical California Department of Water Resources 135, Dry 1990 Critical 1991 Critical California Department of Water Resources 90, California Department of Water Resources for California Department of Fish and Game 110, City of Napa 7, East Bay Municipal Utility District 60, City of Napa 6, California Department of Water Resources 109, Tudor Mutual Water Company/Feather Water District 2, State Water Bank 99, ,840 State Water Bank - California Department of Fish and Game 28, City of Napa 7, Critical State Water Bank 30, Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

95 Table (continued) Sacramento Valley Index 9 Water Year Type Yuba County Water Agency Groundwater- Substitution Transfer (ac-ft) Year Buyer Stored Water Transfer (ac-ft) 1994 Critical California Department of Water Resources 26, Wet 2001 Dry 2002 Dry 2003 Above Normal 2004 Below Normal Bureau of Reclamation for Refuge Water 25, Sacramento Area Flood Control Agency for American River Fishery 48, Environmental Water Account 50, California Department of Water Resources 52,912 61,140 Environmental Water Account 79,742 55,248 California Department of Water Resources 22, Contra Costa Water District 5, Environmental Water Account 65, Contra Costa Water District 5, Environmental Water Account 100, California Department of Water Resources Above Normal Environmental Water Account 6, Wet Environmental Water Account 60, Dry Yuba Accord Water Purchase Participants 65,000 6,7, Critical Yuba Accord Water Purchase Participants 117,212 6,g 48, Dry Yuba Accord Water Purchase Participants 91,100 6,7 -- DWR Drought Water Bank 88, Below Normal Yuba Accord Water Purchase Participants 74,179 66,211 Total 1,636, ,247 Key: ac-ft = acre-feet CID = Cordua Irrigation District DWR = California Department of Water Resources BVID = Browns Valley Irrigation District EWA = Environmental Water Account SWRCB = State Water Resource Control Board 1 Sold but not delivered. 2 In 1991, BVID transferred an additional 5.5 TAF to the State Water Bank through conservation. 3 In 1992, BVID transferred an additional 5.5 TAF to the State Water Bank through conservation. 4 In 1997, the transfer included 5 TAF from BVID. 5 In 2001, BVID transferred an additional 4.5 TAF to DWR (stored water transfer) and 3.5 TAF to the EWA (groundwater substitution pumping). 6 In 2002, 2003, 2003, 2007, 2008, 2009, and 2010, BVID transferred an additional 3.1 TAF to SCVWD through conservation. 7 Transfers to the Yuba Accord Water Purchase Participants includes 60 TAF of stored water for the Environmental Water Account. 8 The 2007 transfer was under Yuba Accord Pilot Program. It also included 60 TAF of transfer to the EWA purchased in Sacramento Valley Index as defined in SWRCB RD In 2009, CID transferred an additional 8,322 ac-ft of groundwater substitution transfer to the DWR Drought Water Bank Stored Water Transfers Historically, individual one-year stored water transfers have occurred when the projected end-of- September storage in New Bullards Bar Reservoir is sufficient for YCWA to ensure 100 percent deliveries to Member Units in the following year under a drought event with a 1-in-100-year return period. In addition, for cross-sacramento-san Joaquin Delta (Delta) water transfers to service areas south of the Delta, the Delta must be in balanced water conditions 3 and available 3 Balanced water conditions are periods when it is agreed that releases from upstream reservoirs plus unregulated flows approximately equal the water supply needed to meet Sacramento Valley in-basin uses plus required Delta outflows and exports (Reclamation and DWR 1986). Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-49

96 conveyance capacity must exist at Banks or Jones pumping plants. Stored water transfers have typically occurred from July through September. More recently stored water transfers are accomplished through a complex accounting of the releases to meet the Yuba Accord flow schedules and the end of September New Bullards Bar Reservoir storage target, and only minor additional stored water transfers have occurred, and these are scheduled to maximize fishery benefits, typically in September to smooth out flows during the early spawning period Groundwater Substitution Transfers Groundwater substitution transfers are implemented through agreements between YCWA and its Member Units. Member Units forego parts of their surface water deliveries at Daguerre Point Dam; irrigation needs associated with the foregone surface water deliveries are met through additional groundwater pumping. Water not delivered at Daguerre Point Dam is temporarily stored in New Bullards Bar Reservoir, and subsequently released to meet transfer demand. Transfer water may also be pre-delivered from New Bullards Bar Reservoir, and replaced by groundwater substitution pumping later in the year. The monthly pattern of recent historical groundwater substitution pumping, as measured at transfer wells, is presented in Table Table Yuba County Water Agency historical groundwater substitution pumping (ac-ft). Member Unit Apr May Jun Jul Aug Sep Oct Nov Dec Total 2001 Pumping Volumes 1 Brophy Water District Browns Valley Irrigation District Cordua Irrigation District -- 1,606 2,887 2,935 2,965 1,293 2, ,000 Dry Creek Mutual Water 104 1,131 2,364 2,006 2, ,161 Hallwood Irrigation Company 492 1,879 2,075 2,618 2, , ,020 Ramirez Water District 712 2,228 2,627 2,229 2,057 1,373 2,149 2,102 1,532 17,009 South Yuba Water District ,758 2,955 3, ,037 Subtotal 1,398 9,602 12,909 12,983 9,967 5,229 6,463 2,102 1,532 62, Pumping Volumes 3 Brophy Water District 187 1,350 4,965 2, , ,292 Browns Valley Irrigation District ,897 Cordua Irrigation District ,927 3,912-2, ,059 Dry Creek Mutual Water ,971 1, ,876 Hallwood Irrigation Company ,884 2, ,382 Ramirez Water District ,345 2,926 1, , ,812 South Yuba Water District ,919 1, ,767 Subtotal - 4,017 6,438 23,316 10,364 6,021 5, , Pumping Volumes 4 Brophy Water District 719 1,877 3,226 2,915 2, ,825 Browns Valley Irrigation District ,236 Dry Creek Mutual Water 715 1,317 1,761 1,750 1, ,424 Hallwood Irrigation Company 366 1,551 2,561 2,401 2,785 1, ,321 Ramirez Water District 853 1,321 2,289 2,054 1,509 1,408 2, ,081 South Yuba Water District ,103 Subtotal 2,991 6,968 10,837 10,313 9,439 4,771 3,556 1,114-49,989 Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

97 Table (continued) Member Unit Apr May Jun Jul Aug Sep Oct Nov Dec Total 2009 Pumping Volumes 5 Brophy Water District ,283 8,131 8,289 2,461 2, ,957 Browns Valley Irrigation District ,224 1, , ,834 Cordua Irrigation District ,485 3,644 1, ,262 Dry Creek Mutual Water ,360 2,028 1,611 1, ,739 Hallwood Irrigation Company ,505 2,616 3,047 1,821 1, ,015 Ramirez Water District ,324 2,284 2,137 1,162 2, ,790 South Yuba Water District ,804 4,688 4,537 1,690 3, ,605 Wheatland Water District ,824 3,943 2,691 1,187 1, ,473 Subtotal - 2,189 17,324 28,329 26,889 11,163 13, , Pumping Volumes 6 Brophy Water District ,777 10,284 4,539 1, ,925 Browns Valley Irrigation District , ,057 Dry Creek Mutual Water ,797 2,000 1, ,740 Hallwood Irrigation Company ,465 2,748 1,603 1, ,018 Ramirez Water District ,009 1, ,552 South Yuba Water District ,807 5,135 2,173 1, ,209 Wheatland Water District ,130 3,717 1, ,660 Subtotal ,456 25,951 12,571 6, , Pumping 7 Monthly Volume (ac-ft) 2,991 9,157 28,161 61,098 62,279 28,505 23,776 1, ,825 Monthly Distribution (%) 1% 4% 13% 27% 28% 13% 11% 1% 0% 100% Base Case Distribution (%) 0% 5% 15% 30% 30% 5% 10% 5% 0% 100% Key: ac-ft = acre feet 1 Includes 1,085 ac-ft of excess groundwater pumping in Previously reported as 9,995 ac-ft of pumping in other reports. 3 Includes 1,826 ac-ft of excess groundwater pumping in Includes 1,114 ac-ft of excess groundwater pumping in Includes 2,513 ac-ft of excess groundwater pumping in Includes 2,050 ac-ft of excess groundwater pumping in are Yuba Accord groundwater substitution years. The start of groundwater substitution pumping is dictated by New Bullards Bar Reservoir operations. Water can be backed up in storage under base flow operations when releases from New Bullards Bar Dam are not controlled by minimum flow requirements at the Smartsville Gage. Groundwater substitution pumping ceases once the transfer volume has been achieved, or at the onset of flood control or storm runoff operations for New Bullards Bar Reservoir. The total groundwater substitution transfer capacity of YCWA Member Units is the groundwater volume that can be pumped to substitute for surface water deliveries forgone by willing participants using existing wells. A 2005 survey (YCWA and MWH unpublished data) estimated available pumping capacity for YCWA Member Units, not including WWD, at approximately 98 TAF. Of that volume, 77.5 TAF is from electric-powered wells, and 21.5 TAF from diesel-powered wells. About 60 percent of the groundwater pumping capacity is available from Member Units north of the Yuba River, while the remaining 40 percent is from Member Units south of the Yuba River. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-51

98 Groundwater substitution transfers are typically released in July and August due to export limitations in the Delta, however, the Yuba Accord contains provisions about release scheduling for groundwater substitution transfers. Releases of portions of groundwater substitution transfers are scheduled by the Yuba Accord River Management Team (RMT) to provide better flow conditions for fish. The portion of the groundwater substitution transfer schedulable by the RMT depends upon the NYI. In a Schedule 1 year, all groundwater substitution transfer program releases will occur after July 1. In Schedule 2, 3, 4, and 5 years, the RMT can schedule up to 10 percent of the groundwater substitution transfer program s total volume. In Schedule 4 and 5 years, an additional 10 percent of the groundwater substitution transfer program s volume can be scheduled for release by the RMT after May 1. Releases of groundwater substitution transfers prior to the Yuba Accord were released in the months of July through September. Table shows the historical monthly release volumes of groundwater substitution transfers from New Bullards Bar Reservoir. Table Historical monthly release volumes of groundwater substitution transfers. Groundwater Substitution Release Volume (ac-ft) Year May Jun Jul Aug Sep Oct Total ,805 18,335-61, ,312 25,058 6,908-55, ,879 22,231 21, , ,000 46,116 33, , ,142 33, ,211 Total - 13, , ,343 25, ,404 Total (Yuba Accord) 1-13, ,489 88, ,986 Total Distribution - 4% 39% 49% 8% 100% Yuba Accord Distribution 1-7% 50% 43% 0% - 100% Base Case Distribution 10% 50% 40% 0% - 100% Key: ac-ft = acre-feet 1 Yuba Accord years are 2008, 2009 and It is highly probable that future groundwater substitution transfers would follow a pattern similar to that of recent transfers under the Yuba Accord. Accordingly, model simulations will assume a similar release pattern Released Transfer Water The historical monthly pattern of released transfer water for the 2001, 2002, and 2003 transfers is summarized in Table Because of Delta export limitations, the preferred transfer period is from July 1 to September As part of a water transfer program, YCWA may make available supplemental fisheries flows, typically in May and June, for flow stability. Under the Yuba 4 For the months of July, August, and September, the EWA Program has historically had 500 cfs of dedicated diversion capacity at the Banks Pumping Plant. EWA Program actions and CVPIA (b)(2) actions restrict pumping at Banks and Jones pumping plants in April, May, and June. During these months, the maximum allowable E/I ratio is Pumping capacity under the JPOD may be limited in October due to water quality concerns in the Delta. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

99 Accord, transfers are contained within flow requirements, and a detailed set of accounting rules (Exhibit 1 of the Water Purchase Agreement) determines what portion of the flow is considered transferrable. The Yuba Accord also contains provisions allowing for supplemental transfers, where YCWA would make discretionary releases to transfer additional water to the Yuba Accord Water Purchase Program participants. Any supplemental transfer requires YCWA to make an equivalent amount of water available to the RMT for release scheduling. Table Monthly pattern of historical water transfers. Transfer Volume (ac-ft) Year April May Jun Jul Aug Sep Oct Nov Dec Total 2001 c ,623 71,690 19, , c ,872 72,452 58,864 6, , ,886 34,384 14, , ,384-17,447 31,242 24,278 7,821 14,590 15,465 4, , c 14,154 17,018 22,598 42,488 42,006 11,987 10,203 5, , c , ,723 62,693 7,646 6, , c 56,438 56,239 27, ,856 Total (ac-ft) 23,538 17,018 93, , ,915 68,540 31,067 21,097 4, ,106 Total (%) 3% 2% 11% 36% 34% 8% 4% 2% 1% 100% Key: ac-ft = acre-feet BVID = Browns Valley Irrigation District DWR = California Department of Water Resources 1 Includes a 4.5 TAF BVID transfer to DWR. 2 Total transfer volume was 180 TAF, portions were released in January and February and backed into Lake Oroville for later release. 3 Includes groundwater substitution transfers as described in Table Includes 20,826 ac-ft of supplemental transfer. With the exception of supplemental transfers, as long as the Yuba Accord transfer program exists, transfer release timing will be determined by the Yuba Accord water purchase agreement. While unlikely, supplemental transfers will likely be scheduled for release in June through September, with 50 percent of the supplemental transfer in June Implementation of Transfers in Modeling The YRDPM includes the ability to simulate both stored water and groundwater substitution transfers Simulation of Stored Water Transfers Simulation of stored water transfers requires a timeseries in the input DSS file describing the desired release pattern. The YRDPM adds the release pattern to the Marysville flow requirement, and reduces the New Bullards Bar Reservoir target storage by an amount equivalent to the cumulative annual volume of the storage, to date. This ensures the transfer is released from storage, and is not merely a part of releases to meet the target storage. At the end of the transfer period, New Bullards Bar Reservoir storage should be lower than the target storage by a volume, at a minimum, equivalent to the total transfer volume. If operations are controlled by Yuba River flow requirements, cumulative Yuba River flow at Marysville should be greater than Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-53

100 the minimum flow requirement by a volume equivalent, at a minimum, to the desired transfer volume Groundwater Substitution Transfers Simulation of groundwater substitution transfers includes the reduction of agricultural demand at Daguerre Point Dam by a volume equivalent to the transfer volume, and an increase in Yuba River flow at Marysville similarly equivalent to the desired transfer volume. The reduction of demand at Daguerre Point Dam and the increase in Yuba River flow at Marysville do not need to occur simultaneously. As shown in Tables and 7.7-3, groundwater pumping typically begins in April or May; since water is not typically released for transfer until June or July, the reduced agricultural demand in April and May results in an increase in New Bullards Bar Reservoir storage. This is represented by an increase in the target operating line equivalent to the assumed daily pumping volume, allowing for additional water to be stored in New Bullards Bar Reservoir. When the groundwater substitution transfer is released, there is an increase in Marysville flow requirement and a decrease in New Bullards Bar Reservoir target operating line similar to stored water transfers. Also, since groundwater pumping has historically occurred in October and November, the model allows for the transfer to be released from New Bullards Bar Reservoir before it has been pumped; reductions in demand due to pumping after September repays the water previously released from New Bullards Bar Reservoir storage. Annual volumes of groundwater substitution transfers are defined within the model on the Transfers worksheet, and the typical pattern for pumping can be input as a monthly value on the Inputs-Timeseries worksheet. The release pattern can be defined as either monthly values on the Input-Timeseries worksheet or as an input timeseries from the input DSS file. 8.0 Model Simulation Process The YRDPM includes a series of routines. The primary model controls are contained on the worksheet, Scenario Builder and Control. Most user inputs are managed on this worksheet. After ensuring all variables are correct, the user clicks the button labeled, Run Model, and starts the YRDPM. Starting the YRDPM triggers a series of routines described below in the order they are executed. RunModel Initiated by the Run Model button. Collects input information, computes period of record information, determines water year, the number of days in the water year, calls other subroutines and passes the water year and number of days those subroutines. ClearYear Initiated by the RunModel routine. Clears all of the computation data from the spreadsheet from previous simulations. DateSet Initiated by the RunModel routine. Sets up date information for one year, including the start and ending date of the current simulation water year. Load_DSS_Data_Click Initiated by the RunModel routine. Executes the Load_DSS_Data routine. Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

101 Load_DSS_Data Initiated by the Load_DSS_Data_Click routine. Uses the HEC dynamic link libraries (DLL) to read information from a user-specified input DSS file and write it to locations specified on the DSS_Index worksheet. DSSFile_Open Initiated by the Load_DSS_Data routine. Uses the HEC DLL to open the user-specified DSS file. StartingConditions Initiated by the RunModel routine. Sets up conditions for or subsequent routines, including carrying over information from previous years simulation like storages or delivery allocations. LogCabin_OurHouse Initiated by RunModel routine. Simulates operations of Log Cabin and Our House dams, allocating inflows to either meeting flow requirements below the dams or for diversion into the dams respective tunnels. YearType Initiated by RunModel routine. Using user-specified flow requirements computes either North Yuba Index or Yuba River Index and writes it to Englebright Pool worksheet. NBBReleases Initiated by RunModel routine. Sets up NBB Pool for use in later routines. Writes New Bullards Bar Reservoir operating storage lines and evaporation rates to NBB Pool worksheet. Operations Initiated by RunModel routine. Primary operational simulation routine. It makes almost all release decisions for New Bullards Bar and Englebright reservoirs based on rules specified within the code and as(in?) inputs. After determining initial releases from New Bullards Bar Reservoir based on flow requirements below Englebright and New Bullards Bar Reservoir storage conditions, the routine makes modifications to New Bullards Bar Reservoir releases to accommodate Englebright storage fluctuations and flow fluctuation limitations below Englebright. DiversionDef Initiated by RunModel routine. Using end-of-september storage computed by Operations routine assuming full irrigation deliveries at Daguerre Point Dam, the DiversionDef routine applies a reduction in diversions to ensure New Bullards Bar Reservoir storage is at or above the carryover storage requirement. If there are any reductions in deliveries, the Operations and DiversionDef routines are rerun. ColgateOps Initiated by RunModel routine. Recomputes New Colgate Powerhouse releases based on user-defined Weekly Generation Factors pattern. The routine re-computes Englebright Reservoir storage accordingly. ColgateEngStorageCheck Initated by RunModel. Checks Englebright Reservoir storage against water surface elevation rules and makes additional adjustments to New Bullards Bar Reservoir releases to ensure Englebright Reservoir levels do not violate any rules. LowerYubaRiverFlow Initiated by RunModel routine. Computes Yuba River flows based on Englebright releases, Daguerre Point Dam diversions, various inflows. NarrowsSplit Initiated by RunModel routine. Splits previously-determined Englebright Reservoir power releases into Narrows 1 and Narrows 2 powerhouse releases based on userdefined rules. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-55

102 PowerGen Initiated by RunModel routine. Computes power generation at New Colgate, Narrows 1 and Narrows 2 powerhouses based on head and flow equation. AnnualDataGrabber Initiated by RunModel routine. Reads data from various worksheets and writes it to output worksheet. WaterBalance Initiated by RunModel routine. Checks to ensure water balance is maintained at New Bullards Bar and Englebright reservoirs and at Marysville. ReachOutput Initiated by RunModel routine. Computes and writes reach flow for all project reaches based on previously determined flows to the Reach Output worksheet. Write_DSS_Data_Click Initiated by RunModel routine. Runs the Write_DSS_Data routine to write simulation output to a DSS file. Write_DSS_Data Initiated by Write_DSS_Data_Click routine. Opens a user-specified DSS file using the DSSFile_Open routine, writes output to the DSS file using HEC DLL information and closes the DSS file. With the exception of the RunModel routine, YRDPM routines are set up to simulate up to one year at a time. Multi-year simulations are managed within the RunModel routine; it will loop one year at a time until the full simulation period has been completed. Since the ColgateOps routine requires the simulation period to end on a Sunday; it is possible for more or fewer than 365 days to be simulated in one step for multi-year simulations. However, each simulation will begin and end on the specified dates. 9.0 References Arndt, R. E. and J. S. Gulliver Hydropower Engineering Handbook, Brown, Luther P Hydraulic Turbines Part 3, State of California Department of Water Resources Yuba River Watershed Model; Division of Planning Memorandum Report. January State Water Resources Control Board (SWRCB) Revised Water Right Decision 1644 In the Matter of: Fishery Resources and Water Right Issues of the Lower Yuba River. July Order WR Order Approving Petition for Modification and Petition for Long-Term Transfer of Water. March 2008 United States Army Corps of Engineers (USACE) New Bullards Bar Reservoir Regulation for Flood Control. June 1972 United States Bureau of Reclamation and Department of Water Resources (DWR) Agreement Between the United States of America and the State of California for Coordinated Operation of the Central Valley Project and the State Water Project United States Federal Energy Regulatory Commission (FERC) Order Issuing New License. February Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

103 Order Modifying and Approving Amendment of License. November 2005 United States Federal Power Commission (FPC) Order Issuing License and Accepting Surrender of License. May P FPC Order Amending License (Major). FPC, Washington DC. May 6, 1966 United States Geological Survey (USGS) Water-Data Report CA Water Resources Data California Water Year 2004 Volume 4 Northern Central Valley Basins and the Great Basin from Honey Lake Basin to Oregon State Line, Yuba County Water Agency (YCWA) Draft Environmental Impact Report/ Environmental Impact Statement for the Proposed Lower Yuba River Accord. June Yuba River Basin Model: Operations and Simulation Procedures January Yuba County Water Agency and the California Department of Game Agreement. September 1965 Yuba County Water Agency and Pacific Gas and Electric Company Power Purchase Contract. May 1966 Zipparro, V. J. and H. Hasen, Eds Davis Handbook of Applied Hydraulics. Fourth Edition. McGraw-Hill. Water Balance/Operations Model Technical Memorandum 2-2 Attachment 2-2A November , Yuba County Water Agency Page A-57

104 Page Left Blank Attachment 2-2A Technical Memorandum 2-2 Water Balance/Operations Model Page A , Yuba County Water Agency November 2012

105 Technical Memorandum 2-2 Water Balance/Operations Model Attachment 2-2B Model Validation Report November , Yuba County Water Agency All Rights Reserved

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107 Table of Contents Section No. Description Page No. 1.0 Introduction...B Model Objective... B Model Overview... B Verification, Calibration and Validation Procedure... B Historical Years for Validation... B Model Overview... B Model Coverage... B Inputs... B Outputs... B Assumptions, Simplifications and Approximations Included in the Model... B Target Storage... B Englebright Management of Freshet Storm Flows... B Calibration...B Validation...B Model Configuration for the Validation Time Series... B Time Series Inputs for Validation Simulations... B Other Setup Parameters... B Groundwater Substitution Time Series... B Validation Results...B Validation Simulation Summary... B Validation Simulation Flows below Project Facilities... B Our House and Log Cabin Dams... B Flows below New Bullards Bar Reservoir and Dam... B New Colgate Powerhouse Flows... B Flows below Englebright Dam including Narrows 1 and Narrows 2 Powerhouse Releases... B Total Daguerre Point Dam Diversions and Flow at Marysville Gage... B Reservoir Storage... B Powerhouse Generation... B Validation Data Sets...B-35 Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page TOC-i

108 List of Figures Figure No. Description Page No Model Schematic with Reach Numbering....B Storage in New Bullards Bar Reservoir for Calendar Years 1986 to 2010, and Yuba Accord Target Storage Line with end of September Target Storage Values of 705,000 acre-ft and 650,000 acre-ft Identified....B New Bullards Bar Reservoir Target Storage Zone for the Baseline Condition versus Average Daily Storage for the Period of Record and Historical Average Daily Storage for 2006 to B Modeled and Historical Daily Average Flow below Englebright at Smartville Gage for Two Storms during Winter B Schematic of Streams, Dams and Tunnels in the Vicinity of Our House and Log Cabin Dams....B Mean Daily Flow at Below Our House Dam (USGS gage )....B Mean Daily Flow at Lohman Ridge Tunnel (USGS gage )....B Mean Daily Flow at Below Log Cabin Dam (USGS gage )....B Mean Daily Flow at Camptonville Tunnel (USGS gage )....B Mean Daily Flow below New Bullards Bar Dam (YCWA historical data used)....b Mean Daily New Colgate Powerhouse Release (USGS gage ) with 7 day moving average of historical releases....b Mean Daily New Colgate Powerhouse Release (USGS gage ) for Summer 2008, with weekend days shaded gray....b Mean Daily Flows below Englebright Dam (USGS gage )....B Mean Daily Release at Narrows 2 Powerhouse (USGS gage )....B Mean Daily Release at Narrows 1 Powerhouse (USGS gage )....B Mean Daily Total Diversion Flow at Daguerre Point Dam (BVID, Hallwood- Cordua and South Diversion)....B Mean Daily Flow at Marysville Gage (USGS gage )....B Storage in New Bullards Bar Reservoir....B Storage in New Bullards Bar Reservoir for Water Year 2001 through B Storage in Englebright Lake....B Power Generation at Colgate Powerhouse....B Power Generation at the Narrows 2 Powerhouse....B-34 Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page TOC-ii 2012, Yuba County Water Agency November 2012

109 List of Tables Table No. Description Page No YRDP Model Hydrologic Input Data and DSS F Part Names....B Operations Inputs for the YRDP Model....B YRDP Model Output and DSS Names....B Scenario Builder and Control Tab Settings....B Input-Constraints Tab Values....B Groundwater Substitution Transfer Pumping by Member Unit for 2008, 2009 and B Monthly Pumping and Release Percentages of Annual Groundwater Substitution Volume....B Mean Annual Flow at Gage locations at Our House Dam and Log Cabin Dam....B Annual Mean Release from new Colgate Powerhouse (USGS Gage )....B Annual Mean Flows below Englebright Dam....B Annual Mean Flows for Total Diversions and at Marysville Gage....B Annual Mean Daily Powerhouse Generation (MWH)....B-35 Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page TOC-iii

110 Page Left Blank Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page TOC-iv 2012, Yuba County Water Agency November 2012

111 1.0 Introduction The Yuba County Water Agency (YCWA or Licensee) has developed a water balance/operations model to simulate the operations of the (Project), Federal Energy Regulatory Commission (FERC) License No This report presents a description of the methods used to calibrate, verify and validate the model and to present the results of those efforts. For a complete description of the model please refer to Yuba River Development Project, FERC License No Operations Modeling Report, dated June The Yuba River Development Project Water Balance/Operations Model (YRDP Model) is based in Microsoft Excel and extensively utilizes Visual Basic Advanced programming language to perform data input and output, date management and most aspects of calculating flows, storage and power generation. Model run setup for simulating a scenario of variable operational parameters is accomplished through selection and input of items across several worksheets. The Model uses a daily time step and simulates all elements of Project operations that are expected to affect flow, storage and power generation at a daily time step. Post-processing is used to disaggregate the operations of the Colgate Powerhouse from mean daily values to representative hourly operations. 1.1 Model Objective Objectives of the YRDP Model are to simulate operations for a period of analysis that covers a range of conditions that reflect historical hydrology. The YRDP Model should also address operational decisions made during Project operation including: flood control (reservation of flood storage); water supply; recreation; instream flows; and hydropower generation. YRDP Model objectives also include: Accurately reproducing observed reservoir levels, reservoir releases, and hydropower generation, within acceptable calibration standards over a range of hydrologic conditions; Providing output to inform other studies, analyses, and models; Allowing simulation of changes in Project operations to determine effects on reservoir levels, reservoir releases and hydropower generation. To accomplish this accurate simulation, the YRDP Model must 1) reasonably represent the physical character of the Project, and 2) accurately portray a real world implementation of operational criteria. Critical to achieving accurate, real-world results is a data set of input hydrology that accurately represents historic hydrology. The report entitled Hydrology Report discusses development of the YRDP Model s input hydrology data set. This report demonstrates that the input hydrology data set is of high quality, as all major input flows to the system used for the baseline historical hydrology are derived from or direct observations at U.S. Geological Survey (USGS) gaging stations. Since a statistically significant time period of 39 years of hydrology is used for the data set, it can be concluded that the range and frequency of wet to dry hydrologic conditions is represented. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-1

112 1.2 Model Overview The YRDP Model was developed to simulate the operations of the Project on a daily time step for the period of October 1, 1969 to September 30, The following streams, Project facilities and other features are included in the YRDP Model: The North Yuba River below Goodyears Bar Slate Creek below the Slate Creek Diversion Dam Canyon Creek at its confluence with the North Yuba River New Bullards Bar Dam and Reservoir The Middle Yuba River from immediately above Our House Dam Oregon Creek from immediately above Log Cabin Dam Our House Dam Log Cabin Dam The Lohman Ridge Tunnel The Camptonville Tunnel The South Yuba River below Jones Bar Deer Creek below the Deer Creek near Smartville Gage Colgate Powerhouse New Bullards Bar Dam Fish Hydro Englebright Dam and Reservoir Narrows 1 and 2 powerhouses Daguerre Point Dam YCWA agricultural diversions Smartville gage Marysville gage Yuba River from the confluence of the North and Middle Yuba rivers to the Feather River The YRDP Model simulates daily operations of the project by loading a full water year (or partial year for the first year of simulation if starting on a date other than September 30th) of inflow data, and then simulating the various project operational rules, incorporating the physical constraints of the system sequentially determining project releases for each day of the current water year. Results are output in U.S. Army Corps of Engineers Hydrologic Engineering Center (HEC) Data Storage System (DSS) format. Figure is a schematic of the Yuba River watershed: modeled features are identified and reaches are numbered. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

113 Source: MWH Americas, Inc. Figure Model Schematic with Reach Numbering. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-3

114 1.3 Verification, Calibration and Validation Procedure The process of completing a mathematical model after it has been coded includes three steps, verification, calibration and validation. These steps occur in parallel with model development and they usually result in corrections and modifications to the model. Verification is the process of checking lines of code to ensure that calculations and data manipulation are done correctly. An example of model verification would be checking that a formula is used correctly, that the program code implements the formula correctly and results passed to the next model step or which are stored is done correctly. Calibration is the process of adjusting variable parameters so that known results are produced when modeling a known set of inputs. Validation means that a model is acceptable for its intended use because it meets specified performance requirements. 1 The validation process for the YRDP Model includes comparing model results of streamflow, reservoir storage and power generation with historical data, when historical conditions are modeled. For the YRDP model, verification and calibration work were a continuous process throughout the development to complete code sections Historical Years for Validation Validation of the YRDP Model was conducted for two series of water years through 2010 represents the current operational regime that includes the Yuba River Accord (Yuba Accord), which was implemented as a long term program in 2008 and separate validation of the YRDP Model s continuous simulation capacity was conducted for the ten-year period of water years 2001 to The selection of years for the three-year simulation was because these years represent a range of hydrology and most closely represent current (baseline) operations, including the baseline streamflow requirements of the Yuba Accord. Annual unimpaired flow volumes of the Yuba River at Smartville for the three years of validation are 50%, 72% and 77% of the 50-year average unimpaired runoff volume (1961 to 2010). Although the annual unimpaired volumes for 2009 and 2010 are relatively close, the snowpack and resulting spring and early summer runoff of 2010 were much greater than in While the April through July 2009 unimpaired runoff of the Yuba River at Smartville was 84 percent of average, the April to July 2010 unimpaired runoff was 120% of average or about 50% greater in 2010 than Conversely, the late fall and winter 2009 unimpaired runoff was almost 50% greater than the runoff for the same period of Therefore these two years provide hydrology that included a wet winter and dry spring (2009) and a dry winter and wet spring (2010) for validating the model. The intent of including the simulation of a longer series of years is to demonstrate the YRDP Model s ability to represent a wide range of year-to-year hydrology, showing that the YRDP Model does not diverge from historical flow and storage amounts, but re-converges to subsequent year historical conditions, even under individual year variance. Through the 2001 to 2010 historical period, many unique and changing circumstances have occurred which affected flow and storage conditions: e.g., individual decisions that were made in managing storage and anticipated snowmelt runoff, or were operational practices that are no longer used. It is not the 1 Edward J. Rykiel Jr. Testing ecological models: the meaning of validation Center for Biosystems Modeling, Industrial Engineering Department, Texas A&M University Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

115 intent of the 2001 to 2010 validation series to capture all, or even most of these occurrences, but rather to demonstrate that the YRDP Model results provide a reasonable approximation of the hydrologic conditions even without incorporating these unique operations into the YRDP Model. 1.4 Model Overview The YRDP Model utilizes a daily time step for operations simulation. Some of the decisions are made using a weekly volume, as described below. The YRDP Model has the capability of simulating time periods from as long as 41 years of hydrology (water years 1970 through 2010) and as short a time interval as several days. All simulations must run through September 30, though as discussed below, depending on simulation options, the YRDP Model could simulate as much as six extra days past September 30th. Internally, the YRDP Model simulates as much as a single year at a time; it reads input and writes output for as much as one year at a time. Longer durations require subsequent internal iterations of reading input and writing output; however, from a user s perspective, multiple years and single years are managed in the same way. Flows in the Yuba River and its tributaries have been gaged by several agencies for varying lengths of time. Generally, a reliable mean daily flow record for major watershed streams exists from 1969 to the present day. Given the availability and reliability of these gaged flow data, flow measurements for the period of record of October 1969 through September 2010 were selected for inclusion in the compiled hydrologic data set for inflows to the Project area Model Coverage The YRDP Model includes the following streams, Project facilities, and other features: The North Yuba River below Goodyears Bar Slate Creek below the Slate Creek Diversion Dam Canyon Creek at its confluence with the North Yuba River New Bullards Bar Dam and Reservoir The Middle Yuba River from immediately above Our House Dam Oregon Creek from immediately above Log Cabin Dam Our House Dam Log Cabin Dam The Lohman Ridge Tunnel The Camptonville Tunnel The South Yuba River below Jones Bar Deer Creek below the Deer Creek near Smartville Gage Colgate Powerhouse Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-5

116 New Bullards Bar Dam Fish Hydro Englebright Dam and Reservoir Narrows 1 and 2 powerhouses Daguerre Point Dam YCWA agricultural diversions Smartville gage Marysville gage Yuba River from the confluence of the North and Middle Yuba rivers to the Feather River The YRDP Model simulates operations of the Project by routing inflows to New Bullards Bar Reservoir, Our House Dam, Log Cabin Dam, Englebright Reservoir, and the Lower Yuba River through the various facilities and features in the Project Area. Inflows to Our House Dam on the Middle Yuba River are routed either to the lower Middle Yuba River or into the Lohman Ridge Tunnel, flowing to Oregon Creek. There, the flow from the Lohman Ridge Tunnel is combined with Oregon Creek inflow to be released at Log Cabin Dam to either lower Oregon Creek or into the Camptonville Tunnel. The Camptonville Tunnel flows are released into New Bullards Bar Reservoir and releases to lower Oregon Creek combine with Middle Yuba River flows and area accretions to flow into the Yuba River. On the North Yuba River, inflows above Goodyears Bar combine with Slate Creek inflows and area accretions to flow into New Bullards Bar Reservoir. All inflows to New Bullards Bar Reservoir are either stored or released to the Yuba River at Colgate Powerhouse or North Yuba River below the Dam: a portion of the New Bullards Bar Reservoir releases are made to the North Yuba River and the remainders are released several miles downstream at Colgate Powerhouse to the Yuba River. Releases to the North Yuba River at the dam combine with flows from the Middle Yuba River to form the headwaters of the Yuba River. Several miles downstream of the confluence of the North and Middle Yuba rivers, Yuba River flows combine with releases from Colgate Powerhouse to flow into Englebright Reservoir where they are combined with inflow from the South Yuba River Inputs YRDP Model inputs are classified into two categories: hydrologic input and operational input. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

117 Hydrologic Input Hydrologic input to the YRDP Model is read as a timeseries from a DSS file. Table indicates the input description and its name in the input DSS file. As previously mentioned, all input timeseries contain daily records for the period of October 1, 1969 through September 30, Table YRDP Model Hydrologic Input Data and DSS F Part Names. Description Accretions from Canyon Creek Deer Creek Inflow Daguerre Point Agricultural Diversion Demand Dry Creek Inflow Total Accretions to Englebright Reservoir Accretions to the Englebright Reservoir Area Accretions to the Middle Yuba River below Oregon Creek Accretions to the Middle Yuba River above Oregon Creek Accretions to the North Yuba River below Goodyears Bar Accretions to Oregon Creek below Log Cabin Dam Accretions to Slate Creek below the Slate Creek Diversion Dam Accretions to the South Yuba River below Jones Bar Middle Yuba River Inflow above Our House Dam Total Accretions to New Bullards Bar Reservoir Accretions to the New Bullards Bar Reservoir Area North Yuba River Inflow above Goodyears Bar Oregon Creek Inflow above Log Cabin Dam Slate Creek Inflow below the Slate Creek Diversion Dam South Yuba River Inflow at Jones Bar DSS F Part Name CANYON_CR_ACC DEER_CR DGP_DEM DRY_CK EB_ACC ENG_RES_ACC LOWER_M-YUBA_LOW_ACC LOWER_M_YUBA_MID_ACC LOWER_N_YUBA_ACC LOWER_OREGON_CK_ACC LOWER_SLATE_CR_ACC LOWER_S_YUBA_ACC M_YUBA NBB_ACC NBB_RES_ACC N_YUBA OREGON_CK SLATE_CR S_YUBA Operations Input Many of the user inputs are not time series and must be input by hand. Operational inputs fall into several categories: Simulation Variables - Variables related to running the simulation such as starting date, initial conditions and various on/off switches Operational Parameters - Variables related to Project operations not tied to a specific regulatory requirement or agreement such as carryover storage factors Regulatory Requirements and Agreements - Instream flow requirements and ramping constraints Infrastructure/Capacity Inputs - Physical capacities and elevations of the various Project facilities. Table lists operations user-inputs for the YRDP model. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-7

118 Table Operations Inputs for the YRDP Model. Operations Input Start Date End Date Starting NBB Storage Starting Englebright Storage Use Automatic Calculations Throughout? Calculate Water Balance? DSS Input File DSS Output File Simulation Name: Use Weekly Power Generation Factors? Scenario File Name Scenario Name Level of Development Target Operating Line Drought Level of Protection (for Carryover Storage) Maximum Carryover Storage Delivery Target (for Carryover Storage) Maximum Deficiency Maximum September & October Release Above Minimums Maximum Colgate Release Reduction for Englebright Spill Avoidance Narrows 1 & 2 Flow Split Power Generation Factor Settings Our House Dam Release Buffer Log Cabin Release Buffer Flood Pool Buffer Target Operating Line Volume above Target Line Volume below Target Line Target Englebright Storage Elevation Trigger for Max Narrows: Evaporation Rate Carryover Storage Operation Buffer Evaporation Description Simulation Variables Initial date of simulation Final date of simulation Initial storage of New Bullards Bar Reservoir Initial storage of Englebright Reservoir Yes/No switch to select whether or not automatic calculation is used in each simulation step Yes/No switch to select whether or not the model does a water balance check at each location for each time step Path and file name of DSS file containing hydrologic input time series data Path and file name of DSS file for the model to write output to. Can be either a new file or an existing one Name used as the F-Part when writing output to the DSS output file Yes/No switch to select whether or not weekly Colgate generation is reshaped according to power generation factors File containing the scenario data. Can be a new file or an existing one. Name of the scenario used when writing to the Scenario File Operational Parameters Level of development for agricultural diversion demand New Bullards Bar Reservoir target operating line Exceedance probability of drought used to calculate minimum end-of-september New Bullards Bar Reservoir storage Greatest volume of computed minimum required end-of-september New Bullards Bar Reservoir storage Minimum allocation of agricultural deliveries for following year used to compute minimum required end-of-september New Bullards Bar Reservoir storage Maximum deficiency of agricultural deliveries before reducing instream flows Maximum allowable release above minimum required flow in September and October Maximum reduction in Colgate releases to avoid spills from Englebright reservoir due to high flows on the Middle and South Yuba rivers Defines which method used to split Englebright releases between the Narrows 1 and 2 powerhouses Used to redistribute Colgate releases throughout a week to simulate weekly operations. Used to add a buffer to required flow below Our House Dam Used to add a buffer to required flow below Log Cabin Dam Buffer on flood pool, used to determine if Colgate releases can be reduced for Englebright spill avoidance Target storage in New Bullards Bar Reservoir. The model will make releases to reduce storage to this level, subject to an upper and lower buffer. Releases for target operating line are limited to non-spill releases. When New Bullards Bar Reservoir storage is between the Upper and Lower target lines, releases are linearly interpolated between maximum Colgate capacity and releases for instream flow requirements. Added to Target Operating Line to define Upper Target Line. If New Bullards Bar Reservoir storage exceeds the Upper Target Line, releases will be made at full Colgate Capacity Subtracted from Target Operating Line to define Lower Target Line. If New Bullards Bar Reservoir storage is less than the Lower Target Line, releases will be limited to meeting instream flow requirements. Ideal end-of-day Englebright Reservoir storage. If storage is below the Target Englebright Storage, New Bullards Bar Reservoir releases may be increased. If storage is above the Target Englebright Storage, New Bullards Bar Reservoir may be decreased. Englebright Reservoir water surface elevation which, if exceeded, could result in maximum release through the Narrows powerhouses Monthly evaporation rate (in inches) for Englebright or New Bullards Bar Reservoirs. Volume of buffer above FERC Minimum Pool Assumed annual evaporation in TAF for purposes of determining carryover storage requirement Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

119 Table (continued) Operations Input Yuba County Water Agency Description Regulatory Requirements and Agreements Instream Flow Requirements Controlling minimum instream flow requirements Hydrologic Index Hydrologic Index used for the Instream Flow Requirements Starting Year Type The hydrologic year-type for the starting date September 15 to October 31 Flow Reduction Maximum allowable reduction of flows below Englebright between September 15 and October 31. From the Narrows 2 Bypass FERC Amendment November 1 to March 31 Maximum Flow Reduction Maximum allowable reduction of flows below Englebright between November 1 and March 31. From the Narrows 2 Bypass FERC Amendment Maximum Daily Flow Reduction Maximum daily reduction in flow below Englebright Reservoir for any time of the year. From the Narrows 2 Bypass FERC Amendment Instream Flow Requirement Below Our House Dam Required Middle Yuba River flow below Our House Dam. Currently defined by FERC License 2246 and 1965 YCWA-DFG Agreement Instream Flow Requirement Below Log Cabin Dam Required Oregon Creek flow below Log Cabin Dam. Currently defined by FERC License 2246 and 1965 YCWA-DFG Agreement Flow Requirements at Smartville Daily average Yuba River flow requirement at Smartville, as measured at the Smartville gage Flow Requirement at Marysville Daily average Yuba River flow requirement at Marysville, measured at the Marysville gage Englebright Minimum Pool Elevation Minimum storage target for Englebright Reservoir, currently defined by Pacific Gas and Electric (PG&E) agreement with Englebright marinas Fish Hydro Release Continuous release through the Fish Hydro powerhouse at the base of New Bullards Bar Dam. Meets instream flow requirement currently defined in FERC License 2246 and 1965 YCWA-DFG Agreement Infrastructure and Capacity Inputs Lohman Ridge Tunnel Capacity Camptonville Tunnel Capacity Colgate Max Maximum Storage Englebright Dam Crest Elevation Englebright Area Narrows 1 Capacity Narrows 2 Capacity Colgate Efficiency Colgate Turbine Elevation Narrows Efficiency Narrows Tailwater Elevation: Physical capacity of Lohman Ridge Tunnel Physical capacity of Camptonville Tunnel Maximum release capacity of Colgate Powerhouse Maximum storage of New Bullards Bar Reservoir, including surcharge space Elevation of Englebright Dam crest. Water surface elevation in excess of this elevation will result in spill Assumed area of Englebright Reservoir at 40,000 acre-feet of storage Maximum release capacity of Narrows 1 Powerhouse Maximum release capacity of Narrows 2 Powerhouse Assumed efficiency of Colgate Powerhouse. Used to determine generation Elevation of Colgate Powerhouse turbines. Used to determine head differential and resulting generation Assumed efficiency of combined Narrows 1 and Narrows 2 powerhouses. Used to determine generation Assumed normal water surface elevation of Yuba River for both Narrows 1 and Narrows 2 powerhouses. Used to determine head differential and resulting generation Outputs In addition to outputting regulated flow and cumulative flow for each of the reaches in Figure 1.4-1, the YRDP Model outputs storage, flow, elevation, and generation information for all project components. Table indicates the output description, and its name in a standard output DSS file. The table does not list the output for the reaches Figure 1.4-1, those output are simply labeled according to their reach number (i.e. REACH_001 for Reach 1) with a DSS data type of either REG_FLOW for regulated flow or NAT_FLOW for natural flow. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-9

120 Table YRDP Model Output and DSS Names. Description DSS F Part Name DSS Data Type Flow Through the Camptonville Tunnel CAMPTONVILLE_TUNNEL FLOW Flow Through the Colgate Powerhouse COLGATE_FLOW FLOW Generation from the Colgate Powerhouse COLGATE_GEN POWER Agricultural Delivery Allocation DGP_ALLOC SHORTAGE Agricultural Diversion Demand DGP_DEM FLOW Agricultural Diversion DGP_DIV FLOW End-of-Day Water Surface Elevation of Englebright Reservoir ENG_ELEVATION ELEVATION Evaporation from Englebright Reservoir ENG_DVAP EVAPORATION Total Releases from Englebright Dam ENG_RELEASE FLOW Spills from Englebright Reservoir ENG_SPILL FLOW Englebright Reservoir End-of-Day Storage ENG_STOR STORAGE Englebright Reservoir End-of-Day Storage Target ENG_STORAGE_TARGET STORAGE Water Balance Check around Englebright Reservoir ENG_WBAL SUM New Bullards Bar Reservoir Fish Hydro Release FISH_HYDRO FLOW Minimum Instream Flow Requirement below Log Cabin Dam LOG_CABIN_MIF FLOW Releases to Oregon Creek from Log Cabin Dam LOG_CABIN_RELEASE FLOW Flow in the Lohman Ridge Tunnel LOMANRIDGE_TUNNEL FLOW Yuba River Flow at the Marysville Gage MRY_FLOW FLOW Minimum Instream Flow Requirement at the Marysville Gage MRY_MIF FLOW Water Balance Check at the Marysville Gage MRY_WBAL SUM Release through the Narrows 1 Powerhouse NARROWS1_FLOW FLOW Generation at the Narrows 1 Powerhouse NARROWS1_GEN POWER End-of-Day Water Surface Elevation of New Bullards Bar Reservoir NBB_ELEVATION ELEVATION Evaporation from New Bullards Bar Reservoir NBB_EVAP EVAPORATION End-of-Day Storage of the New Bullards Bar Reservoir Flood Pool NBB_FLOOD_POOL STORAGE Lower End-of-Day New Bullards Bar Reservoir Operating Line NBB_LOWERTARGET_LINE STORAGE Total Daily Release from New Bullards Bar Reservoir NBB_RELEASE FLOW Spill from New Bullards Bar Reservoir NBB_SPILL FLOW End-of-Day New Bullards Bar Storage NBB_STORAGE STORAGE Upper End-of-Day New Bullards Bar Reservoir Operating Line NBB_UPPERTARGET_LINE STORAGE Water Balance Check at New Bullards Bar Reservoir NBB_WBAL SUM North Yuba Index Value NYI INDEX North Yuba Index Year-Type NYI YEARTYPE Required Minimum Instream Middle Yuba River Flow Below Our House Dam OUR_HOUSE_MIF FLOW Release to the Middle Yuba River from Our House Dam OUR_HOUSE_RELEASE FLOW Yuba River Flow at Smartville SMV_FLOW FLOW Required Minimum Instream Yuba River Flow at Smartville SMV_MIF FLOW 1.5 Assumptions, Simplifications and Approximations Included in the Model The YRDP Model is a simplified, approximate simulation of physical facilities and major portions of the Yuba River watershed stream system, and necessarily includes computations that are intended to reasonably portray the storage and flow conditions that would occur under realworld hydrology. Certain physical conditions are included in the YRDP Model using simplifying assumptions and operational elements use approximations to attain reasonably accurate results. The following is a brief description of the major assumptions used in the YRDP Model, and YRDP Model approximations that mimic real-world operational decisions. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

121 Major simplifying assumptions included in the YRDP Model are: No routing of flows (i.e. flows are daily averages with zero travel time between nodes) Release capacity of all powerhouses is not head-dependent (fixed maximum flow) No stream storage is present (i.e., storage is only at reservoirs and not in stream reaches) All irrigation diversions are made at one model node, Daguerre Point Dam Accretions of local flow enter the stream at the downstream node of the relevant reach Flood flows entering New Bullards Bar Reservoir that result in flood pool encroachment are released under a simplified set of rules that approximate daily release volumes that would occur under real-time operations to the Flood Control Manual The real-world decision process to determine water releases at the various facilities is complex and includes an assessment of the physical state of the watershed and anticipated future conditions. In YRDP Model simulations, a surrogate approximation is used in place of this complex set of decision variables. Release decisions in the YRDP Model are separated into two fundamental categories: releases to meet downstream requirements and constraints; and release to manage reservoir storage. Decisions to determine the amount of water to be released to meet downstream requirements and constraints are absolute and do not require approximations. Downstream regulatory requirements at specified locations, as well as diversion amounts that reduce stream flow are known. For each day of simulation, the determinations of releases to meet downstream requirements are made based on simple calculations. Releases to manage storage are more complex and subject to many influencing factors, therefore requiring an approximate method in the YRDP Model Target Storage Decisions to determine the amount of water to be released to manage storage in New Bullards Bar Reservoir are not absolute, and in real-world instances these decisions are made with imperfect and incomplete knowledge about watershed state and future inflows to reservoirs. In actual operations, assessments of future inflow are made and a range of possible release patterns are examined to determine the best course of action to ensure a safe, compliant and efficient operation. For the YRDP Model simulation, a more generalized approach is taken. Through examination of historical operations of reservoir storage and the use of calibration techniques to run simulations and determine the preferred storage state throughout the water year for a range of hydrology and water shed conditions, a target storage time series has been determined. Target storage is the idealized amount of reservoir storage for a given date that provides the best solution to manage water to meet system demands and operational objectives over a range of possible future inflows. A target storage line is the series of daily values of target storage throughout the year. A target storage line is also unique to the system constraints that are in place which impact operations. For example, the target storage line would likely change with significant changes to downstream demands, such as differing instream flow requirements. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-11

122 Historically, target storage has varied as system demands and operational objectives have changed. Therefore the current target storage line is not identical to target storage for years prior to 2006, which was the first year of the Yuba River Accord Pilot Program. However, the historical record of storage in New Bullards Bar Reservoir from 1986 to 2010 shows that the current target storage is centered within the range of historical operation. Figure is a plot of historical New Bullards Bar Reservoir storage for calendar years 1986 to 2010 as well as the current target storage line depicted as a thick red line. Two other points are shown on the figure: the end of September target storage values of 705,000 acre-ft, which was the target end of year storage prior to 2006 before the Yuba Accord, and the target storage of 650,000 acre-ft which is the current end of September (end of water year) target storage used with the Yuba Accord. As seen in the figure, end of September storage is clustered into three groups: 1) years prior to 2006 in which runoff was sufficient to achieve and end of September target storage of 705,000 acre-ft, 2) years since 2006 that have achieved an end of September target storage just under 650,000 acre-ft and 3) drier years before and after 2006 where storage was low due to low runoff. Figure Storage in New Bullards Bar Reservoir for Calendar Years 1986 to 2010, and Yuba Accord Target Storage Line with end of September Target Storage Values of 705,000 acre-ft and 650,000 acre-ft Identified. The modeled implementation of target storage is done with buffers to the target storage line. For generally set monthly or semimonthly periodic dates throughout the water year, an upper buffer volume and lower buffer volume are input. When added to the target storage for the upper buffer and subtracted from the target storage for the lower buffer, the result is an Upper Target Storage and a Lower Target Storage. These target storage lines define a zone of storage that determines an operational response to storage conditions and inflow rates. The implementation of this zone Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

123 defined by the upper and lower target storage is a logical response to storage level within the zone, which is the approach taken in actual operations of the reservoir. For a given date, if storage is in the upper range of the zone releases are increased, and if storage is in the lower range of the zone releases are decreased. The implementation of this operation in the YRDP Model is to use the upper and lower target storage lines to define the upper and lower range of non-flood operation releases. At the upper target storage line, releases are made at the maximum powerhouse capacity, which is 3,430 cfs for Colgate Powerhouse. At the lower target storage line, releases are made to the minimum allowed release, which is to satisfy required flows plus any losses, which would include downstream diversions. The result is that if the runoff rate is greater than the release rate needed to meet downstream demands, the YRDP Model will operate the reservoir in the target storage zone, as long as inflow is lower than the maximum release rate of the Colgate Powerhouse. Figure is a graph of the upper and lower target storage in New Bullards Bar Reservoir for the calendar year, with the target storage zone shaded in blue. The daily average modeled baseline storage (for the full period of simulation of 1970 to 2010) is shown as a black line and the historical average daily storage (2006 through 2011) is shown in orange. The bottom of the Flood Pool is shown as a purple line. The figure shows that, on average, the YRDP Model achieves the target storage for most of the winter and spring when runoff is sufficient to support the targeted storage. The figure also shows that the simulated average daily storage for the period of record is very similar for the entire year to the recent historical operation under the Yuba Accord. Figure New Bullards Bar Reservoir Target Storage Zone for the Baseline Condition versus Average Daily Storage for the Period of Record and Historical Average Daily Storage for 2006 to Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-13

124 1.5.2 Englebright Management of Freshet Storm Flows Inflow into Englebright Reservoir consists of partially-controlled inflow from storage and release operations at New Bullards Bar Reservoir on the North Yuba River and uncontrolled inflows from the Middle and South Yuba rivers. Peak flows from rainstorm runoff into Englebright Lake have historically been managed using two mechanisms: 1)reduction of releases from Colgate Powerhouse, resulting in lowering of Englebright storage in anticipation of a storm, and 2) temporary increase in releases from Englebright once storm inflow commences, continuing until storm inflow subsides and Englebright storage reduces back to normal levels. These operations are coded into the model in simplified forms to generally mimic the release patterns that occur in response to storm events. Both mechanisms have been used historically, but the second (increasing Englebright releases when storage rises above the normal pool upper range at about elevation 523 ft msl), is the current operation that is used consistently to manage storm flows. An example of this operation is seen in Figure 1.4-3, which is a graph of historical and modeled daily average flows below Englebright Dam at the Smartville gage for late February into early March of The graph shows two storms during that period. For both storms the modeled peak average daily flow occurs on the same day as the historical flow, however is within 7 percent of the historical peak flow for the first storm and within 1 percent of the second storm peak flow. Figure Modeled and Historical Daily Average Flow below Englebright at Smartville Gage for Two Storms during Winter Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

125 2.0 Calibration A deterministic water balance operation model usually has very few calibrated parameters, if any. Most calculations of flow are simple addition for gains and subtractions for losses. For the YRDP Model, the only calibrated parameters are the target storage line, which was discussed in the previous section, and the determination of power generation from the powerhouses. The Modeling Report describes, in detail, the methodology and resulting parameters that are used in the model to convert head and flow to generation. Plots of modeled versus historical generation for the New Colgate Powerhouse and Narrows 2 Powerhouse are included under Section 4 of this report. 3.0 Validation The validation process for the YRDP Model includes running a model simulation that uses historical hydrology and conditions to obtain streamflow, diversions, reservoir storage and power generation and then comparing those results both quantitatively and qualitatively with historical data. As stated in the overview, the intent of validation is to demonstrate that the YRDP Model provides reasonably accurate results for simulation of watershed hydrology and YRDP facility operations. Statistical summary tables are provided for key results. A static accuracy level to determine pass or fail of the validation is not used for this work. Instead, the review of validation results for each output includes a general discussion of the relative significance of variation or agreement with historical data. This is done because one-size-does-not-fit-all for validation. As an example, a 10% variation on a flow at a key location that is 2,000 cfs and therefore has a variation of 200 cfs could be a significant deviation from historical data, whereas a 10% variation from historical data at a location that has a flow of 30 cfs and thus a 3 cfs variation may not have any significance. It is the opinion of the Licensee that the YRDP Model meets the intended purpose for supporting the relicensing process and reasonably simulates the hydrology of the Yuba River watershed as well as providing an accurate simulation of the YRDP facilities and operations. 3.1 Model Configuration for the Validation Time Series Current day operations differ in a number of ways from past operations. Some of these differing operations are due to regulatory changes, such as the Yuba Accord; some are due to changes in power operations driven by market and energy demand changes in California; and other changes are discretional changes based on new information or newer approaches to meeting all of the constraints on the system to achieve a more efficient operation. The following is a summary description of the model configuration of input variables and time series parameters for the two simulation periods. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-15

126 3.1.1 Time Series Inputs for Validation Simulations For simulation of the 2008 to 2010 period and the 2001 to 2010 period, a time series of daily values for several parameters are used in place of model generated daily values. The model includes two switches on the front page labeled Instream Flow Requirements and Time Series. For the Instream Flow Requirements switch Timeseries is selected. This forces the YRDP Model to use time series daily values for the Marysville Gage Required Flow and the Smartville Gage Required Flow. The second switch selection sets the Timeseries switch to Validation. This selection results in the YRDP Model using time series data for three additional parameters: diversions and the lower and upper target storage lines. The list of time series data that these switches engage in the YRDP Model simulation are the following: Marysville Gage Required Flow Smartville Gage Required Flow Daguerre Diversions New Bullards Bar Reservoir Lower Target Line New Bullards Bar Reservoir Upper Target Line Without these switches set, the YRDP Model would look up the Marysville Gage and Smartville Gage required instream flows by first setting the instream flow schedule that is to be used by referring to the Hydrologic Index switch on the front page, determining the index value for the current year of simulation, and then filling in the daily values of required flow for each day of the year by entering the table of semi-monthly required flows values that are located on the Inputs-Timeseries tab. Without the use of complete simulation period daily time series values for diversions and the upper and lower target lines, the YRDP Model would use the wet and dry year synthetic diversion data from the standard input file (used in the base case) and would look up the target line values from the table on the Inputs-Timeseries tab. Historically, for the period 2001 to 2007, operations were not always governed by just the required instream flows. In all dry years prior to 2008, additional water was released in the summer for stored water transfers and for most dry years, an additional amount of water was released as part of groundwater substitution transfers. At other times, additional releases were made to benefit fish during the fall spawning period. Use of a full simulation period time series for required flows allows for the simulation of these unique historical flows. In addition to these requirements, when simulating the ten-year period of 2001 to 2010, the instream flow standard changed. In 2008, the Yuba Accord went into effect on a permanent basis, where prior to this date the State Water Resources Control Board s Decision 1644 flow requirements were in place. The YRDP Model does not have the capability to change flow standards during a simulation. For diversions, the present-day diversion level has only been in place since 2010, when the Wheatland Canal started operations. Therefore, to properly represent historical diversions, a time series is used. Finally, because of these two historical differences (instream flows and diversion), a single annual time series of target storage values would not properly represent the Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

127 management of storage in New Bullards Bar Reservoir under differing downstream controlling demand for diversion and instream flows, and therefore a historical annually varying series is used. The YRDP Model groundwater substitution releases are automated stream flow controls used in the validation simulations for the 2008 to 2010 period for both the three-year and ten-year simulations. This calculation is to demonstrate the validity of the Model s ability to properly represent groundwater substitutions by inputting an annual groundwater substitution transfer volume. Except for the items listed above, all other model elements are identical to the base case simulation configuration Other Setup Parameters The following is a tabulation of the parameters used in the three-year and ten-year simulations. Table Scenario Builder and Control Tab Settings. Initial Conditions Starting NBB Storage: 702,880 (10 year) 618,296 (3 year) Starting Englebright Storage: 30,947 Starting Delivery Shortage: 0 Level of Development: Present Level of Development Instream Flow Requirements: Timeseries Starting Year Type: 1 Timeseries?: Validation General Model Settings Hydrologic Index: North Yuba Index Target Operating Line: Yuba River Accord Use error checking?: No Use automatic calculations throughout?: No Calculate Water Balance?: No Apply Narrows 1 FERC License?: No Narrows 1 & 2 Flow Split: Current Contract Slate Creek Operations: Historical Flows Groundwater Substitution Transfers: Yes GWS Pumping/Release Pattern: Default Stored Water Transfers: No Drought Level of Protection (For Carryover Storage): 0.99 Maximum Carryover Storage: 600 Delivery Target (For Carryover Storage): 0.5 Maximum Deficiency: 0.5 Maximum September & October Release Above Minimums: 300 Maximum Colgate Release Reduction for Englebright Spill Avoidance: 0.7 Englebright Release Flow Fluctuation Criteria September 15 to October 31 Flow Reduction: 0.55 November 1 to March 31 Maximum Flow Reduction: 0.65 Maximum Daily Flow Reduction: 0.7 Maximum Daily Late Summer Flow Reduction: 200 For the input timeseries data located on the Input-Timeseries tab, all values are identical to the values provided with the YRDP Model and which are used for the base-case. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-17

128 The following Table lists the values used as constraints input on the Input-Constraints tab of the YRDP Model. These are the identical values used for the base-case. Table Input-Constraints Tab Values. Log Cabin and Our House Dam Constraints Our House Release Buffer: 3 cfs Lohman Tunnel Capacity: 860 cfs Log Cabin Release Buffer: 2 cfs Camptonville Tunnel Capacity: 1,100 cfs New Bullards Bar Reservoir Constraints Colgate Max: 3,430 cfs Colgate Turbine Elevation: 565 ft-msl Maximum Storage: 1,000,000 AF Fish Hydro Release Buffer: 2 cfs Flood Pool Buffer: 8,000 AF New Bullards Bar Normal Max Elevation: 1956 ft-msl New Bullards Bar Reservoir Flood Operation Constraints Maximum flow below Dam: 50,000 cfs Maximum flow in Marysville: 120,000 cfs Englebright Reservoir Constraints Narrows 1 Capacity: 730 cfs Narrows 2 Capacity: 3,400 cfs Narrows Max: 0 cfs Narrows 2 Min Release: 900 cfs Narrows Tailwater Elevation: 287 ft-msl Englebright Dam Crest Elevation: 527 ft-msl Englebright Minimum Pool Elevation: 516 ft-msl Target Englebright Storage: 30,947 AF Elevation Trigger for Max Narrows: 523 ft-msl Englebright Area: 810 acres Englebright Spill Avoidance Forecast: 4 Days Englebright Inflow Threshold (for Flow Fluctuation): 500 cfs Carryover Storage Constraints FERC Minimum Pool : 234 TAF Carryover Storage Operation Buffer: 0 TAF Annual Evaporation: 15 TAF YCWA North Yuba River Water Rights YCWA North Yuba Water Right: 800 cfs Maximum SFWP Diversion over 300 cfs Jan-Jul: 35,000 AF Meet All YCWA Water Rights Prior to Diversion?: No SFWP Flow Requirements: Current Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

129 3.1.3 Groundwater Substitution Time Series Groundwater substitution transfers occurred in 2008, 2009 and Table lists the amount of pumping by each Member Unit in these years. In the validation simulations, the groundwater substitution transfer annual volume is input in a table on the Transfers tab. Groundwater pumping for groundwater substitution, which reduces irrigation diversions, is input as a monthly pattern of values that are percentages of the annual transfer volume. Release of the transfer volume from New Bullards Bar Reservoir and which results in increased flows at the Marysville Gage, are input as monthly percentages of the total transfer volume. Table lists the monthly percentages of groundwater substitution transfer pumping and release used in the validation. Table Groundwater Substitution Transfer Pumping by Member Unit for 2008, 2009 and Member Unit 2008 Pumping 2009 Pumping 2010 Pumping Brophy Water District 11,825 26,958 23,925 Browns Valley Water District 4,236 4,834 3,057 Dry Creek Mutual Water Company 8,424 7,739 5,740 Hallwood Irrigation Company 11,321 12,015 8,018 Ramirez Water District 12,081 10,789 4,552 South Yuba Water District 2,103 17,605 13,209 Cordua Irrigation District -- 8, Wheatland Water District -- 11,473 9,660 Total 49,990 99,735 68,161 Table Monthly Pumping and Release Percentages of Annual Groundwater Substitution Volume. Month: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pumping Pattern: Release Pattern: 0% 0% 0% 0% 5% 15% 30% 30% 5% 10% 5% 0% 0% 0% 0% 0% 0% 10% 50% 40% 0% 0% 0% 0% 4.0 Validation Results Model validation simulation results are summarized for the three-year simulation period of water year 2008 to 2010 and the ten-year period of water year 2001 to Detailed results are presented for the three-year simulation, as this simulation period is consistent with Basecase conditions and current practices for operation of the facilities. Summary results for the ten-year simulation are provided where appropriate. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-19

130 4.1 Validation Simulation Summary The three-year validation simulation of water years 2008 through 2010 closely approximates the historical conditions for flow below Project facilities, reservoir storage in New Bullards Bar Reservoir and power generation at both powerhouses. No attempt was made to accurately simulate the historical storage in Englebright Lake except for operations during storms where spills are occurring at Englebright Dam. The YRDP Model faithfully represents storage conditions during spill events and the occurrence of spills at Englebright Dam. 4.2 Validation Simulation Flows below Project Facilities This section provides a summary of resulting flows below project facilities for the validation simulations. In general, the simulation results accurately reflect the historical flows at the various locations. Several non-recurring operations during the three-year period of 2008 to 2010 were not simulated and therefore provide for variation between the simulation and historical record. These historical operations are discussed under the sections where they affect the corresponding flows Our House and Log Cabin Dams The YRDP Model simulates the operations for diversions and releases to meet required FERC license flows below Our House Dam on the Middle Yuba River and Log Cabin Dam on Oregon Creek. Diversions at Our House Dam are made to the Lohman Ridge Tunnel, which conveys flows from the Middle Yuba River to Oregon Creek several hundred feet upstream of Log Cabin Dam. Diversions to the Camptonville Tunnel are made at Log Cabin Dam and are conveyed to New Bullards Bar Reservoir. Figure is a schematic of the streams, dams and diversion tunnels at these locations as well as USGS gage numbers Figure Schematic of Streams, Dams and Tunnels in the Vicinity of Our House and Log Cabin Dams. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

131 Figure is a semi-log graph of mean daily flow at USGS stream gage , which is located immediately downstream of Our House Dam, as well as a graph for modeled mean daily flows for this location. The graph shows that the YRDP Model properly represents the minimum stream flows and spills at this location. Figure Mean Daily Flow at Below Our House Dam (USGS gage ). Figure is a graph of the historical and modeled mean daily flow in the Lohman Ridge Tunnel, measured by USGS gage The modeled and historical flows are almost identical in this plotted scale. Figure Mean Daily Flow at Lohman Ridge Tunnel (USGS gage ). Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-21

132 Figure is a semi-log graph of historical and modeled mean daily flow below Log Cabin Dam on Oregon Creek, measured by USGS gage The figure shows that the modeled operations closely follow historical operations. Flows in each of the three spring periods for the simulation are lower than the historical flow. Diversions from the Middle Yuba River are used to supplement the natural flow in actual operations, when natural flow in Oregon Creek is at or below the required stream flow. The YRDP Model adheres more closely to the FERC license flow requirement than the historical flow, except for times when the natural flow of Oregon Creek is lower than the required flow and there is no inflow from the Lohman Ridge Tunnel. There is no practical mechanism for segregating tunnel flow from natural inflow under actual operations, so releases below the dam include Lohman Ridge Tunnel inflow when the natural flow from Oregon Creek is lower than the required release below the dam. Figure Mean Daily Flow at Below Log Cabin Dam (USGS gage ). Figure is a graph of the historical and modeled mean daily flow in the Camptonville Tunnel, measured by USGS gage The modeled and historical flows are almost identical at the plotted scale. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

133 Figure Mean Daily Flow at Camptonville Tunnel (USGS gage ). Table lists the mean annual flow for the four gage locations described above along with modeled results for the three-year and ten-year simulations. The difference with historical flows and percent differences are also listed. Table Mean Annual Flow at Gage locations at Our House Dam and Log Cabin Dam. Location Historical Modeled Difference % Difference 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year Below Our House Dam Lohman Ridge Tunnel Below Log Cabin Camptonville % 21% (3.5) (20.4) -2% -12% % 9% (4.6) (22.4) -2% -11% Flows below New Bullards Bar Reservoir and Dam Flows below New Bullards Bar Dam consist of releases through three different outlets: the gated spillway, the low level outlet (hollow jet valve) and the Fish Release. The Fish Release is measured by USGS gage The low level outlet and spillway releases do not have corresponding USGS gage measurements. Instead, the low level outlet releases are determined using a YCWA staff gage at a weir just downstream of the dam and the spillway releases are determined by gate opening and water elevation at the dam. These measurements therefore include some amount of unknown error in the reported flows. In the YRDP Model, the fish release and spillway releases are modeled, but the low level outlet is not. Releases that historically have been made through the low level outlet are assumed to be part of the non-spill Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-23

134 releases from the reservoir that would be made through the powerhouse. Typically, releases are made through the low level outlet only when they cannot be made through the new Colgate Powerhouse (e.g., shut-down of the powerhouse for maintenance, or for testing purposes). Figure is a graph of mean daily flows below New Bullards Bar Dam. The historical values are derived from the sum of measured fish release flows, low level outlet releases estimated from a weir and spills estimated from spillway gate opening and water level. The only historical flows in the figure that are above the fish release flow of 5 to 8 cfs and are a result of a spillway release are the flows of more than 100 cfs to over 2,000 cfs in May of 2009 and Increased releases at other times in the historical data are from the low level outlet. Figure Mean Daily Flow below New Bullards Bar Dam (YCWA historical data used) New Colgate Powerhouse Flows New Colgate Powerhouse releases are the major governing point of control for managing storage in New Bullards Bar Reservoir and for meeting downstream demands for instream flow and irrigation diversions. In addition, weekly and monthly volumes of releases are constrained by storage management and downstream demands, but daily and hourly releases are not as constrained because of the ability to fluctuate daily releases to respond to power market demands. The result is daily fluctuations in releases that are not easily simulated with a water balance/operations model. Figure shows the historical and modeled mean daily releases at New Colgate Powerhouse (USGS gage ) for the 2008 to 2010 water years. A seven day moving average trend line of the historical release is also plotted. As seen in the figure, the YRDP Model simulation is quite close to the seven day average of the historical release and Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

135 reasonably follows the daily historical values, but does not capture the day-to-day variation in historical releases. In the figure, the historical values for the October 2, 2008 through December 17, 2008 are zero, as the powerhouse was shut down for this time period. Releases during this period were made through the low level outlet at the dam. Figure Mean Daily New Colgate Powerhouse Release (USGS gage ) with 7 day moving average of historical releases. Many factors affect the day-to-day variation of releases of New Colgate Powerhouse. One of those factors is the value of power during weekdays versus weekends due to variations in market demand. Prior to 2004 when the California energy market was very strained, New Colgate Powerhouse releases were managed to maximize weekday generation and minimize weekend releases. The focus on weekday generation has diminished since the economic downturn and redesign of the California energy market. However, this factor still plays a part in the variation of New Colgate Powerhouse releases in more recent times. Figure is a graph of New Colgate Powerhouse releases for the summer of The graph shows that most of the lower single or two day flows that are below the near term trend of releases occur on weekends and the maximum releases occur on weekdays. As shown in the YRDP Model results, this factor was not modeled for the validation, but the YRDP Model does have this functionality for future simulations. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-25

136 Figure Mean Daily New Colgate Powerhouse Release (USGS gage ) for Summer 2008, with weekend days shaded gray. Table summarizes annual mean daily historical and modeled flow for New Colgate Powerhouse and for New Colgate Powerhouse plus releases from the New Bullards Bar Reservoir low level outlet. Because the powerhouse was shut down for three months in 2008, releases were made from the low level outlet during this time period. Table Annual Mean Release from new Colgate Powerhouse (USGS Gage ). Location New Colgate PH Release plus Low Outlet Historical Modeled Difference % Difference 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 1, , , ,250.2 (57.8) (43.8) -6% -4% 1, , , ,250.2 (9.0) (29.1) -1% -2% Flows below Englebright Dam including Narrows 1 and Narrows 2 Powerhouse Releases Modeled flows below Englebright Dam are significantly influenced by simulation of New Bullards Bar Reservoir as well as downstream instream flow requirements and irrigation demands. Figure shows historical and modeled mean daily flows at the Smartville gage (USGS gage ) located several hundred feet downstream of Englebright Dam and downstream of the Narrows 1 and Narrows 2 Powerhouses. The graph shows that the YRDP Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

137 Model simulates small freshet storms (e.g. February and March of 2008 and March and April of 2009), as well as the summer releases for flow requirements and irrigation diversions and transfers. Figure Mean Daily Flows below Englebright Dam (USGS gage ). Figure Mean Daily Release at Narrows 2 Powerhouse (USGS gage ). Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-27

138 Figure Mean Daily Release at Narrows 1 Powerhouse (USGS gage ). Figure is a plot of the mean daily release from the Narrows 2 Powerhouse and Figure is a plot of the mean daily release from the Narrows 1 Powerhouse. The determination by the operators of how much of the total flow below Englebright Dam to release through the two powerhouses is influenced by: the capacity of the powerhouse; generating unit efficiency at a given flow; physical condition of the facility (such as maintenance outages); and by the decisions to utilize the Narrows 1 Powerhouse to meet energy market requirements. Releases through the Narrows 1 Powerhouse result in energy generation that qualifies for Renewable Portfolio Standard (RPS) credit and revenue. RPS has additional value to PG&E as it helps PG&E to meet its RPS requirements, and therefore is preferred at certain times and under certain energy market conditions. The modeled priority for releases through Narrows 1 versus Narrows 2 Powerhouse is not intended to simulate the full variability of the power market for RPS generation. The modeled priority is for Narrows 1, whenever possible, to acknowledge the RPS value, however this does not always occur in actual operations. The graph of Figure shows that during the summer of 2008, the Narrows 2 Powerhouse was used exclusively for the entire summer, where the model allocates flows to the Narrows 1 Powerhouse for a portion of the total flow below Englebright. The figures also show other times when the actual flow through Narrows 1 Powerhouse is zero when the YRDP Model is allocating flow to this facility. In addition, the flow though the Narrows 1 Powerhouse is less than the maximum powerhouse flow at some times. The utilization of the Narrows 1 Powerhouse at less than capacity at times where there is sufficient needed flow above the capacity is related to mechanical issues at the powerhouse in which it has occurred historically. Table is a summary of annual mean flow of the total flow measured at the Smartville gage (USGS gage ) as well as at the two Powerhouses; Narrows 1 (USGS gage ) and Narrows 2 (USGS gage ). Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

139 Table Annual Mean Flows below Englebright Dam. Yuba County Water Agency Location Historical Modeled Difference % Difference 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year Smartville , , , ,991.8 (54.9) (53.9) -4% -3% (water year 2007 data not available from USGS - YCWA records used) Narrows 2 PH , , , % 21% Narrows 1 PH (207.7) (353.4) -55% -137% Total Daguerre Point Dam Diversions and Flow at Marysville Gage Agricultural irrigation demands within the YCWA service area are met by diversions at or just upstream of Daguerre Point Dam, which utilizes three separate diversion facilities. Diversions to YCWA Member Units Hallwood Irrigation Company, Cordua Irrigation District and Ramirez Water District are made at the Hallwood-Cordua Canal diversion located on the right (north) abutment of Daguerre Point Dam. Diversions to Browns Valley Irrigation District (BVID) are made at the BVID diversion about 0.9 miles upstream of the Dam on the north side of the river. Diversions to Brophy Water District, South Yuba Water District, Dry Creek Mutual Water Company and Wheatland Water District are made at the South Diversion located about 200 yards upstream of the left (south) abutment of the Dam. In the YRDP Model all of these diversions are simulated as one combined diversion at the Dam. Figure shows total historical and modeled mean daily flow for the three diversion points. Figure Mean Daily Total Diversion Flow at Daguerre Point Dam (BVID, Hallwood-Cordua and South Diversion). Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-29

140 The simulation of these diversions for the 2008 through 2010 period uses a synthetic pattern of diversions based on recent years of historical diversion scaled to the total annual diversion volume used in the model. In addition, the diversions are further modified by the effects of groundwater substitution operations, which reduce diversions because of groundwater pumping by farmers for some of the irrigation demand. The pattern of reduced diversion due to groundwater pumping is established in the YRDP Model as an annual series of percentages of the total annual groundwater pumping, and is a single annual series by month. This simplification of groundwater substitution pumping, along with the variation of year-to-year irrigation demands due to weather and other variables, are the reason for differences between historical and modeled results for diversions. Flows at the Marysville Gage (USGS gage ) are shown in Figure As seen in the figure for the months of July through September for 2008 and 2009, the YRDP Model follows the historical flow, indicating a good representation of operations to meet required instream flows at the gage in addition to the groundwater substitution transfer flows that occurred during these years. Storm peaks are also closely simulated in the YRDP Model, as seen in the figure. Figure Mean Daily Flow at Marysville Gage (USGS gage ). Table is a summary of annual mean flows for the total diversion at Daguerre Point Dam and flow at the Marysville Gage. The annual mean flow for the historical total diversions versus the modeled values for both the three-year and the ten-year simulations are very close, suggesting that the total volume of diversion in the model is accurate. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

141 Table Annual Mean Flows for Total Diversions and at Marysville Gage. Location Historical Modeled Difference % Difference 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year Total Diversions (0.68) 0% 0% Marysville , , , , (44.87) % 2% 4.3 Reservoir Storage As described above in Section 1.5.1, target storage in New Bullards Bar Reservoir, and Section 1.5.2, operations at Englebright Lake, the model operations to manage storage at these reservoirs are approximations, and the model uses simplified methods. Downstream demands for instream flows and irrigation diversions control how storage is managed under dry hydrologic conditions. Under wetter conditions, operators have more latitude in the timing of releases and much of the time these releases are influenced by forecasts of future inflow. Other than the use of a five-dayforward looking operation at Englebright Lake for storm freshet management, forecasted inflow is not a part of the YRDP Model simulation for reservoir operations. The main drivers of variance between historical and simulated reservoir storage are: the difference between dry and wet hydrologic conditions; and year-to-year variations due to transfers and irrigation demands. Figure is a plot of historical and modeled New Bullards Bar Reservoir storage for the three-year simulation. Figure Storage in New Bullards Bar Reservoir. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-31

142 As described in Section 1.3.1, the ten-year simulation of water year 2001 through 2010 is intended to show that the YRDP Model provides a reasonably accurate representation of storage and flows across a wide range of hydrology and for a long simulation period despite historicallyunique operational events for which there has been no attempt to simulate. Figure is a plot of storage in New Bullards Bar Reservoir for the ten-year simulation period. The modeled storage does not reach the low storage seen historically at the end of water years 2002 and 2004, mainly because of additional releases of water for power generation in spring and early summer to respond to critical power shortages in the California power market. The modeled lower storage in late 2006 through 2007 is a result of a transfer release that was made in 2006, which has not been modeled. Figure Storage in New Bullards Bar Reservoir for Water Year 2001 through Storage in Englebright Lake is shown in Figure The figure shows that historic Englebright storage fluctuates extensively, but only within a very narrow range of about 4,000 to 5,000 acreft in the summer and fall, however storage increases above that range when storm flows enter the reservoir. Because no attempt is made to simulate the day-to-day variations in releases from Colgate Powerhouse due to energy market demands and PG&E s scheduling of power at that particular powerhouse, the YRDP Model does not fluctuate Englebright Lake storage unless it is to manage a storm inflow event. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

143 Figure Storage in Englebright Lake. 4.4 Powerhouse Generation As described in the Modeling Report, power generation for the New Colgate and Narrows 2 Powerhouses is derived from empirical data to fit generation to flow and head from the historical records of the past 10 years. Therefore, variance between the historical generation and modeled generation for these two powerhouses is primarily due to differences in flow and storage (elevation) between the historical and modeled conditions. Figure is a graph of daily power generation at New Colgate Powerhouse. Comparing the power generation graph to the graph of releases from New Colgate Powerhouse, the variance between historical and modeled values for generation and flow are similar. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-33

144 Figure Power Generation at Colgate Powerhouse. Figure is a plot of daily power generation at Narrows 2 Powerhouse. As with the New Colgate Powerhouse plot, the Narrows 2 Powerhouse generation variance between the historical and modeled data is mostly a result of variance in flow between these two conditions. Figure Power Generation at the Narrows 2 Powerhouse. Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

145 Table summarizes annual mean generation at the New Colgate and Narrows 2 Powerhouses for the three-year and ten-year simulations. Table Annual Mean Daily Powerhouse Generation (MWH). Location Historical Modeled Difference % Difference 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year 3 Year 10 Year Colgate 2, , , ,858.6 (162.7) (51.8) -7% -2% Narrows % 26% 5.0 Validation Data Sets The validation data sets consist of a validation input file that is an HEC.DSS format file and a validation output file that is also in the HEC.DSS format. The output file includes the results of the three-year simulation and the ten-year simulation. For the three-year validation simulation results of WY 2008 through 2010, the F Part of these output records is in the file labeled, VAL3. For the ten-year validation simulation results of WY 2001 through 2010, the F Part of these output records in the file is labeled VAL10. Model Validation Report Technical Memorandum 2-2 Attachment 2-2B November , Yuba County Water Agency Page B-35

146 Page Left Blank Attachment 2-2B Technical Memorandum 2-2 Model Validation Report Page B , Yuba County Water Agency November 2012

147 Technical Memorandum 2-2 Water Balance/Operations Model Attachment 2-2C Base Case Scenario Report November , Yuba County Water Agency All Rights Reserved

148

149 Table of Contents Section No. Description Page No. 1.0 Introduction General Assumptions Period of Record for Simulation Starting Storage Regulatory Requirements and Agreements Instream Flow Requirements FERC Licenses Lower Yuba River Accord PG&E Power Purchase Contract Flood Management Agricultural Irrigation Demands Annual Demands Daily Pattern Shortages Project Hydrology Sources of Inflows Historical Inflows Synthetic Inflows Upstream Project Assumptions Slate Creek Middle Yuba River South Yuba River Other Project Operations New Bullards Bar Reservoir Target Operating Line Operations New Bullards Bar Reservoir Carryover Storage Operations New Colgate Powerhouse Operations Englebright Reservoir Operations Reservoir Levels Fluctuation for Power Generation Division of Flow between Narrows 1 and 2 Powerhouses Groundwater Substitution Transfers Summary of Base Case Scenario Modeling Assumptions Base Case Scenario Output Our House Diversion Dam Releases Lohman Ridge Tunnel Flow Log Cabin Diversion Dam Releases...29 Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page TOC-i

150 7.4 Camptonville Tunnel Flow New Bullards Bar Reservoir Storage New Bullards Bar Reservoir Spill New Bullards Bar Minimum Flow Hydro Releases New Colgate Powerhouse Releases New Colgate Powerhouse Generation Englebright Reservoir Elevation Narrows 1 Powerhouse Releases Narrows 1 Powerhouse Generation Narrows 2 Powerhouse Releases Narrows 2 Powerhouse Generation Narrows 2 Bypass Englebright Reservoir Spill Smartville Flow Agricultural Deliveries Marysville Flow...44 List of Figures Figure No. Description Page No Yuba River Accord North Yuba Index....C Historical and synthetic inflows to the YRDPM....C Exceedance probability of simulated mean daily middle Yuba River Flow below Our House Diversion Dam for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily flow in the Lohman Ridge Tunnel for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily flow in Oregon Creek below Log Cabin Diversion Dam for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Camptonville Tunnel flow for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily New Bullards Bar Reservoir storage for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily New Bullards Bar Reservoir spill for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily new Bullards Bar Reservoir release through the Fish Hydro for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily New Colgate Powerhouse release for the Base Case scenario (WY )....C-34 Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page TOC-ii 2012, Yuba County Water Agency November 2012

151 List of Figures (continued) Figure No. Description Page No Exceedance probability of simulated mean daily New Colgate Powerhouse generation for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Englebright Reservoir water surface elevation for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily releases from PG&E s Narrows 1 Powerhouse for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Narrows 1 Powerhouse generation for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily releases from the Narrows 2 Powerhouse for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Narrows 2 Powerhouse generation for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily releases from the Narrows 2 Bypass for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily releases from the Narrows 2 Bypass for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Yuba River flow at Smartville for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily agricultural deliveries from Daguerre Point Dam for the Base Case scenario (WY )....C Exceedance probability of simulated mean daily Yuba River flow at Marysville for the Base Case scenario (WY )....C-44 List of Tables Table No. Description Page No Narrows Project flow requirements in the Yuba River at Smartville....C Lower Yuba River Accord flow schedules....c Storage criteria for New Bullards Bar Reservoir under the 1966 PG&E Power Purchase Contract and 2008 Power Purchase Contract Amendment....C Forecasted available water thresholds used to determine appropriate storage to be used for Power Purchase Agreement Critical Line...C New Bullards Bar Reservoir flood storage space allocation....c Land use information for the YCWA Member Units....C Applied water rates for Yuba County agriculture....c Synthetic annual applied water demand for YCWA Member Units....C USGS gages used to determine historical inflows to the YRDPM....C Areas and average annual precipitation for YRDPM subbasins....c Base Case New Bullards Bar Reservoir target operating line and buffers (TAF)...C-19 Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page TOC-iii

152 List of Tables (continued) Table No. Description Page No Division of Englebright Reservoir releases by flow rate (cfs)....c Groundwater substitution transfer monthly pumping and release patterns....c Base Case scenario modeling assumptions...c Simulated monthly average Middle Yuba River flow below Our House Diversion Dam (WY )....C Simulated monthly average flow in the Lohman Ridge Tunnel (WY )....C Simulated monthly average Oregon Creek flow below Log Cabin Diversion Dam (WY )....C Simulated monthly average Camptonville Tunnel flow. (WY )....C Simulated monthly average New Bullards Bar Reservoir storage. (WY )....C Simulated monthly average New Bullards Bar Reservoir spill (WY )....C Simulated Monthly Average New Bullards Bar Reservoir Release through the Fish Hydro. (WY )....C Simulated monthly average New Colgate Powerhouse release (WY )....C Simulated monthly average New Colgate Powerhouse generation (WY )....C Simulated monthly average Englebright Reservoir water surface elevation (WY )....C Simulated monthly average Narrows 1 Powerhouse releases (WY )....C Simulated monthly average Narrows 1 Powerhouse generation (WY )....C Simulated monthly average Narrows 2 Powerhouse releases (WY )....C Simulated monthly average Narrows 2 Powerhouse generation (WY )....C Simulated monthly average Narrows 2 bypass releases (WY )....C Simulated monthly average Englebright Reservoir spill (WY )....C Simulated monthly average Yuba River flow at Smartville (WY )....C Simulated monthly average agricultural delivery from Daguerre Point Dam (WY )....C Simulated monthly average Yuba River flow at Marysville (WY )....C-44 Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page TOC-iv 2012, Yuba County Water Agency November 2012

153 1.0 Introduction This report describes the Base Case scenario (Base Case) for Yuba County Water Agency s (YCWA) (Project or YRDP), Federal Energy Regulatory Commission (FERC) Project 2246, as simulated using the Model (YRDPM). The Base Case is intended to represent conditions as they currently exist, with the current rules, regulations, water supply demands, and operational practices. This report provides a description of the general assumptions, regulatory requirements and agreements, water supply demands, and other project considerations included within the Base Case. The report also includes a tabular summary of these assumptions, and a discussion of selected model output. 1.1 General Assumptions There are several assumptions included in the Base Case not having to do with specifics of the Project, but regarding the simulation of the system. This section describes those general assumptions Period of Record for Simulation The Base Case scenario is simulated for the 41-year period of October 1, 1969 through September 30, This period essentially covers the operational period of the Project. Throughout this report, this will be referred to as the period of record Starting Storage The historical end-of-day storage for New Bullards Bar Reservoir on September 30, 1969 of 551,051 acre-feet (ac-ft) is used for the starting New Bullards Bar Reservoir storage for the period of record. This was the first year of filling the reservoir and provides a reasonable representation of reservoir storage given the preceding year s hydrology. Englebright Reservoir s storage is not assumed to vary due to normal operations; starting storage was set at the daily target storage of 30,947 ac-ft, or at 519 feet above mean sea level (ft-msl). 2.0 Regulatory Requirements and Agreements Many of the operational objectives driving the Project are contained in requirements or agreements. This section describes operational objectives affecting the Base Case memorialized in either a regulatory requirement or in an operational agreement. 2.1 Instream Flow Requirements The Project is subject to several minimum instream flow requirements throughout the system. Flow requirements have historically been prescribed by FERC licenses, the State Water Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-1

154 Resources Control Board (SWRCB) Revised Decision 1644 (RD-1644), and the Lower Yuba River Accord (Yuba Accord). This section describes the flow requirements included in the Base Case scenario FERC Licenses Since its construction, the primary objective driving the Project s operations has been the initial FERC license. The Base Case reflects operations for the Project s initial FERC license. In addition, the Project is affected by several other upstream projects operating under separate FERC licenses, namely those owned by Pacific Gas and Electric Company (PG&E) for the Narrows Project on the Yuba River and the Drum-Spaulding Project on the South Yuba River, South Feather Water and Power Agency (SFWPA) for the South Feather Project on Slate Creek, and the Nevada Irrigation District (NID) for the Yuba-Bear Project on the Middle Yuba River. This section describes the various FERC licenses affecting Project operations PG&E Narrows Project FERC Project 1403 FERC issued a license under the Federal Power Act to PG&E for the Narrows Project, FERC Project 1403, on February 11, 1993 (FERC 1993). The license includes minimum instream flow requirements in the Yuba River below the Narrows 1 Powerhouse. The license recognizes the Project would be undergoing a relicensing process as well, and that the Power Purchase Agreement between YCWA and PG&E would expire when the Project license expires. In the interim, the Narrows Project license requires PG&E to supplement releases from the project to ensure the flow requirements in the Yuba River below Englebright Dam at Smartville, as described in Table 2.1-1, are met. Table Narrows Project flow requirements in the Yuba River at Smartville. Date Flow Requirement (cfs) October 1 to March April 1 to April 30 1,000 May 1 to May 31 2,000 June 1 to June 30 1,500 July 1 to September cfs = cubic feet per second The flows in Table are not required when either of the following conditions is met: The total annual (by water year) volume of water released to meet the flow schedules in Table exceeds 45,000 ac-ft. Englebright Reservoir water surface is less than 514 ft-msl or PG&E may not dispatch storage in New Bullards Bar Reservoir under the Power Purchase Agreement between YCWA and PG&E as discussed below. In addition to its FERC License, PG&E holds an appropriative water right license (License 6388, with a permit date of September 21, 1936), which confirms PG&E s right to divert Yuba River water for power at the Narrows 1 Powerhouse. This water right license confirms PG&E s right Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

155 to directly divert 700 cfs year around and 45,000 ac-ft per year to storage between October 1 and March SFWPA South Feather Power Project FERC Project 2088 FERC issued a license under the Federal Power Act to SFWPA for Project 2088 on April 1, 1959 for the operation of the South Feather Power Project (SFP). The initial license expired on March 31, 2009 and SFWPA filed for a new license in March Since the SFP receives water diverted from Slate Creek (which is a tributary to the North Yuba River) at the Slate Creek Diversion Dam, operations of the SFP affect the YRDP by affecting the volume of water diverted from the Yuba River watershed NID Yuba-Bear Project FERC Project 2266 and PG&E Drum-Spaulding Project FERC Project 2310 FERC issued licenses for Projects 2266 (Yuba-Bear Project) and 2310 (Drum-Spaulding Project) to NID and PG&E, respectively, for the period of May 1, 1963 through April 30, The projects are each currently undergoing their respective relicensing processes. Since operations of the Yuba-Bear and Drum-Spaulding projects affect flows on the Middle and South Yuba rivers, respectively, they have an effect on the YRDP YCWA FERC Project 2246 FERC originally issued a license under the Federal Power Act for the Project on May 16, 1963 (FERC 1963). On May 6, 1966, FERC issued an order amending this license. The amended license contains release and instream flow requirements similar to the 1965 agreement between YCWA and California Department of Fish and Game (CDFG). YCWA is obligated to operate the YRDP in such a way as to meet minimum instream flows throughout the year below New Bullards Bar Dam, Englebright Dam, and Daguerre Point Dam, as described below. Minimum Releases Below New Bullards Bar Dam The required minimum release to the North Yuba River from New Bullards Bar Reservoir is 5 cfs year-round. YCWA typically meets this requirement by releases from the bottom outlet of New Bullards Bar Dam through the Minimum Flow Powerhouse. Minimum Flow Requirements Below Englebright Dam YCWA s 1966 FERC license specifies that, with the exception of flood control operations and release of uncontrolled inflows from tributary streams, releases from Englebright Dam are to be continuous and uniform. Scheduled releases must be within the limits prescribed below: 600 to 1,050 cfs, from October 16 to October to 700 cfs, from November 1 to November to 1,400 cfs, from December 1 to December 31 Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-3

156 1,000 to 1,850 cfs, from January 1 to January cfs minimum, from January 16 to March 31 Minimum Flow Requirements Below Daguerre Point Dam Minimum flows as measured over the crest of Daguerre Point Dam and in the fish passage at that dam are as follows: 245 cfs, from January 1 to June cfs, from July 1 to September cfs, from October 1 to December 31 Required minimum water releases for fishery resources are subject to reductions in critical water years, which are defined as those water years for which the April 1 forecast by the California Department of Water Resources (DWR) predicts that the annual unimpaired flow in the Yuba River at Smartville will be 50 percent or less of normal. Water release curtailments for critical water years are release reductions of 15, 20, and 30 percent when Yuba River unimpaired flow forecasts are 50, 45, and 40 percent, respectively, or less of normal. The critical water year provision is effective from the time of the forecast until April 1 of the following year. However, in no event may these minimum flows be reduced to less than 70 cfs. Minimum Flow Requirements Below Our House Diversion Dam Minimum flows, as measured immediately below Our House Diversion Dam, for the maintenance of fish life in the Middle Yuba River, are as follows: 50 cfs or the natural inflow, whichever is less, from April 15 through June cfs or the natural flow, whichever is less, from June 16 through April 14 Minimum Flow Requirements Below Log Cabin Diversion Dam Minimum flows, as measured immediately below Log Cabin Diversion Dam, for the maintenance of fish life in Oregon Creek, are as follows: 12 cfs or the natural inflow, whichever is less, from April 15 through June 15 8 cfs or the natural inflow, whichever is less, from June 16 through April 14 Flow Fluctuation and Reductions (Ramping Criteria) YCWA operates the Project to meet specific criteria for flow fluctuations as measured at the Smartville Gage. Flow fluctuation criteria are specified in the 1966 FERC License, and in SWRCB RD On November 22, 2005, FERC issued an order amending YCWA s license for the Project that contains flow fluctuation criteria similar to those specified in RD The 2005 amended license is the controlling requirement for operation of the Project. The amended license specifies that the YRDP will be operated according to the following requirements: Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

157 With the exception of emergencies, releases required by U.S. Army Crops for Engineers flood control criteria, releases required to maintain a flood control buffer or for other flood control purposes, bypasses of uncontrolled flows into Englebright Reservoir, uncontrolled spilling, or uncontrolled flows of tributary streams downstream of Englebright Dam, Licensee shall make reasonable efforts to operate New Bullards Bar Reservoir and Englebright Reservoir to avoid fluctuations in the flow of the lower Yuba River downstream of Englebright Dam, and daily changes in project operations affecting releases or bypasses of flow from Englebright Dam shall be continuously measured at the USGS gage at Smartville, and shall be made in accordance with the following conditions: i. Project releases or bypasses that increase streamflow downstream of Englebright Dam shall not exceed a rate of change of more than 500 cfs per hour. ii. Project releases or bypasses that reduce streamflow downstream of Englebright dam shall be gradual and, over the course of any 24-hour period, shall not be reduced below 70 percent of the prior day s average flow release or bypass flow. iii. Once the daily project release or bypass level is achieved, fluctuations in the streamflow level downstream of Englebright Dam due to changes in project operations shall not vary up or down by more than 15 percent of the average daily flow. iv. During the period from September 15 to October 31, the licensee shall not reduce the flow downstream of Englebright Dam to less than 55 percent of the maximum five-day average release or bypass level that has occurred during that September 15 to October 31 period or the minimum streamflow requirement that would otherwise apply, whichever is greater. v. During the period from November 1 to March 31, the licensee shall not reduce the flow downstream of Englebright Dam to less than the minimum streamflow release or bypass established under (iv) above; or 65 percent of the maximum five-day average flow release or bypass that has occurred during that November 1 to March 31 period; or the minimum streamflow requirement that would otherwise apply, whichever is greater Lower Yuba River Accord In 2005, YCWA and 16 other interested parties signed memoranda of understanding that specify the terms of the Yuba Accord, a comprehensive, consensus-based program to protect and enhance aquatic habitat in the Yuba River downstream of the U.S. Army Corps of Engineers (USACE) Englebright Dam and to resolve disputes associated with RD Following environmental review, YCWA and the parties executed the following four agreements in 2007, which together comprise the Yuba Accord: The Lower Yuba River Fisheries Agreement, which specifies the Yuba Accord s lower Yuba River minimum streamflows and creates a detailed fisheries monitoring and evaluation program The Water Purchase Agreement, under which DWR purchases water, some of which is provided by the Yuba Accord s minimum streamflows, from Licensee for CALFED s Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-5

158 Environmental Water Account and State Water Project and Central Valley Project contractors The Conjunctive Use Agreements with seven of YCWA s Member Units, which specify the terms of the Yuba Accord s groundwater conjunctive use program Amendments to the 1966 Power Purchase Contract between YCWA and PG&E Together, this package of agreements provides more water for instream flows and greater reliability for both instream and consumptive uses than would have been possible without the agreements. YCWA has been operating the Project in conformance with the Yuba Accord since The 2006, 2007 and early 2008 operations were under one-year pilot programs that were approved by the SWRCB. On May 20, 2008, SWRCB adopted its Corrected Order WR , which approved the long-term amendments to YCWA s water right permits that were necessary so that YCWA may continue to implement the Yuba Accord. The Yuba Accord includes a specific set of flow schedules for the lower Yuba River. The flow schedule that is in effect at any particular time is determined by the North Yuba Index (NYI), a hydrologic index that was developed as a part of the Yuba Accord. The flow schedules are listed in Table The NYI is shown in Figure Table Lower Yuba River Accord flow schedules. Schedule Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total Annual Volume (ac-ft) MARYSVILLE GAGE 1 (cfs) ,000 1,000 2,000 2,000 1,500 1, , ,000 1, , , , , ,155 SMARTVILLE GAGE 1 (cfs) A B ac-ft = acre-feet, cfs = cubic feet per second 1` Marysville and Smartville gage flows represent average daily flows for the specified time period. Actual flows may vary from the indicated flows according to established criteria. 2 Marysville Gage Schedule 6 flows do not include an additional 30,000 ac-ft available from groundwater substitution to be allocated according to established criteria. 3 Smartville Gage Schedule A is used with Marysville Schedules 1, 2, 3, and 4. 4 Smartville Gage Schedule B is used with Marysville Schedules 5 and 6. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

159 Flow Schedule Year Types based on the North Yuba Index For Establishing Required Flows in the Lower Yuba River Accord Fisheries Agreement The water year hydrologic classification for the Yuba River to determine the flow requirements of Yuba County Water Agency s water right permits shall be based on the North Yuba Index. Determinations of a year s flow schedule year type shall be made in February, March, April, and May and for any subsequent updates. Flow Schedule Year Type North Yuba Index Thousand Acre-Feet (TAF) Schedule 1... Equal to or greater than 1400 Schedule 2... Equal to or greater than 1040 and less than 1400 Schedule 3... Equal to or greater than 920 and less than 1040 Schedule 4... Equal to or greater than 820 and less than 920 Schedule 5... Equal to or greater than 693 and less than 820 Schedule 6... Equal to or greater than 500 and less than 693 Conference Year... Less than 500 Figure Yuba River Accord North Yuba Index. Schedule 1 Schedule 2 Schedule 3 Schedule 4 Schedule 5 Schedule 6 Conference During Conference Years (i.e., years when the North Yuba Index is less than 500,000 ac-ft, which are expected to occur approximately 1 percent of the time), YCWA is required to: Maintain minimum instream flows in the lower Yuba River at the levels specified in Article 33 of YCWA s existing FERC license without the reductions authorized by Subsections (c) and (d) of that article Release any supplemental flows recommended by the Lower Yuba Accord River Management Team Planning Group and approved by the SWRCB s Deputy Director for Water Rights or, if no such recommended flows are effective by April 11 of such a Conference Year, then to release any supplemental flow orders by the SWRCB, after a hearing under California Code of Regulations, Title 23, Section 767 Limit total diversions at Daguerre Point Dam to 250,000 ac-ft. For additional information regarding the Yuba Accord, refer to ycwa.com/projects/detail/ PG&E Power Purchase Contract YCWA originally executed a Power Purchase Contract with PG&E on May 13, 1966 (1966 Agreement), and amended it as part of the implementation of the Yuba River Accord in 2008 (2008 Amendment). The Power Purchase Contract, which originally allowed financing the Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-7

160 construction of the Project and, as amended, provides for cooperative operation of the Project to meet the objectives of the Yuba River Accord, specifies conditions of PG&E's power purchase from YCWA and PG&E's rights to require releases of water from New Bullards Bar Reservoir for power production. Power Purchase Contract Appendix C, Subsection C-2.A.(b), Water for Power and Irrigation, details the monthly storage criteria and monthly power quotas. The maximum end-of-month storage amount (the "Critical Line") is described in paragraph (1): When it appears that storage by the end of any month will exceed the critical amount for such month listed in Appendix D, project power plants shall be operated, unless otherwise agreed, to reduce the storage on hand by the end of such month to the amount specified in Appendix D but at rates not to exceed the amount required for full capability operation except when greater releases are needed by reason of flood control requirements Compliance with this criterion requires releases of up to 3,400 cfs at New Colgate Powerhouse to bring the end-of-month storage at or below the amounts listed in Table 2.2-1, which is the critical storage at end of month in Yuba s New Bullards Bar Reservoir of Table 2.1 of the 2008 Amendment. Table Storage criteria for New Bullards Bar Reservoir under the 1966 PG&E Power Purchase Contract and 2008 Power Purchase Contract Amendment. Storage (TAF) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 1966 Agreement Amendment TAF = thousand acre-feet Source: New Bullards Bar Reservoir Operations Amendment to the Yuba County Water Agency Power Purchase Contract The determination of whether to use the 1966 Agreement storage target or the 2008 Amendment storage target is determined by PG&E based on its calculation of forecasted available water, which is calculated at the beginning of the month after snow survey results are available for the months of February, March, April, and May each year. If the forecasted available water is greater than the monthly levels listed in Table 2.2-2, the target storage from the 1966 Agreement is used for that month. Otherwise, the target storage from the 2008 Amendment is used as the Critical Line described above. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

161 Table Forecasted available water thresholds used to determine appropriate storage to be used for Power Purchase Agreement Critical Line Month Forecasted Available Water(TAF) February 1,690 Marcy 1,830 April 1,320 May 1,020 TAF = thousand acre-feet Source: New Bullards Bar Reservoir Operations Amendment to the Yuba County Water Agency Power Purchase Contract Additionally, the contract also provides that the Narrows II Powerhouse shall be operated in a manner consistent with the foregoing water release requirements. 2.3 Flood Management New Bullards Bar Reservoir must be operated from September 16 to May 31 to comply with Part 208 Flood Control Regulations, New Bullards Bar Dam and Reservoir, North Yuba River, California, pursuant to Section 7 of the Flood Control Act of 1944 (58 Stat. 890). Under the contract between the United States and YCWA that was entered into on May 9, 1966, YCWA agreed to reserve 170,000 ac-ft of storage space in New Bullards Bar Reservoir for flood management in accordance with the rules and regulations enumerated in Appendix A of the Report on Reservoir Regulation for Flood Control (USACE 1972). The seasonal flood storage space allocation schedule is presented in Table Table New Bullards Bar Reservoir flood storage space allocation. Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Storage Allocation (TAF) TAF = thousand acre-feet Additionally, to avoid having dramatic fluctuations in releases, an 8,000 ac-ft buffer on the flood reservation space is included in modeling to smooth operations, however this buffer is not used in actual practice; buffers used in real-world operations are dependant on watershed conditions and other factors, and can vary from year to year. Once reservoir storage encroaches into the flood reservation space, the YRDPM will make releases up to the maximum spillway capacity, depending on reservoir elevation, to evacuate New Bullards Bar Reservoir storage from the flood reservation and buffer space. However, when storage is increasing, the YRDPM will not make releases above New Colgate Powerhouse capacity until storage encroaches into the flood reservation space. In addition to reservation of flood control space in New Bullards Bar Reservoir, the flood management regulations include rules governing ramping rates as well as target maximum flows in the Yuba River and the Feather River below the confluence with the Yuba River. New Bullards Bar Reservoir is operated for the following maximum flows: Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-9

162 50,000 cfs on the North Yuba River below New Bullards Bar Dam 120,000 cfs on the Yuba River at Marysville 300,000 cfs on the Feather River below the Yuba River 320,000 cfs on the Feather River below the Bear River Without any representation of the Feather River, the Base Case does not include any consideration for flows below Marysville. YCWA also coordinates operations with PG&E s Narrows 1 Powerhouse at Englebright Dam to utilize storage in USACE s Englebright Reservoir to capture winter storm freshets and reduce storm flows on the lower Yuba River. The Base Case includes a four-day look ahead function, where the YRDPM makes sure Englebright Reservoir inflows (excluding New Bullards Bar Reservoir releases) do not exceed the combined capacity of the Narrows 1 and 2 Powerhouses. If inflows exceed the Narrows 1 and 2 Powerhouses capacity, New Colgate Powerhouse releases are reduced by up to 30 percent to reduce storage in Englebright Reservoir. Changes in releases from Narrows 1 and 2 Powerhouses are not as part of this initial action; however, if reductions in releases from the New Colgate Powerhouse are insufficient to prevent increases in storage at Englebright Reservoir, the YRDPM increases releases from the Narrows 1 and 2 Powerhouses to their combined maximum capacity once Englebright Reservoir water surface elevation reaches 523 ft-msl. If storage continues to increase, Englebright Reservoir will begin to spill when its water surface elevation reaches 527 ft-msl. The YRDPM ensures Narrows 1 and 2 Powerhouses release at their maximum capacity any time Englebright Reservoir spills. 3.0 Agricultural Irrigation Demands One of the Project s primary purposes is to provide water supply to agricultural irrigators in Yuba County. These deliveries occur from three diversions on the lower Yuba River near Daguerre Point Dam. For modeling purposes, these three diversions are aggregated into a single data timeseries. This section describes the assumptions used to develop the agricultural water supply demands for the Base Case scenario. For a detailed description of the methodology used to compute the agricultural water supply demand, see Appendix B, Diversion Demand Development Report. 3.1 Annual Demands The DWR Land and Water Use Program collects land use data for the entire State of California every few years, and publishes it as geographic information system databases. The most recent survey of Yuba County was conducted in 2005; the land use data is currently provisional, and has not been made publicly available. For the purposes of this analysis, DWR provided YCWA with the most up-to-date databases. Figure shows the 2005 land use data from DWR for the eight YCWA Member Units. The land use for each of the Member Units was extracted from the DWR database and is summarized in Table Land use data listed for Wheatland Water District (WWD) included Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

163 in Table only represents land served by surface water from the Wheatland Project as of July Table Land use information for the YCWA Member Units. Member Unit Acreage (acres) Land Use Type BWD BVID CID DCMWC HIC RWD SYWD WWD Alfalfa Almonds Bare Soil Corn Grain Native Vegetation 3,454 38,514 1, , ,481 3,510 Open Water 122 1, Other Deciduous 1, ,649 1, ,491 Other Field Other Truck Pasture 1,711 3, , , Pistachios Rice 8,873 2,754 8, ,648 3,882 4, Sub-Tropical Urban 1,044 2, , Vineyards Total 17,197 50,183 11,641 4,100 11,981 5,169 9,632 6,762 BWD = Brophy Water District BVID = Browns Valley Irrigation District CID = Cordua Irrigation District DCMWC = Dry Creek Mutual Water Company HIC = Hallwood Irrigation Company RWD = Ramirez Water District SYWD = South Yuba Water District WWD = Wheatland Water District -- = not applicable Source: DWR Land and Water Use Program 2005 Land Use Survey The DWR Land and Water Use Program publishes applied water rates by county based on annual surveys for each of the crop types included in Table The most recent surveys were conducted in 1998, 1999, 2000, and and 1999 were relatively wet years, 2000 was an above normal year, and 2001 was a dry year. The Yuba County-applied water rates for a wet year, 1999, and a dry year, 2001, for the 19 crops are detailed in Table was chosen over 1998 since 1998 was abnormally wet, and was not representative of a typical wet year was chosen since it is the only dry year for which DWR has published applied water rates. As would be expected, dry years require additional irrigation compared to wet years; precipitation can substantially reduce the required volume of applied water if it occurs at a beneficial time. Table Applied water rates for Yuba County agriculture. Land Use Applied Water Rate (ac-ft/ac/year) 1999 (Wet Year) (Dry Year) 1 Alfalfa Almonds Bare Soil 2 2 Corn Grain Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-11

164 Table (continued) Land Use Applied Water Rate (ac-ft/ac/year) 1999 (Wet Year) (Dry Year) 1 Native Vegetation 2 2 Open Water 2 2 Other Deciduous Other Field Other Truck Pasture Pistachios Rice Safflower Sub-Tropical Urban 2 2 Vineyards 3 3 ac-ft/ac/year = acre-feet per acre per year, YRI = Yuba River Index, SVI = Sacramento Valley Index 1 Wet and Dry year classifications are based on both the YRI and SVI. 2 No applied water rates are included for Bare Soil, Native Vegetation, Open Water, or Urban land uses since they are not considered irrigated lands. 3 No applied water rate is included for Vineyard since there is very little land in Yuba County planted with vineyards so DWR did not include an applied water rate. Source: DWR Land and Water Use Program 1999 and 2001 Applied Water rate Survey Using a combination of data from Tables and 3.1-2, and assuming a 10 percent loss factor due to canal seepage or canal evaporation, and a tailwater recycle rate of 5 percent in the northern part of the basin and 10 percent for the southern portion, an annual applied water volume for each Member Unit was computed. Table shows the computed synthetic annual applied water demand for each district for a dry year and a wet year. Table Synthetic annual applied water demand for YCWA Member Units. YCWA Member Unit Synthetic Annual Demand (ac-ft) Present Level Development Wet Year Dry Year Brophy Water District 67,187 70,413 Browns Valley Irrigation District 34,723 36,383 Cordua Irrigation District 55,494 58,398 Dry Creek Mutual Water Company 15,552 16,034 Hallwood Irrigation Company 47,252 49,394 Ramirez Water District 24,295 25,596 South Yuba Water District 34,860 36,725 Wheatland Water District 11,835 12,139 Total 291, ,081 ac-ft = acre-feet Senior water rights of downstream water purveyors such as Browns Valley Irrigation District, Cordua Irrigation District, and Hallwood Irrigation Company are reflected in the representation of the irrigation diversions from Daguerre Point Dam. Water rights of riparian users from the Yuba River below Englebright Dam have been included in previous modeling of agricultural demands, but are not included in this version since the majority of those diversions no longer occur. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

165 3.2 Daily Pattern To convert the annual volumes previously described into a daily timeseries, historical daily average deliveries, as reported by YCWA, for 2003 through 2007 for each Member Unit were used to develop a pattern of deliveries. The time period of 2003 through 2007 was used since it is relatively recent and land use for those years is likely to be similar to both the year of the survey (2005) and for the FERC relicensing process. Also, with the exception of WWD, each Member Unit had been receiving YCWA surface water deliveries long enough to ensure construction of most necessary infrastructure. While no historical YCWA surface water diversion records were available for WWD, as long as there are no dramatic changes in land use or irrigation practices, the process used to determine other Member Units diversion demand should be valid for WWD. Since the daily distribution of deliveries is dependant upon land use and irrigation practices, each Member Unit s historical deliveries were used to determine the synthetic delivery pattern, rather than applying a generalized delivery pattern. No historical daily deliveries were available for WWD, so historical deliveries to Dry Creek Mutual Water Company were used as a surrogate since the two districts have similar land use distribution. Water rights limit deliveries between January and April, but historical delivery records often reflect some minimal flow in this time, likely due to accretions to the canals through the Goldfields or from precipitation rather than an active diversion from the Yuba River. Since the delivery records reflect these passive diversions, this analysis includes them as well, since it is possible accretions from the Yuba River could affect flows in the lower Yuba River. After adding up the total volume of delivery for each Member Unit for each water year from 2003 through 2007, the daily distribution of the annual volume was computed as a percentage to determine the pattern of delivery. Daily patterns for 2004 and 2007 were averaged to compute a daily dry year delivery pattern, and daily patterns from 2005 and 2006 were averaged to compute a daily wet year delivery pattern. Applying the dry and wet year delivery patterns to the annual wet and dry year delivery volumes computed based on land use and applied water rates resulted in wet and dry year daily delivery timeseries for each Member Unit consistent with historical irrigation and with a land use based annual demand. 3.3 Shortages Reductions in deliveries are applied if the YRDPM predicts that the end-of-september storage in New Bullards Bar Reservoir is less than the Carryover Storage Target, as described in Section 5.2. If the end-of-september storage is forecasted to be below the Carryover Storage Target, an equivalent volume to the storage shortage is applied to deliveries. Since a reduction in deliveries would not affect New Bullards Bar Reservoir storage at times when the Smartville flow requirement is controlling Englebright Reservoir releases, the shortage is only applied to periods when the Marysville flow requirement is controlling Englebright Reservoir operations. The volume of storage shortage is applied evenly to periods of Marysville control prior to September 30. This reduction is computed as a percentage and is applied on a calendar year basis. The Base Case assumes a maximum shortage for purposes of meeting the New Bullards Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-13

166 Bar Reservoir end-of-september Carryover Storage Target of 50 percent. The 50 percent maximum shortage is consistent with terms of water supply contracts and senior water rights. If the end-of-september storage would be below the Carryover Storage Target after a 50 percent shortage is applied, New Bullards Bar Reservoir storage is allowed to continue to drop until it reaches the minimum pool. At that point, all inflows are released up to the controlling flow on the lower Yuba River, and agricultural diversions can occur only after minimum flow requirements have been met. 4.0 Project Hydrology The YRDPM uses historical inflows from the North Yuba River, Slate Creek, Middle Yuba River, South Yuba River, Oregon Creek, and Deer Creek, along with synthetic accretions for the entire period of record. The period of record for project inflows was selected for several reasons including the following: There is available gage data for the historical inflows for all gages for this period of record. This period of record for hydrology covers several of the extreme hydrologic events of the last century, including the historic dry period of record (1976 and 1977), a prolonged drought period (1987 through 1992), along with several historic wet or flood years (1983, 1986, and 1997). It is a sufficiently long period of record to be statistically valid for anticipating Project responses to a range of potential hydrologic conditions. This section describes some of the primary assumptions in the Base Case as they relate to hydrology. For a complete description of the YRDPM hydrology and the methodology used to compute it, see Attachment 2-2D, the Hydrology Report. 4.1 Sources of Inflows Project inflow, as simulated in the YRDPM, comes from several sources: historical data from U.S. Geological Survey (USGS) gages, and synthesized accretions. Figure shows the historical inflow locations and the areas for computed accretions Historical Inflows The YRDPM uses historical inflows from the gages shown in Table Table USGS gages used to determine historical inflows to the YRDPM. Tributary USGS Gage Number USGS Gage Name North Yuba River North Yuba River Below Goodyears Bar -- Slate Creek Slate Creek Below Diversion Dam, Near Strawberry Valley Notes -- Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

167 Table (continued) Oregon Creek Tributary Middle Yuba River USGS Gage Number USGS Gage Name Oregon Creek At Camptonville South Yuba River Oregon Creek Below Log Cabin Diversion Dam, Near Camptonville Camptonville Tunnel At Intake, Near Camptonville Middle Yuba River Below Milton Dam, Near Sierra City Lohman Ridge Tunnel At Intake, Near Camptonville Middle Yuba River Below Our House Diversion Dam, Near Camptonville South Yuba River At Jones Bar, Near Grass Valley Yuba County Water Agency Notes Scaled up by ratio of contributing watersheds to be representative of Oregon Creek at Log Cabin Diversion Dam. Added to Camptonville Tunnel flow less Lohman Ridge Tunnel flow to represent Oregon Creek flow above Log Cabin Diversion Dam. -- Scaled up by ratio of contributing watersheds to be representative of Middle Yuba River at Our House Diversion Dam. Added to Lohman Ridge Tunnel flow to represent Middle Yuba River flow above Log Cabin Diversion Dam. Deer Creek Deer Creek Near Smartville -- This data is generally used without modification, though missing data was filled in through interpolation, and some basic arithmetic changes were applied. The historical data includes historical upstream operations of the Yuba-Bear and Drum-Spaulding projects on the Middle and South Yuba rivers and Deer Creek, and the SFP on Slate Creek Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-15

168 Source: MWH Americas, Inc. Figure Historical and synthetic inflows to the YRDPM. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

169 4.1.2 Synthetic Inflows Accretions in the shaded regions shown in Figure were computed by scaling index watersheds by ratios of land area and average annual precipitation of the index watershed and the subbasin of interest. The two index watersheds used were the North Yuba River below Goodyears Bar, and Oregon Creek at Log Cabin Diversion Dam. These two were chosen because they represent unimpaired conditions and they are essentially unaffected by any humanmade impairments. As a result, they represent natural hydrologic conditions; the North Yuba River below Goodyears Bar is representative of high elevation watersheds largely driven by snow melt-related events, and Oregon Creek at Log Cabin Diversion Dam is representative of the middle elevation watersheds typically influenced by rainfall-related events. Table shows the areas and average annual precipitation for the index watersheds and the subbasins with synthesized accretions. Table Areas and average annual precipitation for YRDPM subbasins. Index Watersheds Subbasins with Synthesized Accretions Watershed Area (square miles) Average Annual Precipitation (inches) Index Watershed North Yuba River below Goodyears Bar Oregon Creek above Log Cabin Diversion Dam North Yuba River between Goodyears Bar and Slate Creek Canyon Creek Slate Creek Below Slate Creek Gage North Yuba River between Slate Creek and New Bullards Bar Dam North Yuba River below New Bullards Bar Oregon Creek above Log Cabin Diversion Dam Oregon Creek below Log Cabin Diversion Dam Middle Yuba River above Our House Diversion Dam Middle Yuba River between Our House Diversion Dam and Oregon Creek Middle Yuba River below Oregon Creek South Yuba River above Jones Bar Gage South Yuba River below Jones Bar Gage Yuba River above New Colgate Powerhouse Yuba River between New Colgate Powerhouse and Englebright Dam 1 Uses North Yuba River below Goodyears Bar as an index watershed. 2 Uses Oregon Creek above Log Cabin Diversion Dam as an index watershed. -- = Not Applicable Upstream Project Assumptions As previously mentioned, several of the tributaries to the Project are affected by ongoing FERC relicensings. This section describes the assumptions related to the inflows to the Project from those other projects. Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-17

170 4.2.1 Slate Creek The SFWPA has essentially completed its FERC relicensing process and is awaiting its new license. The Base Case uses historical releases from the Slate Creek Diversion Dam as inflows to the Project, and does not assume any changes in operations as a result of SFWPA s pending new FERC license Middle Yuba River NID recently submitted amendments to its Final License Application for the Yuba-Bear Project, but has not yet received a new FERC license. Accordingly, the Base Case uses historical flows in the Middle Yuba River at Our House Diversion Dam as inflows to the Project South Yuba River PG&E recently submitted amendments to its Final License Application for the Drum-Spaulding Project, but has not yet received a new FERC license. Accordingly, the Base Case uses historical flows in the South Yuba River near Jones Bar as inflows to the Project. 5.0 Other Project Operations Besides the regulatory requirements and agreements affecting Project operations, YCWA incorporates many other operational practices based on experience and practicality in Project operations. This section describes those operational practices as implemented in the YRDPM. 5.1 New Bullards Bar Reservoir Target Operating Line Operations During relatively wet periods when New Bullards Bar Reservoir is not being operated for flood management or minimum flow requirements, a target operating line is used to drive reservoir operations. Generally, when storage is above the target operating line, water is released from storage until the storage is at the target operating line. When storage is below the target operating line, releases are made for minimum flow requirements. However, operations for a strict target operating line result in very erratic and highly variable releases. To smooth releases, buffers are used on the target operating line. An upper and lower buffer are used to define a target operating zone for each date of the year, and intermediate dates are computed by interpolation between the defined dates. When daily reservoir storage is forecasted to be at the upper end of the target operating zone, releases are made from New Colgate Powerhouse at its maximum capacity, provided those flows would not exceed the powerhouse release capacity from Englebright Reservoir. If daily New Bullards Bar Reservoir storage is forecasted to be at the lower end of the target operating zone, releases are made from New Bullards Bar Reservoir for minimum flow requirements below Englebright Reservoir. If daily New Bullards Bar Reservoir storage is forecasted to be somewhere between the upper and lower buffers, New Bullards Bar Reservoir releases are computed by a linear interpolation between releases for minimum flow requirements and for maximum releases through New Colgate Powerhouse. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

171 Table shows the Base Case Target Operating Line and the buffers used to define the Target Operating Zone. Table Base Case New Bullards Bar Reservoir target operating line and buffers (TAF). Target Operating Line Upper Buffer 31- Oct 30- Nov 31- Dec 31- Jan 28- Feb 31- Mar 30- Apr Lower Buffer TAF = thousand acre-feet 31- May 30- Jun 15- Jul 31- Jul 15- Aug 31- Aug 30- Sep 5.2 New Bullards Bar Reservoir Carryover Storage Operations Carryover storage in New Bullards Bar Reservoir is used to ensure sufficient storage in the reservoir at the end of the water year to meet minimum flow requirements and to provide some water supply in case of a drought in the following year. For the Base Case, the carryover storage requirement is set so that there is sufficient water in storage on September 30 to meet Schedule 6 flow requirements and to provide 50 percent of the following year s agricultural demands for a 99 percent (%) exceedance drought. The carryover storage requirement also assumes the minimum New Bullards Bar Reservoir storage is 234,000 ac-ft, and that there would be 15 TAF of evaporation throughout the year. A 45 TAF buffer is also used to ensure sufficient water supply to meet requirements between October 1 and the end of November of the following water year, at which point California weather typically shifts to a wetter pattern. The result of these protections is a minimum carryover storage requirement of 294 TAF. The maximum carryover storage requirement is 440 TAF, representing the volume required to meet the Schedule 6 flow requirements, and 50 percent of agricultural demands, given a 99 percent exceedance hydrology, with a 10 TAF buffer, as opposed to the previously mentioned 45 TAF, which was used to ensure adequate storage to meet release requirements in October and November. The difference between the minimum and maximum carryover storage requirement is due to a desire to protect against both a one-year and a two-year drought. In a 99% exceedance two-year drought, the average annual runoff volume is much higher than a 99% exceedance single-year drought. Accordingly, the carryover storage requirement for a second year of a drought, where there would statistically be more runoff than the 99% exceedance first year of a drought, is lower than that for the first year of a drought. 5.3 New Colgate Powerhouse Operations New Colgate Powerhouse is generally used to provide water supply to Englebright Reservoir and subsequently the lower Yuba River. However, once the volume of water required for release from New Bullards Bar Reservoir to meet those downstream needs has been determined, the YRDPM includes logic for reoperation of New Colgate Powerhouse to release that volume on an economically beneficial schedule. This operation is not included in the Base Case scenario. Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-19

172 New Colgate Powerhouse releases are determined based on either downstream needs or for New Bullards Bar Reservoir storage management. 5.4 Englebright Reservoir Operations Releases from Englebright Reservoir are generally made to meet lower Yuba River flow requirements and irrigation demand, or in response to storage operations from New Bullards Bar Reservoir. This section describes some of the specific operational assumptions included in the Base Case Reservoir Levels In modeling, Englebright Reservoir levels rarely fluctuate. The initial storage and target storage of Englebright Reservoir are both set at 30,947 ac-ft, corresponding to an elevation of 519 ft-msl, for the Base Case. With the exception of a few specific operations, the YRDPM maintains Englebright Reservoir at its target storage. As previously discussed, New Bullards Bar Reservoir makes releases to ensure lower Yuba River requirements are met, and in the situation that New Bullards Bar Reservoir is operating for storage considerations, Englebright Reservoir releases all inflows up to the release capacity of the two Narrows Powerhouses. This ensures Englebright Reservoir storage does not change under normal operations. Englebright Reservoir s levels are fluctuated in anticipation of, and in response to, storm events; when inflows are expected to exceed the combined capacity of the two Narrows Powerhouses, the YRDPM reduces New Colgate Powerhouse releases, but does not reduce Englebright Reservoir releases. This action results in a reduction of Englebright Reservoir storage and allows Englebright Reservoir to capture some portion of the storm without spilling. The minimum elevation for Englebright Reservoir is set at 516 ft-msl for the Base Case in recognition of an operational agreement PG&E has with the Skippers Cove Marina. As part of this operation, Englebright Reservoir s storage increases as it captures the storm event. When the Englebright Reservoir water surface elevation reaches 523 ft-msl, releases are set at the combined maximum capacity of the two Narrows powerhouses. When the water surface elevation reaches 527 ft-msl, Englebright Reservoir begins to spill. Once the storm event has passed, and Englebright Reservoir has stopped spilling, releases are maintained at the maximum combined Narrows Powerhouses capacity until storage returns to the target storage, at which point, operations for either instream flow requirements or New Bullards Bar Reservoir storage are resumed Fluctuation for Power Generation In response to re-operation of New Colgate Powerhouse as described in Section 5.3, Englebright Reservoir storage would fluctuate to ensure consistent releases to the lower Yuba River in spite of fluctuations in New Colgate Powerhouse releases. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

173 5.4.3 Division of Flow between Narrows 1 and 2 Powerhouses Yuba County Water Agency After the YRDPM determines total releases from Englebright Reservoir, a separate module allocates releases to the various release mechanisms. While the division of flow between Narrows 1 and 2 Powerhouses does not affect flow in the lower Yuba River, it could have an effect on water temperatures and generation. The Base Case includes a preference for using the Narrows 1 Powerhouse. Recent Renewable Portfolio Standards provide economic benefits to PG&E to use Narrows 1 Powerhouse over Narrows 2 Powerhouse, when possible, and these incentives are reflected in current project operations. Table shows the division of releases from Englebright Reservoir according to flow range. Table Division of Englebright Reservoir releases by flow rate (cfs). Flow Range Narrows 1 Release Narrows 2 Release Bypass Spill , ,630-4, , >4, ,400 0 All remaining flow Note: Bypass indicates releases through the Narrows 2 Bypass, with no generation. cfs = cubic feet per second 5.5 Groundwater Substitution Transfers The Yuba Accord requires that YCWA provide 30 TAF of groundwater substitution transfer in Schedule 6 years. This transfer would involve YCWA member units pumping 30 TAF of groundwater, and allowing the water they would otherwise have diverted to be released from New Bullards Bar Reservoir at a time when the water would be usable by downstream interests. Table shows the assumed pumping and release patterns, as included in the Base Case scenario. Table Groundwater substitution transfer monthly pumping and release patterns. Apr May Jun Jul Aug Sep Oct Nov Dec Total Groundwater Pumping Pattern 0% 5% 15% 30% 30% 5% 10% 5% 0% 100% Transfer Release Pattern 0% 0% 10% 50% 40% 0% 0% 0% 0% 100% Note: Based on historical transfers for Summary of Base Case Scenario Modeling Assumptions Table summarizes the modeling assumptions from the Base Case scenario. Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-21

174 Table Base Case scenario modeling assumptions Location Basics Middle Yuba River Oregon Creek New Bullards Bar Reservoir Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Agricultural Delivery Level of Development: Present (291 TAF in Wet Years, 305 TAF in Dry Years) Starting Agricultural Delivery Deficiency: 0% Inflow: Historical above Our House Diversion Dam Accretions: Synthetic Minimum Flow below Our House Diversion Dam (cfs): Per FERC 2246 License June 16-April 14: 30 April 15-June 15: 50 Minimum Flow Buffer (cfs): 3 Lohman Ridge Tunnel Capacity (cfs): 860 Ramping Rate (cfs): None Inflow: Historical above Log Cabin Diversion Dam Accretions: Synthetic Minimum Flow below Log Cabin Diversion Dam (cfs): Per FERC 2246 License June 16-April 14: 8 April 15-June 15: 12 Minimum Flow Buffer (cfs): 1 Camptonville Tunnel Capacity (cfs): 1,100 Ramping Rate (cfs): None Inflow: Historical at Goodyears Bar Historical below Slate Creek Diversion Dam Accretions: Synthetic New Bullards Bar Reservoir Gross Pool Elevation (ft-msl): 1,956 New Bullards Bar Reservoir Gross Pool Storage (ac-ft): 966,103 New Bullards Bar Reservoir Minimum Pool Storage (ac-ft): Per FERC 2246 License 234,000 New Bullards Bar Reservoir Flood Reservation (TAF): Per 1972 USACE Flood Control Manual October 31-March 31: 170 April 30: 100 May 31-September 15: 0 Flood Reservation Space Buffer (ac-ft): 8,000 Minimum Flow below New Bullards Bar Dam (cfs): Per FERC 2246 License Year-Around: 5 (from Fish Hydro) Minimum Flow Buffer (cfs): 2 Maximum Flow below New Bullards Bar Dam (cfs): Per 1972 USACE Flood Control Manual 50,000 Ramping Rate: None Spillway Elevation-Release Capacity: Maximum Per 1972 USACE Flood Control Manual New Bullards Bar Reservoir Target Storage (ac-ft): September 30: 650,000 October 31: 660,000 Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

175 Table (Continued) Location Basics New Bullards Bar Reservoir Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Yuba County Water Agency Agricultural Delivery Level of Development: Present (291 TAF in Wet Years, 305 TAF in Dry Years) Starting Agricultural Delivery Deficiency: 0% November 30: 660,000 December 31: 650,000 September 30: 650,000 October 31: 660,000 November 30: 660,000 December 31: 650,000 January 31: 600,000 February 28: 650,000 March 31: 750,000 April 30: 850,000 May 31: 940,000 June 30: 920,000 July 15: 875,000 July 31: 825,000 August 15: 770,000 August 31: 715,000 Linearly interpolated for intermediate dates New Bullards Bar Reservoir Target Storage Buffers (Upper/Lower) (ac-ft): September 30: 20,000 /10,000 October 31: 20,000 /10,000 November 30: 30,000 /30,000 December 31: 30,000 /30,000 January 31: 80,000 /30,000 February 28: 30,000 /30,000 March 31: 30,000 /30,000 April 30: 30,000 /30,000 May 31: 26,000 /100,000 June 30: 0 / 80,000 July 15: 5,000 /60,000 July 31: 10,000 /40,000 August 15: 10,000 /35,000 August 31: 10,000 /15,000 Linearly interpolated for intermediate dates Reservoir Evaporation (inches): October: 4.31 November: 1.67 December: 1.04 January: 0.93 February: 1.70 March: 2.44 April: 3.21 May: 4.13 June: 6.48 July: 7.78 August: 7.24 September: 5.08 Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-23

176 Table (Continued) Basics Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Agricultural Delivery Level of Development: Starting Agricultural Delivery Deficiency: 0% Present (291 TAF in Wet Years, 305 TAF in Dry Years) Location New Bullards Bar Reservoir New Colgate Powerhouse Englebright Reservoir Carryover Storage Buffer (TAF): 45 Annual Evaporation for Carryover Storage Calculation (TAF): New Colgate Powerhouse Release Capacity (cfs): 3,430 New Colgate Powerhouse Minimum Release (cfs): 0 New Colgate Powerhouse Turbine Elevation (ftmsl): 565 Maximum New Colgate Powerhouse Reduction 30% (preserve 70% of original releases) for Englebright Reservoir Spill Avoidance: New Colgate Powerhouse Flow Head Generation: Based on empirical data ( ) New Colgate Powerhouse Generation Factors Applied: None Ramping Rate: Inflow: Accretions: 15 None Historical South Yuba River at Jones Bar Synthetic Englebright Dam Crest Elevation (ft-msl): 527 Englebright Reservoir Minimum Operating Elevation (ft-msl): 516 Englebright Reservoir Target Operating Elevation (ft-msl): 519 Englebright Reservoir Target Operating Storage (ac-ft): 30,947 Englebright Reservoir Stage Storage Curve: As provided by YCWA 5/10/2012 Englebright Reservoir Stage Spill Relationship: As provided by YCWA 5/10/2012 Narrows 1 Powerhouse Maximum Release Capacity (cfs): 720 New Bullards Bar Reservoir Target Storage Buffers (Upper/Lower) (ac-ft): Narrows 1 Powerhouse Minimum Release (cfs): 71 Narrows 2 Powerhouse Maximum Release Capacity (cfs): 3,400 Narrows 2 Powerhouse Minimum Release (cfs): 900 Narrows 1 Powerhouse Flow Head-Generation Relationship: Developed based on PG&E flow test Narrows 2 Powerhouse Flow Head-Generation Relationship: Based on empirical data ( ) Narrows 1 and 2 Powerhouses' Tailwater Elevation (ft-msl): 287 Elevation trigger for Maximum Narrows Release (ft-msl): 523 Narrows 1 and 2 Powerhouses Flow Split: Favor use of Narrows 1 powerhouse for "Green Energy Credits" Englebright Reservoir Water Surface Area (acres): 810 Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

177 Table (Continued) Location Basics Englebright Reservoir Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Agricultural Delivery Level of Development: Yuba County Water Agency Present (291 TAF in Wet Years, 305 TAF in Dry Years) Starting Agricultural Delivery Deficiency: 0% Inflow: Historical South Yuba River at Jones Bar Accretions: Synthetic Englebright Dam Crest Elevation (ft-msl): 527 Englebright Reservoir Minimum Operating Elevation (ft-msl): 516 Englebright Reservoir Target Operating Elevation (ft-msl): 519 Englebright Reservoir Target Operating Storage (ac-ft): 30,947 Englebright Reservoir Stage Storage Curve: As provided by YCWA 5/10/2012 Englebright Reservoir Stage Spill Relationship: As provided by YCWA 5/10/2012 Narrows 1 Powerhouse Maximum Release Capacity (cfs): 720 New Bullards Bar Reservoir Target Storage Buffers (Upper/Lower) (ac-ft): Narrows 1 Powerhouse Minimum Release (cfs): 71 Narrows 2 Powerhouse Maximum Release Capacity (cfs): 3,400 Narrows 2 Powerhouse Minimum Release (cfs): 900 Narrows 1 Powerhouse Flow Head-Generation Relationship: Developed based on PG&E flow test Narrows 2 Powerhouse Flow Head-Generation Relationship: Based on empirical data ( ) Narrows 1 and 2 Powerhouses' Tailwater Elevation (ft-msl): 287 Elevation trigger for Maximum Narrows Release (ft-msl): 523 Narrows 1 and 2 Powerhouses Flow Split: Favor use of Narrows 1 powerhouse for "Green Energy Credits" Englebright Reservoir Water Surface Area (acres): 810 Reservoir Evaporation (inches): October: 5.03 November: 1.95 December: 1.21 January: 1.09 February: 1.99 March: 2.85 April: 3.75 May: 4.83 June: 7.58 July: 9.09 August: 8.46 September: 5.95 Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-25

178 Table (continued) Location Basics Englebright Reservoir Lower Yuba River Scenario Name: Base Case Period of Simulation: 10/1/1969-9/30/2010 New Bullards Bar Reservoir Starting Storage (ac-ft): 551,051 Englebright Reservoir Starting Storage (ac-ft): 30,947 Agricultural Delivery Level of Development: Present (291 TAF in Wet Years, 305 TAF in Dry Years) Starting Agricultural Delivery Deficiency: 0% April: 3.75 May: 4.83 June: 7.58 July: 9.09 August: 8.46 September: 5.95 Number of Days Forward to Look for Forecasting Freshets (days): 4 Inflow: Accretions: Minimum Flow at Smartville Gage: Smartville Gage Buffer: Minimum Flow at Marysville Gage: Marysville Gage Buffer: Maximum Flow at Marysville gage: Daguerre Point Diversion Demand: Groundwater Substitution Transfers: Flow Stability Criteria: Maximum Flow Above Minimum Flows for September 1- October 31 (cfs): Ramping Rate (cfs): Englebright Spill Avoidance: Historical Deer Creek near Smartville Synthetic Dry Creek near confluence None Per Yuba River Accord None, Accord flow schedules applied on a 5-day average Per Yuba River Accord None, Accord flow schedules applied on a 5-day average Per 1972 USACE Flood Control Manual 120,000 cfs Based on 2005 land use and published applied water rates Daily patterns based on historical deliveries Present Level Demands (291,197 ac-ft wet/ 305,081 ac-ft Dry) Per Yuba Accord, 30 TAF in Schedule 6 years Per FERC 2246 License Amendment Only applies to controlled events Maximum reduction to 70% of previous day's flow Maximum reduction to 55% of September 15-October 31 flow Maximum reduction to 65% of November 1-March 31 flow 300 Maximum daily reduction of 200 cfs If forecasted inflow to Englebright Reservoir (assumes 4 days of perfect foresight) exceeds Narrows 1 and 2 combined release capacity, reduce New Colgate generation to create space in Englebright Reservoir as long as it does not result in New Bullards Bar Reservoir encroaching on its flood reservation. Other Assumptions New Bullards Bar Reservoir Target Operating Line Operations: Instream flow Requirements: Low New Bullards Bar Reservoir Storage: If forecasted storage, with operations for instream flows, would result in New Bullards Bar Reservoir storage in excess of upper target operating line buffer (but below flood pool), run New Colgate Powerhouse at maximum capacity, providing it does not spill Englebright Reservoir. If forecasted storage would be below lower target operating line buffer (but above minimum pool), make releases for lower Yuba River flow requirements. Forecasted storage within buffer zone results in releases that are linearly interpolated between the two extremes. Computed assuming perfect foresight for the year. Are in effect for April 1 through March 31 If New Bullards Bar Reservoir storage reaches the FERC minimum pool, inflows are released up to the instream flow requirement. ac-ft = acre-feet cfs = cubic feet per second TAF = thousand acre-feet ft-msl =feet above mean sea level Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

179 Some operational practices, such as Browns Valley Irrigation District s (BVID) 3,100 af annual conserved water transfer, and YCWA member unit discretionary groundwater substitution transfers are not included in the Base Case scenario. While YCWA helps facilitate these practices, they are not YCWA operations. Similarly, some regulatory practices, such as the 2012 National Oceanic and Atmospheric Association (NOAA) National Marine Fisheries Service (NMFS) Biological Opinion (BO) on the USACE s continued operation and maintenance (O&M) of Englebright and Daguerre Point dams, are not explicitly included in the Base Case scenario since they do not affect the way Project operations would be modeled. 7.0 Base Case Scenario Output The Base Case scenario yields daily output usable by other resource areas. This section provides a summary of some key output constituents. 7.1 Our House Diversion Dam Releases Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean daily flow on the Middle Yuba River below Our House Diversion Dam for the Base Case scenario for the period of record. Table Simulated monthly average Middle Yuba River flow below Our House Diversion Dam (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-27

180 Figure Exceedance probability of simulated mean daily middle Yuba River Flow below Our House Diversion Dam for the Base Case scenario (WY ). 7.2 Lohman Ridge Tunnel Flow Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean daily flow in the Lohman Ridge Tunnel for the Base Case scenario for the period of record. Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

181 Table Simulated monthly average flow in the Lohman Ridge Tunnel (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Figure Exceedance probability of simulated mean daily flow in the Lohman Ridge Tunnel for the Base Case scenario (WY ). 7.3 Log Cabin Diversion Dam Releases Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean daily flow in Oregon Creek below Log Cabin Diversion Dam for the Base Case scenario for the period of record. Table Simulated monthly average Oregon Creek flow below Log Cabin Diversion Dam (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-29

182 Figure Exceedance probability of simulated mean daily flow in Oregon Creek below Log Cabin Diversion Dam for the Base Case scenario (WY ). 7.4 Camptonville Tunnel Flow Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean daily flow in the Camptonville Tunnel for the Base Case scenario for the period of record. Table Simulated monthly average Camptonville Tunnel flow. (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

183 Figure Exceedance probability of simulated mean daily Camptonville Tunnel flow for the Base Case scenario (WY ). 7.5 New Bullards Bar Reservoir Storage Table shows the simulated monthly average storage, and Figure shows the exceedance probability of the simulated mean daily storage in New Bullards Bar Reservoir for the Base Case scenario for the period of record. Table Simulated monthly average New Bullards Bar Reservoir storage. (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (ac-ft) 619, , , , , , , , , , , ,650 ac-ft = acre-feet Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-31

184 Figure Exceedance probability of simulated mean daily New Bullards Bar Reservoir storage for the Base Case scenario (WY ). 7.6 New Bullards Bar Reservoir Spill Table shows the simulated monthly average spill and Figure shows the exceedance probability of the simulated mean daily spill from New Bullards Bar Reservoir for the Base Case scenario for the period of record. Table Simulated monthly average New Bullards Bar Reservoir spill (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Figure Exceedance probability of simulated mean daily New Bullards Bar Reservoir spill for the Base Case scenario (WY ). Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

185 7.7 New Bullards Bar Minimum Flow Hydro Releases Yuba County Water Agency Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean daily flow from the New Bullards Bar Minimum Flow Hydro for the Base Case scenario for the period of record. Table Simulated Monthly Average New Bullards Bar Reservoir Release through the New Bullards Bar Minimum Flow Hydro. (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Figure Exceedance probability of simulated mean daily new Bullards Bar Reservoir release through the Fish Hydro for the Base Case scenario (WY ). 7.8 New Colgate Powerhouse Releases Table shows the simulated monthly average release and Figure shows the exceedance probability of the simulated mean daily release from the New Colgate Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average New Colgate Powerhouse release (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) 1,443 1,791 1,782 1,533 2,328 2,251 1,933 1, cfs = cubic feet per second Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-33

186 Figure Exceedance probability of simulated mean daily New Colgate Powerhouse release for the Base Case scenario (WY ). 7.9 New Colgate Powerhouse Generation Table shows the simulated monthly average generation and Figure shows the exceedance probability of the simulated mean daily generation at the New Colgate Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average New Colgate Powerhouse generation (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (MWh) 3,219 3,996 4,015 3,586 5,560 5,348 4,546 3,500 1,899 1,623 1,693 2,101 MWh = megawatt hours Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

187 Figure Exceedance probability of simulated mean daily New Colgate Powerhouse generation for the Base Case scenario (WY ) Englebright Reservoir Elevation Table shows the simulated monthly average water surface elevation and Figure shows the exceedance probability of the simulated mean daily water surface elevation of Englebright Reservoir for the Base Case scenario for the period of record. Table Simulated monthly average Englebright Reservoir water surface elevation (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (feet) Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-35

188 Figure Exceedance probability of simulated mean daily Englebright Reservoir water surface elevation for the Base Case scenario (WY ) Narrows 1 Powerhouse Releases Table shows the simulated monthly average release and Figure shows the exceedance probability of the simulated mean daily release from PG&E s Narrows 1 Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average Narrows 1 Powerhouse releases (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

189 Figure Exceedance probability of simulated mean daily releases from PG&E s Narrows 1 Powerhouse for the Base Case scenario (WY ) Narrows 1 Powerhouse Generation Table shows the simulated monthly average generation and Figure shows the exceedance probability of the simulated mean daily generation at PG&E s Narrows 1 Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average Narrows 1 Powerhouse generation (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (MWh) MWh = megawatt hours Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-37

190 Figure Exceedance probability of simulated mean daily Narrows 1 Powerhouse generation for the Base Case scenario (WY ) Narrows 2 Powerhouse Releases Table shows the simulated monthly average release and Figure shows the exceedance probability of the simulated mean daily release from the Narrows 2 Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average Narrows 2 Powerhouse releases (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) 1,521 1,925 2,024 1,737 2,345 2,028 1,457 1, cfs = cubic feet per second Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

191 Figure Exceedance probability of simulated mean daily releases from the Narrows 2 Powerhouse for the Base Case scenario (WY ) Narrows 2 Powerhouse Generation Table shows the simulated monthly average generation and Figure shows the exceedance probability of the simulated mean daily generation at the Narrows 2 Powerhouse for the Base Case scenario for the period of record. Table Simulated monthly average Narrows 2 Powerhouse generation (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (MWh) MWh = megawatt hours Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-39

192 Figure Exceedance probability of simulated mean daily Narrows 2 Powerhouse generation for the Base Case scenario (WY ) Narrows 2 Bypass Table shows the simulated monthly average release and Figure shows the exceedance probability of the simulated mean daily release from the Narrows 2 Bypass for the Base Case scenario for the period of record. Table Simulated monthly average Narrows 2 bypass releases (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

193 Figure Exceedance probability of simulated mean daily releases from the Narrows 2 Bypass for the Base Case scenario (WY ) Englebright Reservoir Spill Table shows the simulated monthly average spill and Figure shows the exceedance probability of the simulated mean daily Englebright Reservoir spill for the Base Case scenario for the period of record. Table Simulated monthly average Englebright Reservoir spill (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) 1,443 1,129 1, cfs = cubic feet per second Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-41

194 Figure Exceedance probability of simulated mean daily releases from the Narrows 2 Bypass for the Base Case scenario (WY ) Smartville Flow Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean Yuba River flow at Smartville for the Base Case scenario for the period of record. Table Simulated monthly average Yuba River flow at Smartville (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) 3,619 3,720 3,894 2,933 3,957 3,235 2,133 1, ,163 2,093 cfs = cubic feet per second Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

195 Figure Exceedance probability of simulated mean daily Yuba River flow at Smartville for the Base Case scenario (WY ) Agricultural Deliveries Table shows the simulated monthly average and Figure shows the exceedance probability of the simulated mean daily combined agricultural delivery from Daguerre Point Dam for the Base Case scenario for the period of record. Table Simulated monthly average combined agricultural delivery from Daguerre Point Dam (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) cfs = cubic feet per second Base Case Scenario Report Technical Memorandum 2-2 Attachment 2-2C November , Yuba County Water Agency Page C-43

196 Figure Exceedance probability of simulated mean daily combined agricultural deliveries from Daguerre Point Dam for the Base Case scenario (WY ) Marysville Flow Table shows the simulated monthly average flow and Figure shows the exceedance probability of the simulated mean Yuba River flow at Marysville for the Base Case scenario for the period of record. Table Simulated monthly average Yuba River flow at Marysville (WY ). Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Monthly Average (cfs) 3,981 4,262 4,490 3,043 3,360 2,410 1, ,047 cfs = cubic feet per second Figure Exceedance probability of simulated mean daily Yuba River flow at Marysville for the Base Case scenario (WY ). Attachment 2-2C Technical Memorandum 2-2 Base Case Scenario Report Page C , Yuba County Water Agency November 2012

197 Technical Memorandum 2-2 Water Balance/Operations Model Attachment 2-2D Hydrology Report November , Yuba County Water Agency All Rights Reserved

198

199 Table of Contents Section No. Description Page No. 1.0 Introduction... D The Yuba River Watershed... D Summary of Hydrologic Analysis... D Water Year Types... D Yuba River Index... D North Yuba Index... D Major Tributary flows... D North Yuba River... D Slate Creek... D Middle Yuba River... D South Yuba River... D Oregon Creek... D Deer Creek... D Ungaged Accretions... D Accretions to New Bullards Bar Reservoir... D Calculation of Accretions to New Bullards Bar Reservoir Using Mass Balance Methodology... D Estimation of Accretions to New Bullards Bar Reservoir Using Statistical Regression Methodology... D Estimation of Accretions to New Bullards Bar Reservoir using Area-Weighted Flow Methodology... D Comparison of Accretions Calculation and Estimations... D Computation of Ungaged Accretions to North Yuba River above New Bullards Bar Dam Subbasins... D Computation of New Bullards Bar Reservoir Evaporation... D Accretions to Englebright Reservoir... D Comparison of Englebright Accretions Calculation and Estimation... D Computation of Ungaged Accretions from Subbasins to the Yuba River above Englebright Dam... D Computation of Englebright Reservoir Evaporation... D Lower Yuba River Accretions... D Dry Creek... D Unimpaired Flows... D North Yuba River... D Middle Yuba River... D-45 Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page TOC-i

200 Table of Contents (continued) Section No. Description Page No. 4.3 South Yuba River... D Unimpaired Yuba River flow at Smartsville... D Accumulated Flows... D North Yuba River at New Bullards Bar Dam... D Middle Yuba River at its Confluence with the North Yuba River... D South Yuba River at its Confluence with the Yuba River... D Yuba River at Smartsville... D References... D-57 List of Figures Figure No. Description Page No Yuba River Watershed... D YRDP Project Area Tributary Reaches... D Schematic of Lower Yuba River USGS Gage Network... D Gage Network of the North Yuba River... D Gage Network of Slate Creek flows to New Bullards Bar... D Gage Network of Middle Yuba River around Our House Dam... D Gage Network of the Lower South Yuba River... D Gage Network of Oregon Creek above Log Cabin Dam... D Gage Network of Deer Creek Flow near Smartsville.... D Yuba River Watershed and Subbasins... D Yuba River Watershed and Subbasin Average Annual Precipitation... D Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to New Bullards Bar Reservoir... D Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to New Bullards Bar Reservoir with Colgate Powerhouse Gage Correction... D Yuba River Ungaged Accretion Subbasins... D Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to Englebright Reservoir... D Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to Englebright Reservoir with Gage Correction Factors... D Middle Yuba River Subbasin between Milton Diversion Dam and Our House Dam... D-46 Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page TOC-ii 2012, Yuba County Water Agency November 2012

201 List of Figures Figure No. Description Page No South Yuba River Subbasin between Canyon Creek, Langs Crossing, and Jones Bar... D Comparison of Accumulated Unimpaired Flow at Smartsville (WY ).... D-50 List of Tables Table No. Description Page No Historical Yuba River Index Year-Types 1970 to D North Yuba Index Values and Schedules from 2008 through D USGS Gages Used to Determine Major Tributary Flows... D Historical Average Monthly North Yuba River Flow at Goodyears Bar.... D Historical Average Monthly Slate Creek Flows below the Slate Creek Tunnel.... D Historical Average Monthly Middle Yuba River Flows above Our House Dam.... D Historical Average Monthly South Yuba River Flows at Jones Bar.... D Corrections to Computed Historical Oregon Creek Flows above Log Cabin Dam.... D Historical Average Monthly Oregon Creek Flows above Log Cabin Dam.... D Historical Average Monthly Deer Creek Flows near Smartsville.... D New Bullards Bar Reservoir Tributaries... D Applied Colgate Powerhouse Gage Correction Factors... D Ungaged North Yuba River above New Bullards Bar Dam Subbasins.... D Computed Monthly Average Accretions to the North Yuba River between Goodyears Bar and Slate Creek.... D Computed Monthly Average Accretions to Canyon Creek.... D Computed Monthly Average Accretions to Slate Creek between the Slate Creek Diversion Dam and Slate Creek s Confluence with the North Yuba River.... D Computed Monthly Average Accretions New Bullards Bar Reservoir.... D Computed Monthly Evaporation Rates for New Bullards Bar Reservoir.... D Computed Historical Monthly Average New Bullards Bar Reservoir Evaporation.... D Sources of Inflows to Englebright Reservoir.... D Applied Smartsville Gage Correction Factors... D Computed Monthly Average Accretions to the Middle Yuba River between Our House Dam and Oregon Creek.... D-39 Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page TOC-iii

202 List of Tables (continued) Table No. Description Page No Computed Monthly Average Accretions to the Middle Yuba River below Oregon Creek.... D Computed Monthly Average Accretions to the Oregon Creek below Log Cabin Dam.... D Computed Monthly Average Accretions to the South Yuba River below Jones Bar.... D Computed Monthly Average Accretions Englebright Reservoir.... D Computed Monthly Englebright Reservoir Evaporation Rates.... D Computed Monthly Englebright Reservoir Evaporation Volumes.... D Monthly Coefficients for Computing Dry Creek Flow from Deer Creek Gage Data.... D Monthly Average Computed Dry Creek Accretions to the Yuba River.... D Computed Monthly Average Unimpaired North Yuba River Flow at New Bullards Bar Dam.... D Monthly Average Unimpaired Middle Yuba River Flow at its Confluence with the North Yuba River.... D Monthly Average Unimpaired South Yuba River Flow at its Confluence with the Yuba River.... D Computed Monthly Average Unimpaired Yuba River Flow at Smartsville.... D Historical Monthly Average North Yuba River Flow at New Bullards Bar Dam.... D Computed Monthly Average North Yuba River Flow at New Bullards Bar Dam in the Absence of the YRDP.... D Comparison of Monthly Average North Yuba River Flow at New Bullards Bar Dam Site under Various Developmental Conditions.... D Historical Monthly Average Middle Yuba River Flow at its Confluence with the North Yuba River.... D Computed Monthly Average Flow on the Middle Yuba River at its Confluence with the North Yuba River in the Absence of the YRDP.... D Comparison of Monthly Average Middle Yuba River Flow at its Confluence with the North Yuba River under Various Developmental Conditions.... D Historical Monthly Average South Yuba River Flow at its Confluence with the Yuba River.... D Comparison of Monthly Average South Yuba River Flow at its Confluence with the Yuba River under Various Developmental Conditions.... D Historical Monthly Average Yuba River Flow at Smartsville.... D-56 Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page TOC-iv 2012, Yuba County Water Agency November 2012

203 List of Tables (continued) Table No. Description Page No Monthly Average Yuba River Flow at Smartsville without the YRDP.... D Comparison of Monthly Average Yuba River Flow at Smartsville under Various Developmental Conditions.... D-57 Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page TOC-v

204 Page Left Blank Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page TOC-vi 2012, Yuba County Water Agency November 2012

205 1.0 Introduction The purpose of this document is to describe the relevant hydrology of the Yuba River Watershed that affects, or is affected by, the (YRDP), Federal Energy Regulatory Commission (FERC) Project No. 2246, and to describe the methodologies for compiling relevant hydrologic information into a data set that will be used by the Licensee for studies and will be available to relicensing participants and stakeholders. 1.1 The Yuba River Watershed The Yuba River watershed drains approximately 1,339 square miles (USGS 2004) of the western slope of the Sierra Nevada, including portions of Sierra, Placer, Yuba, and Nevada counties, as shown in Figure The Yuba River is a tributary of the Feather River, which in turn is a tributary of the Sacramento River. The watershed rises from an elevation of about 60 feet to about 8,590 feet above mean sea level (msl). The annual unimpaired flow at the Smartsville Gage on the lower Yuba River has ranged from a high of 4.93 million acre-feet (MAF) in 1982 to a low of 0.37 MAF in 1977, with an average of about 2.37 MAF per year (1901 to 2008). 1 In general, runoff is almost equally divided between runoff from rainfall during October through March and runoff from snowmelt during April through September. 1 The forecasted seasonal unimpaired flow at Smartsville is estimated each year by the California Department of Water Resources and reported monthly in Bulletin 120, Water Conditions in California. The unimpaired flow at Smartsville is used in Yuba County Water Agency contracts for water delivery to senior water right holders on the lower Yuba River, and is used in the calculation of the Yuba River Index, a hydrologic water year type index for the Yuba River, defined in State Water Resources Control Board Revised Decision Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-1

206 Source: MWH Americas, Inc. Figure Yuba River Watershed Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

207 The upper basins of the Middle Yuba and South Yuba rivers have been extensively developed for hydroelectric power generation and consumptive uses by Nevada Irrigation District (NID) and Pacific Gas and Electric Company (PG&E). Total storage capacity of about 307 thousand acre-feet (TAF) on the Middle Yuba and South Yuba rivers and associated diversion facilities enable both NID and PG&E to export an average of approximately 410 TAF per year from the Yuba River watershed to the Bear River and American River basins through the Yuba-Bear (YB) and Drum-Spaulding (DS) projects, known collectively as the YB-DS projects. In addition, the South Feather Water and Power Agency (SFWPA, previously known as the Oroville-Wyandotte Irrigation District) exports an average of about 70 TAF per year from Slate Creek (a tributary to the North Yuba River) to the Feather River Watershed through the South Fork Feather River Project (SFFRP). While these upper basins lie outside of the project study area, the described operations and exports can considerably reduce the water supply available to the lower Yuba River, particularly during dry and critical water years. The U.S. Army Corps of Engineers (USACE) and the Yuba County Water Agency (YCWA) own storage facilities in the lower reaches of the Yuba River watershed. Two of the lower Yuba River facilities, Englebright Dam and Daguerre Point Dam, were originally constructed by the California Debris Commission, a Federal and State partnership, for debris control, and now are operated and maintained by the USACE. The YRDP, constructed and operated by YCWA, is a multiple-use project that provides flood control, power generation, irrigation, recreation, and protection and enhancement of fish and wildlife. It includes Our House and Log Cabin diversion dams, New Bullards Bar Dam and Reservoir, New Colgate Powerhouse, and Narrows 2 Powerhouse. Englebright Dam and Reservoir and Daguerre Point Dam are not part of the YRDP. Englebright Dam is used by YCWA and PG&E to regulate releases from New Colgate Powerhouse to the lower Yuba River, and Daguerre Point Dam is used by YCWA to divert water to its member units. 1.2 Summary of Hydrologic Analysis Section 1.3 presents a review of the two Water Year type indices for the lower Yuba River that have been developed over the past ten years. These indices are the Yuba River Index (YRI), developed for the State Water Resources Control Board (SWRCB) water rights hearings in 2000, and the North Yuba Index (NYI), developed for the Yuba Accord (YCWA 2007). YCWA has compiled two hydrology datasets used for the evaluations in this study: 1) historical hydrology and without-project hydrology. The description of each is included below: Historical Hydrology (i.e., gaged flows). The Historical Hydrology is the measured (i.e., gaged) hydrology in the basin. This data set is composed of the measured hydrology from Water Year (WY) 1970 through WY 2010 for the geographic area from just upstream of the Project to the United States Geological Survey (USGS) Marysville streamflow gage, which is located on the Yuba River upstream of the Feather River. The Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-3

208 Historical Hydrology data set for locations below Project facilities is representative of Project operations throughout its history. 2 Without-Project Hydrology. The Without-Project Hydrology indicates the hydrology as if the Project had not been constructed (i.e., no Project facilities in place) but all other water projects in the basin are operating. This data set is comprised of measured hydrology and synthesized hydrology from WY 1970 through WY 2010 for the geographic area from just upstream of the Project to the Marysville gage. The without- Project hydrology for areas upstream from the Project is the measured hydrology from the Historical Hydrology data set (i.e., inflow to the Project). The without-project Hydrology downstream of Project facilities is synthesized hydrology that consists of calculated accretions downstream from the inflow measurement locations plus the relevant measured inflow (i.e. in the Project area and downstream). Inflows to the Project Area 3 are a combination of both gaged tributary inflows and ungaged accretions. Gaged tributary flows are discussed in Section 2 for the following major tributaries: North Yuba River Slate Creek Middle Yuba River South Yuba River Oregon Creek Deer Creek Ungaged accretions and the methodologies used to compute them are discussed in Section 3. Subbasin ungaged accretions are discussed as either inflows to New Bullards Bar Reservoir (NBB), Englebright Reservoir, or the lower Yuba River and the components of flow that make up these three subbasin accretions. Yuba River flows are affected by the upstream projects including NID s Yuba-Bear Project, PG&E s Drum-Spaulding Project, and SFWPA s South Fork Feather River Project in addition to the YRDP. Section 4 includes a discussion of the calculation of unimpaired flows throughout the basin, including from the upstream projects. Section 5 includes a discussion of hydrologic analysis at four locations for three hydrologic conditions: a natural, unimpaired condition reflecting hydrology in the watershed without any human impairments, a Without-Project condition reflecting hydrology in the watershed without the YRDP, and a Historical condition 2 3 A significant shift in the Historical Hydrology occurred in From WY 1970 through WY 2005 the Project was operated under either the FERC license minimum flow requirements or the California State Water Resource Control Board (SWRCB) Revised Decision 1644 (RD-1644). Beginning in WY 2006, the Project was operated under the Yuba River Accord flow requirements, which are higher than the flow requirements in the existing FERC license. For the purposes of this document, the Project Area is defined as the area within the FERC Project Boundary and the land immediately surrounding the FERC Project Boundary (i.e., within about 0.25 mile of the FERC Project Boundary) and includes Project-affected reaches between facilities and downstream to the next major water controlling feature or structure, USACE s Daguerre Point Dam. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

209 reflecting YRDP operations and facilities since construction was completed in The hydrologic analysis is provided for the following four locations: North Yuba River at New Bullards Bar Dam site Middle Yuba River at its confluence with the North Yuba River South Yuba River at its confluence with the Yuba River Yuba River at Smartsville Figure shows the Project Area tributary reaches and the major tributary inflows (listed in blue boxes) and locations where tributary accretions are calculated (listed in black boxes) as used in hydrologic analysis. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-5

210 Source: MWH Americas, Inc. Figure YRDP Project Area Tributary Reaches Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

211 1.3 Water Year Types Several hydrologic indices are used to characterize the hydrology of the Yuba River. The YRI, which is incorporated into SWRCB Order Revised Decision 1644 (RD-1644), and the NYI, which is incorporated into the Lower Yuba River Accord (Yuba Accord), are used to determine the governing flow requirement in the lower Yuba River for their respective criteria Yuba River Index The YRI was developed in 2000 for the SWRCB Lower Yuba River Hearings to describe the hydrology of the lower Yuba River. This index is a measure of the unimpaired river flows at Smartsville. The YRI was used to determine the water year types and the corresponding instream flow requirements under SWRCB RD-1644 (SWRCB 2003). The YRI is determined by applying weighting factors to runoff from different periods of the year as follows: where: YRI previous = YRI of previous year (maximum 1,400); R winter = October through March unimpaired runoff at Smartsville; and R summer = April through July unimpaired runoff at Smartsville. YRI year types are determined as follows: Wet YRI greater than or equal to 1,230 TAF Above Normal YRI greater than or equal to 990 TAF Below Normal YRI greater than or equal to 790 TAF Dry YRI greater than or equal to 540 TAF Critical YRI less than 540 TAF Since the YRI is based on unimpaired flows, year-type definitions can be calculated from historical data. Table shows historical YRI year-types since the YRDP began operations. Table Historical Yuba River Index Year-Types 1970 to Water Year 1970 Wet 1971 Wet 1972 Below Normal 1973 Above Normal 1974 Wet YRI Year Type Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-7

212 Table (continued) Water Year 1975 Wet 1976 Critical 1977 Critical 1978 Above Normal 1979 Below Normal 1980 Wet 1981 Dry 1982 Wet 1983 Wet 1984 Wet 1985 Below Normal 1986 Wet 1987 Critical 1988 Critical 1989 Below Normal 1990 Dry 1991 Critical 1992 Critical 1993 Above Normal 1994 Critical 1995 Wet 1996 Wet 1997 Wet 1998 Wet 1999 Wet 2000 Above Normal 2001 Critical 2002 Critical 2003 Above Normal 2004 Below Normal 2005 Above Normal 2006 Wet 2007 Dry 2008 Critical 2009 Below Normal 2010 Below Normal 2011 Wet Key: YRI Yuba River Index YRI Year Type North Yuba Index The NYI was developed for the Yuba Accord (YCWA 2007). This index provides a measure of available water in the North Yuba River that can be used to meet instream flow requirements and delivery requirements to member units on the lower Yuba River (since the YRI is based on unimpaired flows at Smartsville, including flows from the Middle and South Yuba rivers, it does not accurately represent the water available for storage by YCWA). The NYI comprises two components: (1) active storage in NBB at the start of the current water year (October 1), and (2) total actual and projected inflow into NBB for the current water year, including diversions from the Middle Yuba River and Oregon Creek to NBB. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

213 The NYI is determined by adding the previous year s end-of-september active storage (storage greater than the FERC license minimum pool of 234 TAF) to the sum of actual and predicted inflows to NBB for the water year. NYI schedules are numbered 1 through 6 as indicators of specific hydrologic conditions to assign a flow requirement. A seventh schedule, which applies during the driest conditions, is called a Conference Year. The NYI values corresponding to the schedules from wettest to driest are as follows: Schedule 1: NYI greater than 1,400 TAF Schedule 2: NYI greater than 1,050 TAF Schedule 3: NYI greater than 930 TAF Schedule 4: NYI greater than 825 TAF Schedule 5: NYI greater than 690 TAF Schedule 6: NYI greater than 500 TAF Conference Year: NYI less than 500 TAF Conference Year conditions apply to determine the required instream flows during an extremely dry year occurrence. The Conference Year provisions of the Yuba Accord include specified minimum daily flows and a set of conditions for further determining flows in the lower Yuba River. Current project operations use the NYI to determine minimum flow requirements on the lower Yuba River. Since the NYI is partially a result of Yuba Project operations, it is not appropriate to compute the NYI for periods prior to the implementation of the Yuba Accord. Table shows the NYI Schedules since the implementation of the Yuba Accord Table North Yuba Index Values and Schedules from 2008 through Water Year NYI Value NYI Schedule , , , ,365 1 Key: NYI North Yuba Index Note: NYI Value represents the final index value based on California Department of Water Resources final Bulletin 120 update of the year. 2.0 Major Tributary flows This section describes flows from the upper Yuba River watershed to gaging locations on major reaches tributary to the Project Area. Flows in the Yuba River and its tributaries have been gaged by several agencies for varying lengths of time. Generally, a reliable mean daily flow record for major watershed streams exists from 1969 to the present day. Given the availability and reliability of these gaged flow data, flow measurements for the period of record (POR) of October 1969 through September 2008 were selected for inclusion in the compiled hydrologic data set for inflows to the YRDP Project Area. Since the U. S. Geological Survey (USGS) annually verifies the data recorded at its gages and USGS gage data are available throughout the Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-9

214 selected POR, data from USGS gages on each of the major watershed tributaries were selected for the hydrologic data set. All USGS gage data was acquired from the USGS National Water Information System (USGS 2011). USGS gages used for the hydrologic data set of flows are described in Table Not all listed gages are currently monitored. Figure shows the network of USGS gages in the vicinity of the Project; not all gages shown were used for the hydrologic data set. Table USGS Gages Used to Determine Major Tributary Flows Gage Number Tributary Period of Record Gage Name North Yuba River 10/1/30-Present North Yuba River Below Goodyears Bar Slate Creek 10/1/60-Present Slate Creek Below Diversion Dam, Near Strawberry Valley Oregon Creek 10/1/67-9/30/00 Oregon Creek At Camptonville Oregon Creek 10/1/88-Present Camptonville Tunnel At Intake, Near Camptonville Oregon Creek 9/1/68-Present Oregon Creek Below Log Cabin Dam, Near Camptonville Middle Yuba River 8/18/67-9/30/89 Middle Yuba River Near Camptonville Middle Yuba River 10/1/88-Present Lohman Ridge Tunnel At Intake, Near Camptonville Middle Yuba River 10/1/68-Present Middle Yuba River Below Our House Dam, Near Camptonville South Yuba River 10/1/40-Present South Yuba River At Jones Bar, Near Grass Valley Deer Creek 10/1/35-Present Deer Creek Near Smartsville Yuba River 10/1/41-Present Yuba River Below Englebright Dam, Near Smartsville Yuba River 10/1/43-Present Yuba River Near Marysville Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

215 Figure Schematic of Lower Yuba River USGS Gage Network Hydrologic analysis relied on gages listed in Table along with the synthesis of local accretions 4 to key subbasin locations from ungaged tributaries, as described in Section 3, to complete the data set. The synthesis of accretions is needed for intermediate locations within the project area to provide a detailed, accurate flow record for YRDP facility locations. Gages were selected for this analysis based on their locations in the stream network, and the period of record of available historical data for the gage. Historical gage data can be found in Attachment 2-2E, the Hydrology CD. 4 The term accretions is used in this document to mean runoff to a stream that is below a gaging point; therefore is not directly measured and must be determined through some other hydrologic analysis method. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-11

216 2.1 North Yuba River The upper extent of the North Yuba River is at Yuba Pass (elevation 6,701 feet msl) near State Highway 49 in Sierra County. The river flows parallel to the state highway as far as Downieville, where it diverges from the highway and flows westward into NBB. The North Yuba River terminates at its confluence with the Middle Yuba River, approximately 2 miles downstream from New Bullards Bar Dam, at which point the combined flow of the two rivers becomes the Yuba River. The total area of the North Yuba River watershed is approximately 491 square miles and includes portions of Yuba, Sierra, and Plumas counties. The record of daily flow data from the primary gage in the watershed, Goodyears Bar (USGS Gage ) at approximately 2,453 feet msl, extends from October 1, 1930 through the present and represents drainage from a watershed area of approximately 250 square miles. There are no major impairments on the North Yuba River above Goodyears Bar that substantially affect river flow. Canyon Creek, an ungaged tributary to the North Yuba River, with a subbasin of approximately 61 square miles, flows into the North Yuba River approximately 8 miles downstream from Goodyears Bar. Similar to the North Yuba River subbasin above Goodyears Bar, the Canyon Creek subbasin is predominantly snowmelt-fed and has no upstream impairments. Slate Creek, discussed in Section 2.2, flows into the North Yuba River approximately 12 miles below Goodyears Bar. A smaller tributary, Deadwood Creek, joins the North Yuba River approximately 0.5 miles below Slate Creek. The Deadwood Creek subbasin is approximately 6.7 square miles and is relatively low in elevation; accordingly, it is mainly a rainfall-fed subbasin. Flows are gaged at a small hydropower plant on the creek, the Deadwood Creek Plant (USGS Gage ), which has a gage record from October 1, 1994, through the present. Figure shows a schematic of the North Yuba River and its primary tributaries. Figure Gage Network of the North Yuba River The North Yuba River subbasin is a predominantly snowmelt-fed stream, with peak flows occurring from March through May. On a long-term average basis, North Yuba River flows are Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

217 lowest from August through October. Average monthly North Yuba River flows at Goodyears Bar are shown in Table Table Historical Average Monthly North Yuba River Flow at Goodyears Bar. Location Average 2 Monthly Inflow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) North Yuba River Inflow ,225 1,311 1,766 1, Notes: 1 North Yuba River below Goodyears Bar flow from USGS Gage Period of record is 10/1/1969-9/30/2010 Key: cfs = cubic feet per second TAF = thousand acre-feet USGS=U.S. Geological Survey 2.2 Slate Creek Slate Creek originates near the town of La Porte, in the northern portion of the Yuba River watershed. The Slate Creek subbasin is approximately 61 square miles. SFWPA diverts flows from Slate Creek into the Feather River Basin near Strawberry Valley via the Slate Creek Tunnel at approximately 3,500 feet msl. Approximately 49 square miles of the Slate Creek subbasin is above the Slate Creek Tunnel. The Slate Creek Tunnel has a maximum capacity of 848 cubic feet per second (cfs), and its flow has been measured at USGS Gage since October 1, Slate Creek joins the North Yuba River approximately 0.5 miles upstream from the normal high water mark of NBB. Slate Creek flows have been continuously gaged below the Slate Creek Tunnel by USGS Gage since October 1, Figure shows the gage network on Slate Creek. Figure Gage Network of Slate Creek flows to New Bullards Bar Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-13

218 Similar to the North Yuba River subbasin, the Slate Creek subbasin above the Slate Creek Tunnel, as measured at USGS Gage , is predominantly snowmelt-fed. Peak flows on Slate Creek generally occur from January through March, and low flows generally occur between July and September. Peak diversions to the Feather River Basin through the Slate Creek Tunnel typically occur in March and May, and the average annual diversion since 1962 is approximately 74 TAF. Before 1985, SFWPA diverted Slate Creek flows year around, but diversions since 1985 have typically been limited to December through June. The average annual diversion since 1985 is 68 TAF per year. Slate Creek flows below the Slate Creek Diversion Dam are determined from the historical records at the Slate Creek gage, USGS Gage Average monthly flows at this gage are shown in Table Table Historical Average Monthly Slate Creek Flows below the Slate Creek Tunnel. Location Average 1 Monthly Inflow (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Slate Creek Inflow Notes: 1 Period of record: 10/1/1969-9/30/ Slate Creek below Diversion Dam flow from USGS Gage Key: cfs=cubic feet per second TAF = Thousand acre-feet USGS=U.S. Geological Survey 2.3 Middle Yuba River Flows in the Middle Yuba originate from snowmelt and rainfall runoffs above the largest upper watershed impoundment, Jackson Meadows Reservoir, with a dam crest of elevation 6,044.5 feet msl, in Sierra County. Most of the upper Middle Yuba River is confined by narrow, steep canyons which continue downstream to the 75-foot-high Our House Dam, the upper extent of the YRDP on the Middle Yuba River, located southwest of Camptonville near the Sierra/Nevada County line. Approximately 12 miles below Our House Dam, the Middle Yuba River joins the North Yuba River to form the Yuba River. The Middle Yuba River watershed, including its major tributary Oregon Creek, covers approximately 210 square miles, with elevations ranging from 1,120 feet msl to 7,200 feet msl. There are several impairments on the upper Middle Yuba River that are part of the NID Yuba- Bear Project (FERC Project No. 2266). A portion of Middle Yuba River flows are diverted into the South Yuba River subbasin through the Yuba-Bear Project s Milton-Bowman Tunnel at NID s Milton Diversion Dam. The Yuba-Bear Project is operated to meet minimum Middle Yuba River in-stream flow requirements below the Milton Diversion Dam. Releases from the Milton Diversion Dam and runoff from the area below the dam flow to Our House Dam at crest elevation 2,030 feet msl. Inflow at Our House Dam is partially diverted to Oregon Creek through the Lohman Ridge Tunnel. Oregon Creek joins the Middle Yuba River approximately 8.5 miles below Our House Dam, and the Middle Yuba River joins the North Yuba River below NBB to form the Yuba River. Approximately 23 square miles of the Middle Yuba River watershed lie below Our House Dam. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

219 Inflow to Our House Dam from the Middle Yuba River is determined from three gages. Before 1989, USGS Gage recorded Middle Yuba River flows approximately 3.25 miles above the Dam, near Camptonville. Since 1989, Middle Yuba inflows to the Our House Dam are determined by adding the flow below Our House Dam, measured at USGS Gage , to Lohman Ridge Tunnel flows, measured at USGS Gage Figure shows the gage network for the Middle Yuba River around Our House Dam. Figure Gage Network of Middle Yuba River around Our House Dam Using the methodology described above to compute the inflow to this location, a continuous record of daily data from October 1, 1969 to September 30, 2010 was computed. Since the watershed contributing to USGS Gage is slightly smaller than USGS Gage (136 square miles for USGS Gage compared to 145 square miles for USGS Gage ), flows were assumed to be directly proportional to the size of the watershed so flows from USGS Gage were increased by the factor of 145/136. Computed average monthly inflows to Our House Dam are shown in Table Table Historical Average Monthly Middle Yuba River Flows above Our House Dam. Location Average Monthly Inflow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) Middle Yuba River Inflow Notes: 1 Middle Yuba River above Our House Dam flow from: USGS Gage * 145/136 (10/1/1969 through 9/30/1989) USGS Gages (10/1/1989 through 9/30/2010) Key: cfs = cubic feet per second TAF = Thousand acre-feet USGS=U.S. Geological Survey 2.4 South Yuba River The headwaters of the South Yuba River originate at elevation 9,000 feet msl in Placer County near Castle Peak and Donner Lake. The South Yuba River is subject to multiple upstream Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-15

220 impairments before it joins the Yuba River in Englebright Reservoir. Primary upstream impairments are NID s Yuba-Bear Project (FERC Project No. 2266), and PG&E s Drum- Spaulding Project (FERC Project No. 2310). Flow from the Middle Yuba River is diverted to the South Yuba River via the Milton-Bowman Tunnel to Bowman Reservoir and then through the Bowman-Spaulding Tunnel to Lake Spaulding. Flow from the South Yuba River is diverted into the Bear and American river basins via the Drum Canal and South Yuba Canal. Remaining South Yuba River flow joins the Yuba River in Englebright Reservoir. Flows on the lower South Yuba River have been continuously measured at Jones Bar gage (USGS Gage ), located approximately 7 miles upstream from the confluence of the Yuba River and South Yuba River, since April 1, Of the approximately 352-square-mile South Yuba River watershed, approximately 42 square miles lie below Jones Bar gage. Figure shows the gage network of the lower South Yuba River. Figure Gage Network of the Lower South Yuba River Flows from the upper reaches of the South Yuba River are determined from historical daily flow data measured at Jones Bar gage (USGS Gage ) from October 1, 1969 through September 30, Average annual South Yuba River flow at this location is approximately 312 TAF, with peak flows occurring from April through June, corresponding to the snowmelt season. Low flows on the South Yuba River generally occur from July through mid-december. Table shows the historical average monthly flow from the South Yuba River, measured at Jones Bar gage. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

221 Table Historical Average Monthly South Yuba River Flows at Jones Bar. Yuba County Water Agency Location Average 1 Monthly Inflow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) South Yuba River Inflow Notes: 1 Period of Record: 10/1/1969 through 9/30/ South Yuba River at Jones Bar flow from USGS Gage Key: cfs = cubic feet per second TAF = Thousand acre-feet USGS=U.S. Geological Survey 2.5 Oregon Creek Oregon Creek is entirely contained within the Middle Yuba River watershed, and originates near elevation 4,455 feet msl. Log Cabin Dam, a 55-foot-high dam, diverts flows from Oregon Creek to NBB through the Camptonville Tunnel. Log Cabin Dam is approximately 4 miles upstream from Oregon Creek s confluence with the Middle Yuba River. Oregon Creek flow above Log Cabin Dam is a combination of outflow from the Lohman Ridge Tunnel, originating at Our House Dam on the Middle Yuba River, and Oregon Creek flow. Above the outfall of the Lohman Ridge Tunnel, Oregon Creek is free of impairments. As a result, it is a useful index watershed for characterizing rainfall runoff to compute accretions in other similar watersheds. Of the approximately 35 square miles of the Oregon Creek watershed, about 6 square miles lie below Log Cabin Dam. Between October 1, 1968 and September 30, 2000, Oregon Creek flows to Log Cabin Dam were gaged by USGS Gage , located approximately 1.5 miles upstream of the Lohman Ridge Tunnel outfall. Since September 2000, Oregon Creek flows to Log Cabin Dam are calculated by adding flows below Log Cabin Dam, measured by USGS Gage , to Camptonville Tunnel flows, measured by USGS Gage , and subtracting Lohman Ridge Tunnel flows, measured at USGS Gage Figure shows the gage network for Oregon Creek. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-17

222 Figure Gage Network of Oregon Creek above Log Cabin Dam Using the methodology described above, Oregon Creek flows from October 1, 1969 through September 30, 2010 were computed; however, in some periods, gaging errors resulted in obviously incorrect values, such as negative or very large values. These errors were manually corrected for periods shown in Table Since the watershed contributing to USGS Gage is slightly smaller than USGS Gage (23 square miles for USGS Gage compared to 29.1 square miles for USGS Gage ), flows were assumed to be directly proportional to the size of the watershed so flows from USGS Gage were increased by the factor of 29.1/23. Table Corrections to Computed Historical Oregon Creek Flows above Log Cabin Dam. Date Original Revised Value (cfs) Value (cfs) Rationale 11/21/ Replaced with previous day s value 11/28/ Replaced with previous day s value 11/29/ Replaced with previous day s value 11/07/ Replaced with previous day s value 06/30/ Replaced with previous day s value 07/01/ Replaced with previous day s value 7/15-8/2/2003 Varied 2.0 Used previous year s corresponding flow 6/1-6/4/2004 Varied 9.0 Used previous year s corresponding base flow 10/17/ Replaced with previous day s value 10/19/ Replaced with previous day s value 11/03/ Replaced with previous day s value 01/14/ Replace with average of surrounding days 5/19/2005 1, Corrected obvious Lohman Ridge Tunnel flow error 6/19-7/18/2006 Varied Varied Replaced with historic 2000 receding flows 4/3-4/21/2007 Varied Varied Replaced with historic 1989 receding flows Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

223 Table (continued) Yuba County Water Agency Date Original Revised Value (cfs) Value (cfs) Rationale 5/15-5/29/2007 Varied Varied Replaced with historic 1991 receding flows 5/27/ Replaced with previous day s value 5/30-6/8/2008 Varied 4.00 Replaced with recent flow trend 9/30/ Replaced with previous day s value 10/14/ Slight increase over previous day 10/21/ Average of surrounding days Key: cfs = cubic feet per second Oregon Creek is a rainfall-dominated basin: peak flows occur from January through May, and low flows occur from June through November. Table shows the historical average monthly Oregon Creek inflow. Table Historical Average Monthly Oregon Creek Flows above Log Cabin Dam. Location Average Monthly Inflow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) Oregon Creek Inflow 1 Notes: 1 Oregon Creek above Log Cabin Dam flow from: USGS Gage * 29.1/23 (10/1/1969 through 9/30/2000) USGS Gages (10/1/2000 through 9/30/2010) Key: cfs = cubic feet per second TAF = Thousand acre-feet USGS=U.S. Geological Survey 2.6 Deer Creek Deer Creek originates in Nevada County, and in addition to natural runoff, receives flows from the South Yuba River by way of PG&E s Drum-Spaulding Project. The approximately 89- square-mile Deer Creek watershed is primarily rainfall-fed; its natural flows are augmented by diversions from the South Yuba River via the South Yuba Canal. Several canals divert flow from Deer Creek to the Bear River watershed. Deer Creek is subject to impoundment in NID s Scotts Flat Reservoir and in Lake Wildwood before it flows into the Yuba River near Smartsville, below Englebright Reservoir. Historical Deer Creek flows near Smartsville have been measured since October 1, 1935 at USGS Gage , approximately 1 mile upstream from the confluence of Deer Creek with the Yuba River. The watershed contributing to Deer Creek flow below the Deer Creek gage is approximately 5 square miles, and is discussed in Section 3.3. Figure shows the gage network for Deer Creek near Smartsville. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-19

224 Figure Gage Network of Deer Creek Flow near Smartsville. As a result of upstream impairments to Deer Creek, its inflows to the Yuba River do not follow a natural streamflow hydrograph. Peak flows typically occur from December through April, and low flows typically occur from June through October. Table shows average historical monthly Deer Creek flow at the Deer Creek gage. Table Historical Average Monthly Deer Creek Flows near Smartsville. Location Average 1 Monthly Inflow (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Deer Creek Inflow Notes: 1 Period of Record: 10/1/1969 through 9/30/ Deer Creek near Smartsville flow from USGS Gage Key: cfs=cubic feet per second TAF=thousand acre-feet USGS=U.S. Geological Survey 3.0 Ungaged Accretions This section describes accretions to New Bullards Bar Reservoir, Englebright Reservoir, the lower Yuba River, and Dry Creek below the locations described in Section 2 to complete the calculation of inflows to the Project Area. While the majority of the tributaries to the Yuba River are gaged, there is a considerable amount of inflow to the Yuba River not directly gaged by streamflow measurement. Using the methodologies discussed below, ungaged accretions are computed for all Project Reaches below the major tributary inflows discussed in Section 2. Without direct streamflow gage data, several methods were examined to estimate accretions. Methodologies examined to compute accretions included the following: Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

225 1. Computation of accretions using a simple mass balance equation. This method consists of subtracting the volume of periodic flow at a measured upstream location from a measured downstream location to determine the volume of intervening additional flow. 2. Computation of accretions using statistical regressions. This method consists of using statistical methods to determine a numerical relationship between a watershed with known characteristics and measured flows and the area of interest. 3. Computation of accretions using - area-weighted scaling of a known, comparable watershed flow and applying a precipitation-based adjustment. This method consists of multiplying known flows of one watershed with similar physical characteristics by the ratio of the area and precipitation of the watershed with measured flows to the area and precipitation of the watershed of interest. After an analysis of the accuracy of the three methods for computation of inflows to New Bullards Bar Reservoir, the area-weighted scaling methodology was determined to be the most applicable to the Yuba River subbasin accretions. Figure shows the Yuba River watershed and the subbasins included in analysis. Similarly, Figure shows the Yuba River watershed and the average annual precipitation for each subbasin based on a 30-year average, computed on a 4-kilometer grid by the Parameter-Elevation Regressions on Independent Slopes Model (PRISM). Subbasin accretions are described based on their location within the subbasin; North Yuba River, Slate Creek, and Canyon Creek accretions are included in the discussion of NBB accretions; Oregon Creek, Middle Yuba River, South Yuba River, and Yuba River accretions are included in the discussion of Englebright accretions; and Dry and Deer Creek and lower Yuba River accretions are included in the lower Yuba River accretions discussion. All of the calculations used to compute the ungaged accretions, and the resulting timeseries can be found in Attachment 2-2E, the Hydrology CD. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-21

226 Source: MWH Americas, Inc. Figure Yuba River Watershed and Subbasins Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

227 Source: MWH Americas, Inc. Figure Yuba River Watershed and Subbasin Average Annual Precipitation Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-23

228 3.1 Accretions to New Bullards Bar Reservoir As previously discussed, New Bullards Bar Reservoir receives inflows from several tributaries, including the largely unimpaired mainstem North Yuba River as well as its primary tributaries, Slate Creek, Canyon Creek, and Deadwood Creek. While Canyon Creek and Deadwood Creek are essentially unimpaired, SFWPA diverts from Slate Creek into the Feather River watershed. The North Yuba River watershed is generally snowmelt-dominated at higher elevations and rainfall-dominated at lower elevations, as shown in Table Table New Bullards Bar Reservoir Tributaries. Subbasin Area (square miles) Average Annual Precipitation (inches) Major Source North Yuba River above Goodyears Bar snow Slate Creek above the Slate Creek gage snow Canyon Creek snow North Yuba River between Goodyears Bar and Slate Creek rain North Yuba River between Slate Creek and New Bullards Bar Dam rain Slate Creek below Slate Creek gage rain Deadwood Creek rain Total Although there are gages on the upper North Yuba River and upper Slate Creek, the lower reaches of these two tributaries, Canyon Creek, and Deadwood Creek, are ungaged. Table includes some information about NBB tributaries. As shown in Table 3.1-1, the total area of watershed above NBB is square miles. Of this area, 190 square miles or 39 percent is not directly measured by streamflow gage and makes up the accretion area to be synthesized. Three methods of calculating the accretions to NBB were completed. These methods are described in the following sections. One of these methods, the area-weighted scaling method was selected as the best method for accurately calculating daily flow for the POR Calculation of Accretions to New Bullards Bar Reservoir Using Mass Balance Methodology Total daily accretion flow to NBB is calculated using a simple reservoir mass balance equation: The components of this equation were defined as follows: NBB storage = daily New Bullards Bar Reservoir storage change (USGS Gage ) NBB releases = sum of the following daily flows: o NBB releases to the Colgate Tunnel (USGS Gage ) Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

229 o NBB minimum flow releases, spills and other releases (USGS Gage and data from YCWA gages) NBB gaged inflows = sum of the following daily flows: o North Yuba River above Goodyears Bar (USGS Gage ) o Slate Creek above Slate Creek gage (USGS Gage ) o Camptonville Tunnel (USGS Gage from 1988 to present; calculated using USGS Gages and on Oregon Creek, on the Lohman Ridge Tunnel, and and on the Middle Yuba River from 1969 to 1988) Storage in NBB is calculated by measuring the water surface elevation in the reservoir and converting this to a storage value by using an elevation-versus-storage table that has been established for the reservoir. Although the elevation measurement is made to within one hundredth of a foot, the large surface area of the reservoir makes the daily variation of this measurement rather large and results in a highly variable accretion flow value. To facilitate accretions calculations, total daily accretions were smoothed using 7-day average data for reservoir storage, total inflows, and total releases. 5 However, even using the centered 7-day average data resulted in the calculation of many accretions that were below zero. Given that the Yuba River above the Reservoir and its tributaries are believed to comprise of mostly accretions, it is not likely that seepage losses to groundwater have a large influence on ungaged flows above New Bullards Bar which would be the mechanism that could result in negative values. Therefore, the result of negative accretions is most likely due to the accumulation of data errors. Possible errors in the data used in the accretions calculation include: Error in the reservoir stage data used to calculate reservoir storage due to wind or other factors that make the stage measurement inconsistent; Measurement error of NBB non-spill releases due to location of the NBB gage close to the dam outlet, where turbulent flow may occur; Measurement error of NBB spill releases; and/or Measurement error at each USGS gage Estimation of Accretions to New Bullards Bar Reservoir Using Statistical Regression Methodology NBB accretions were also estimated using the following linear regression, including terms for both snowmelt- and rainfall-dominated watersheds: 5 Smoothing was also attempted using a running 7-day average, but it did not smooth as well as the centered average. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-25

230 In this regression, the snow and rain index flows were the daily flows on the North Yuba River at Goodyears Bar and on Oregon Creek above Log Cabin Dam, respectively. Using the Solver tool in Microsoft Excel, the coefficients x and y were computed to minimize the difference between the calculated NBB accretions and the NBB accretions estimated by the linear regression. The coefficients were optimized as the following: x = 0.26; and y = These coefficients suggest that NBB accretions consist of one part snow to 16 parts rain, which is in agreement with the fact that most ungaged flows above the reservoir occur at relatively lower elevations in the watershed, which are typically rainfall-driven. This method provided reasonable results for all time periods Estimation of Accretions to New Bullards Bar Reservoir using Area- Weighted Flow Methodology The USGS proposes the following area-weighted relationship between ungaged and gaged flows (Q), drainage areas (A), and Precipitation (P) within a single watershed (USGS 2007): This equation is applied to the North Yuba River watershed by including components for both the snowmelt- and rainfall-dominated parts of the watershed: To solve for accretions to NBB (Q ungaged ), the upper North Yuba River subbasin above Goodyears Bar was chosen as the index snowmelt-dominated gaged watershed because of the following: The majority of its annual flow volume originates as snowmelt; Its flows are unimpaired by storage reservoirs or diversion dams; It is the largest unimpaired watershed above NBB; and Its gage has a long POR (1930 to present). Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

231 Although it is not part of the North Yuba River watershed and its flows do not contribute to NBB storage, the upper Oregon Creek watershed was chosen as the index rainfall-dominated gaged watershed for the following reasons: Its flows are rainfall-dominated (most of the watershed is below 5,000 feet msl); It is unimpaired by upstream dams or reservoirs; and Flow data is available for the POR of analysis (1969 to present). Given these two index watersheds, the snowmelt- and rainfall-dominated gaged areas and flows were defined as follows: A gaged,snow = area of the North Yuba River watershed above Goodyears Bar; Q gaged,snow = flows on the North Yuba River at Goodyears Bar (at USGS Gage ); P gaged, snow = average annual precipitation of the North Yuba River watershed above Goodyears Bar; A gaged,rain = area of the Oregon Creek watershed above Log Cabin Dam; Q gaged,rain = flows on Oregon Creek above Log Cabin Dam (calculated using USGS Gage from 1969 to 2000; using USGS Gages , , and from 2000 to present); and P gaged, rain = average annual precipitation of the Oregon Creek watershed above Log Cabin Dam. The total gaged and ungaged snowmelt- and rainfall-dominated areas and precipitations are shown in Table The total ungaged snowmelt-dominated area above NBB (A ungaged,snow ) is defined as the area of the Canyon Creek watershed. The total ungaged rainfall-dominated area above NBB (A ungaged,rain ) is defined as the sum of the following watershed areas: North Yuba River between Slate Creek and Goodyears Bar (USGS Gage ); North Yuba River between Slate Creek and New Bullards Bar Dam; Slate Creek below Slate Creek gage (USGS Gage ); and Deadwood Creek. The ratio of the area and precipitation of the Canyon Creek subbasin to the area and precipitation of the North Yuba River above Goodyears Bar is The ratio of the area and precipitation of ungaged rainfall-dominated basins to the area and precipitation of the Oregon Creek above Log Cabin Dam subbasin is These two ratios were multiplied by the daily flows from the Goodyears Bar gage and Oregon Creek above Log Cabin Dam, respectively, to compute accretions to the subbasin above New Bullards Bar Dam for the POR. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-27

232 3.1.4 Comparison of Accretions Calculation and Estimations Comparing accretions from the statistical regression and area-weighted flow methodologies with those from the mass balance methodology showed the two estimation methods were well correlated with the mass balance method. A comparison of the coefficients for North Yuba River flow at Goodyears Bar and Oregon Creek above Log Cabin indicate the area-weighted methodology yields very similar values to those determined through a statistical analysis. Comparing the accumulated flow volumes of the area-weighted flow method and the mass balance method indicates a consistent comparison of the two methods through time. Figure shows the accumulated mass plot comparing the two methods indicating the two methods result in a similar volume of accretion over the full period of record. Since the area-weighted flow methodology is a published approach, and represents hydrologic processes rather than a mathematical solution, it was selected as the most appropriate methodology to estimate accretions to the North Yuba River above New Bullards Bar Dam. Figure Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to New Bullards Bar Reservoir An assessment of potential gaging error showed that application of a small variance in the Colgate Powerhouse gage (USGS ) readings, as shown in Table 3.1-2, would improve Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

233 the overall alignment of the area-weighted flow accumulated volume with the mass balancebased approach. Figure shows the comparison of the accumulated volumes with the adjustment to the Colgate Powerhouse gage. Table Applied Colgate Powerhouse Gage Correction Factors Period (Water Year) Factor % % % % Figure Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to New Bullards Bar Reservoir with Colgate Powerhouse Gage Correction This correction suggests differences between methods for computing accretions can be explained by potential small gaging errors. Similarly, this indicates the area-weighted flow method described in Section can successfully be used to compute accretions within acceptable ranges of gaging error. It should be noted that the review of gage error is used to demonstrate the area-weighted flow method attains similar results as the mass-balance method, as shown in Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-29

234 Figure 3.1.2, when a fairly small gage correction factor is applied. It is not implied that there is error in the USGS gages, rather that differences between the two methodologies are within reasonable amounts. No adjustments are proposed to the area-weighed method results to compute the final accretions beyond the calculation described in Section Computation of Ungaged Accretions to North Yuba River above New Bullards Bar Dam Subbasins Using the area-weighted flow methodology described above, accretions to the North Yuba River above New Bullards Bar Dam can be computed at a subbasin scale. The watershed of the North Yuba River above New Bullards Bar Dam can be divided into several smaller ungaged subbasins. Comparing the areas of the subbasins with an index watershed, and multiplying the index watershed flow by the ratio of their areas and precipitations yields the contribution of that subbasin to the total ungaged accretions from the North Yuba River above New Bullards Bar Dam. Since it is so small, Deadwood Creek is included in the North Yuba River between Slate Creek and New Bullards Bar Dam calculation. Table shows these subbasins, their areas, average annual precipitations, and their index watersheds. Table Ungaged North Yuba River above New Bullards Bar Dam Subbasins. Subbasin Area (Square Miles) Average Annual Precipitation (inches) Index Watershed Area-Weighting Ratio North Yuba River between Oregon Creek above Log Cabin Goodyears Bar and Slate Creek Dam 1.46 Canyon Creek North Yuba River above Goodyears Bar 0.28 Slate Creek Below Slate Creek Gage Oregon Creek above Log Cabin Dam 0.45 North Yuba River between Slate Oregon Creek above Log Cabin Creek and New Bullards Bar Dam Dam 2.50 Total Area Indexing Oregon Creek Total Area Indexing North Yuba River Total Ungaged Area To confirm all areas were accounted for, subbasin accretions were compared with total ungaged North Yuba River accretions above New Bullards Bar Dam. The total accretion value for all subbasins agreed with the North Yuba River accretion value. Figure shows the subbasins used to determine ungaged accretions. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

235 Source: MWH Americas, Inc. Figure Yuba River Ungaged Accretion Subbasins Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-31

236 North Yuba River Accretions Accretions were computed for the North Yuba River between Goodyears Bar and Slate Creek using the methodology described above, comparing the area and precipitation of the North Yuba River subbasin between Goodyears Bar and Slate Creek with the area, precipitation and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to the North Yuba River between Goodyears Bar and Slate Creek. Table Computed Monthly Average Accretions to the North Yuba River between Goodyears Bar and Slate Creek. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) North Yuba River Accretions Notes: 1 Period of Record: 10/1/1969 through 9/30/ North Yuba River below Goodyears Bar accretions computed for the reach between Goodyears Bar and Slate Creek using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Canyon Creek Accretions Accretions were computed for Canyon Creek using the methodology described above, comparing the area of the Canyon Creek subbasin with the area and flow of the North Yuba River above Goodyears Bar. Table shows the computed monthly average accretions to the Canyon Creek. Table Computed Monthly Average Accretions to Canyon Creek. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Canyon Creek Accretions Notes: 1 Period of Record: 10/1/1969 through 9/30/ Canyon Creek accretions computed using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Slate Creek Accretions Accretions were computed for Slate Creek for the reach between the Slate Creek Diversion Dam and Slate Creek s confluence with the North Yuba River using the methodology described above, comparing the area of the subbasin contributing to Slate Creek between the Slate Creek Diversion Dam and Slate Creek s confluence with the North Yuba River with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to Slate Creek between the Slate Creek Diversion Dam and the Slate Creek s confluence with the North Yuba River. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

237 Table Computed Monthly Average Accretions to Slate Creek between the Slate Creek Diversion Dam and Slate Creek s Confluence with the North Yuba River. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Slate Creek Accretions Notes: 1 Period of Record: 10/1/1969 through 9/30/ Slate Creek below Slate Creek Diversion Dam accretions computed for the reach between the Slate Creek Diversion Dam and Slate Creek s confluence with the North Yuba River using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Accretions to New Bullards Bar Reservoir Accretions were computed for the subbasin contributing to inflows directly to NBB and the North Yuba River below the Slate Creek confluence using the methodology described above, comparing the area of the subbasin contributing to NBB with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to NBB. Table Computed Monthly Average Accretions New Bullards Bar Reservoir. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Accretions to New Bullards Bar Reservoir 2 Notes: 1 Period of Record: 10/1/1969 through 9/30/ New Bullards Bar Reservoir accretions computed for the area between the confluence of the North Yuba River and Slate Creek and New Bullards Bar Dam using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Computation of New Bullards Bar Reservoir Evaporation Evaporation from NBB is a notable factor in Yuba River hydrologic analysis. Since direct measurement of evaporation is impractical, quantification of evaporative losses from the reservoir relies upon previous analyses. As a part of the development of a USACE Hydrologic Engineering Center (HEC)-3 model, the California Department of Water Resources (DWR) developed a monthly pattern of evaporation for NBB. Table has the monthly evaporation rates from the HEC-3 model. Table Computed Monthly Evaporation Rates for New Bullards Bar Reservoir. Monthly Evaporation Rate (inches) Location Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep New Bullards Bar Reservoir Notes: From DWR HEC-3 Yuba River Watershed Model. January 1985 Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-33

238 Applying these reservoir evaporation rates to historical daily NBB water surface areas yields historical evaporation volumes. Table shows historical monthly average NBB evaporation, based on published evaporation rates. Table Computed Historical Monthly Average New Bullards Bar Reservoir Evaporation. Location Average 1 Monthly Evaporation (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) New Bullards Bar Reservoir Notes: 1 Period of Record: 10/1/1969 through 9/30/ New Bullards Bar Reservoir evaporation computed by multiplying reservoir evaporation rates from Table with historical reservoir water surface areas. Key: cfs = cubic feet per second TAF= thousand acre-feet 3.2 Accretions to Englebright Reservoir Accretions to Englebright Reservoir and the Yuba River below New Bullards Bar Dam contribute to the operations of Englebright Dam. Therefore, they need to be accounted for when determining flows within the Project Area. In a similar process to the one used to determine North Yuba River accretions to NBB, accretions to Englebright Reservoir were computed using a mass balance methodology, using change in storage and releases from Englebright Dam to compute total inflow to the reservoir. Local accretions were computed by subtracting known inflows from Oregon Creek and the Middle and South Yuba rivers. Changes in Englebright Reservoir elevation and storage are highly variable, since Englebright Reservoir is used as a regulating afterbay to NBB and the surface area of Englebright Reservoir is relatively small compared with flows from NBB releases. During normal operations, releases from Englebright Dam to the lower Yuba River are kept at a relatively consistent rate throughout a week, but releases from NBB are highly variable, reflecting changing release rates for power generation. Due to the high degree of daily and hourly variation of Englebright Reservoir storage, using daily storage values to compute accretions to Englebright Reservoir leads to extremely inconsistent values. In an effort to smooth accretions, a 7-day average storage, release, and gaged inflow was used to compute accretions to Englebright Reservoir: Englebright accretions = Englebright storage + Englebright releases Englebright gaged inflows The components of the mass balance were defined as follows: Englebright storage = daily storage Reservoir change data (data from YCWA) Englebright Dam releases = flow below Englebright Dam at Smartsville (data from USGS Gage ) Englebright Dam gaged inflows = sum of the following daily flows: o NBB minimum flow releases, spills and other releases (data from USGS Gage and YCWA gages) Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

239 o NBB releases to the Colgate Tunnel (data from USGS Gage ) o Oregon Creek above Log Cabin Dam (data from USGS Gage from 1969 to 2000; calculated using USGS Gages , , and from 2000 to present) o Middle Yuba River above Our House Dam (data from USGS Gage ) o South Yuba River at Jones Bar (data from USGS Gage ) Despite the use of the 7-day average for flows and storage, resulting accretions remain more variable than would be expected in a natural system. Accordingly, the area-weighted flow methodology validated for computing accretions to the North Yuba River above New Bullards Bar Dam is applied to compute Yuba River accretions above Englebright Dam. Due to the lower elevations of the ungaged basins tributary to the Yuba River above Englebright Dam, no snowmelt component is included; instead, only the rain-fall aspect of the methodology for the North Yuba River tributaries is used. Since NBB accretions estimated using an Oregon Creek index correlate well with the massbalance calculated NBB accretions, a similar assumption is used to compute accretions to Englebright Reservoir and the Oregon Creek watershed above Log Cabin Dam is used as the gaged index area having representative rainfall-dominated unimpaired flows. The ungaged area is defined as the sum of the areas summarized in Table Table Sources of Inflows to Englebright Reservoir. Subbasin Area Average Annual Area-Weighting (square miles) Precipitation (inches) Ratio North Yuba River below NBB Oregon Creek above Log Cabin Dam Gaged Oregon Creek below Log Cabin Dam Middle Yuba River above Our House Dam Gaged Middle Yuba River between Our House Dam and Oregon Creek Middle Yuba River below Oregon Creek South Yuba River above Jones Bar Gage Gaged South Yuba River below Jones Bar Gage Yuba River above Colgate Powerhouse Yuba River between Colgate Powerhouse and Englebright Dam Total Ungaged Area Comparison of Englebright Accretions Calculation and Estimation When comparing accretions determined through the mass-balance methodology with those determined using the area-weighted flow methodology, there is a notable disparity in accumulated volume. The lack of correlation between the area-weighted flow and mass-balance Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-35

240 method time series is likely due primarily to errors in the data used in the summation methodology as described above. Possible sources of error include: Error in the reservoir stage data used to calculate reservoir storage due to wind or other factors that make the stage measurement inconsistent; Measurement error of Englebright Dam non-spill releases due to location of the Englebright Dam gage close to the dam outlet, where turbulent flow may occur; Inaccurate gaging of Englebright Dam spill releases, especially because Englebright Dam spills often; and/or Measurement error of at each USGS gage, particularly the Colgate Powerhouse releases and the Smartsville gage. As shown in Figure 3.2-1, the difference in rate of accumulated volume between the two methodologies varies greatly in total and through time. This suggests a variable gage error through time. The assumed source of most of the differences between these two methods are gage errors associated with the Colgate Powerhouse and Smartsville gages used in the mass balance calculation. Since the volume of flow measured by these gages is significantly greater than the volume of flow otherwise calculated as an accretion, these two gages are the likely source of differences. For example, while the accumulated flow of the mass balance accretion totals approximately 3 MAF, the total flow measured at the Smartsville gage is about 67 MAF, or more than 20 times the amount of flow that is being evaluated. Therefore an error in gage measurement of 5% at the Smartsville gage, considered by the USGS to have a good stream gage rating, would result in as much as 3.35 MAF (5% of 67 MAF) of accumulated error. Using the Colgate Powerhouse correction factors described in Section 3.1.4, and identifying approximate errors of Smartsville gage flows according to obvious breakpoints, a substantially improved agreement between the two methodologies was reached. Figure shows the comparison of accumulated volume after applying the gage correction factors shown in Table Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

241 Figure Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to Englebright Reservoir Table Applied Smartsville Gage Correction Factors Period (Water Year) Correction % % % Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-37

242 Figure Comparison of Accumulated Volumes for Various Methodologies of Estimating Accretions to Englebright Reservoir with Gage Correction Factors As described in Section 3.1.4, this correction suggests differences between methods for computing accretions can be explained by potential small gaging errors. It is also reasonable to assume gage accuracy can be affected by hydrologic events. This also indicates the areaweighted flow method described in Section can successfully be used to compute accretions within acceptable ranges of gaging error. No adjustments are proposed to the area-weighed method results to compute the final accretions beyond the calculation described in Section Computation of Ungaged Accretions from Subbasins to the Yuba River above Englebright Dam As described in Section 3.1.5, using the area-weighted flow methodology, ungaged Yuba River accretions above Englebright Dam can be allocated to individual subbasins. Table shows the ungaged subbasins contributing to total ungaged Yuba River accretions above Englebright Dam. Oregon Creek above Log Cabin Dam is used as the index watershed for all subbasins. As computed for the ungaged North Yuba River accretions above New Bullards Bar Dam, ungaged Yuba River accretions above Englebright Dam from the individual subbasins are added Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

243 together and compared to the total Yuba River accretions above Englebright Dam to ensure all areas have been included Middle Yuba River (Middle Reach) Accretions Accretions were computed for the Middle Yuba River between Our House Dam and Oregon Creek using the methodology described above, comparing the area of the Middle Yuba River between Our House Dam and Oregon Creek with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to the Middle Yuba River between Our House Dam and Oregon Creek. Table Computed Monthly Average Accretions to the Middle Yuba River between Our House Dam and Oregon Creek. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Middle Yuba River (Middle Reach) Accretions 2 Notes: 1 Period of Record: 10/1/1969 through 9/30/ Middle Yuba River below Our House Dam accretions computed for the reach between Our House Dam and Oregon Creek using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Middle Yuba River (Lower Reach) Accretions Accretions were computed for the Middle Yuba River below Oregon Creek using the methodology described above, comparing the area of the Middle Yuba River below Oregon Creek with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to the Middle Yuba River below Oregon Creek. Table Computed Monthly Average Accretions to the Middle Yuba River below Oregon Creek. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Middle Yuba River (Lower Reach) Accretions 2 Notes: 1 Period of Record: 10/1/1969 through 9/30/ Middle Yuba River below Oregon Creek accretions computed for reach between Oregon Creek and the confluence of the Middle Yuba River and the North Yuba River using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Oregon Creek Accretions Accretions were computed for Oregon Creek below Log Cabin Dam using the methodology described above, comparing the area of Oregon Creek below Log Cabin Dam with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to Oregon Creek below Log Cabin Dam. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-39

244 Table Computed Monthly Average Accretions to the Oregon Creek below Log Cabin Dam. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Oregon Creek Accretions Notes: 1 Period of Record: 10/1/1969 through 9/30/ Oregon Creek below Log Cabin accretions computed for the reach between Log Cabin and the confluence of the Oregon Creek and the Middle Yuba River using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet South Yuba River Accretions Accretions were computed for the South Yuba River below Jones Bar using the methodology described above, comparing the area of the South Yuba River below Jones Bar with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to the South Yuba River below Jones Bar. Table Computed Monthly Average Accretions to the South Yuba River below Jones Bar. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) South Yuba River Accretions Notes: 1 Period of Record: 10/1/1969 through 9/30/ South Yuba River below Jones Bar accretions computed for Oregon Creek between Jones Bar and the confluence of the South Yuba River and the Yuba River using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Accretions to Englebright Reservoir Accretions were computed the subbasin contributing to inflows directly to Englebright Reservoir below the Middle Yuba River using the methodology described above, comparing the area of the subbasin contributing to Englebright Reservoir with the area and flow of Oregon Creek above Log Cabin Dam. Table shows the computed monthly average accretions to NBB. Table Computed Monthly Average Accretions Englebright Reservoir. Location Average 1 Monthly Accretions (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Accretions to Englebright Reservoir Notes: 1 Period of Record: 10/1/1969 through 9/30/ Englebright Reservoir accretions computed for the area between the Middle Yuba River and Englebright Dam using methodology described in Section Key: cfs=cubic feet per second TAF=thousand acre-feet Computation of Englebright Reservoir Evaporation Similar to NBB, Englebright Reservoir evaporation can play a substantial role in the hydrologic analysis of the watershed. Since Englebright Reservoir s water surface elevation does not have a Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

245 dramatic seasonal or monthly change, a constant water surface area of 810 acres is used for analysis. Monthly evaporation rates for Englebright Reservoir, published by DWR as part of the HEC-3 model of the Yuba River watershed, are shown in Table Table Computed Monthly Englebright Reservoir Evaporation Rates. Monthly Evaporation Rate (inches) Location Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Englebright Reservoir Source: From DWR HEC-3 Yuba River Watershed Model. January 1985 Applying the monthly evaporation rates to the constant reservoir surface area yields average monthly evaporation volumes, as shown in Table Table Computed Monthly Englebright Reservoir Evaporation Volumes. Location Monthly Evaporation (AF) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total Englebright Reservoir ,629 Notes: 1 Englebright Reservoir evaporation computed by multiplying reservoir evaporation rates from Table with reservoir surface area of 810 acres. Key: AF= acre-feet 3.3 Lower Yuba River Accretions This section describes accretions to the lower Yuba River. The Lower Yuba River is defined as the reach between Englebright Dam and the confluence of the Yuba River and the Feather River. Lower Yuba River accretions and depletions were calculated using the mass balance approach discussed in the NBB and Englebright Reservoir sections above. The positive ungaged flows calculated using this mass balance are considered to be accretions, and the negative ungaged flows as depletions. MRY accretions MRY DGP DC SM ) gage ( gage gage MRY accretions = lower Yuba River accretions; MRY gage = Marysville gage flows; DGP = Daguerre Point Dam diversions; DC gage = Deer Creek gage flows; and SM gage = Smartsville gage flows. where The Marysville, Deer Creek and Smartsville flows are from USGS gages , , and , respectively. Daguerre Point Dam diversions are from YCWA records of daily deliveries to YCWA s member units. While there are USGS gages on the three YCWA Daguerre Point Dam diversions (Hallwood-Cordua Canal, Pumpline Diversion and Brophy- Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-41

246 South Yuba Canal), the USGS gage period of record is less complete and shorter than YCWA s diversion records, so diversion records were used in this analysis instead. Accretions in the lower Yuba River watershed are dependent on several factors including the following: Precipitation; The Yuba Goldfields; Seepage losses; and Inflows from the Dry Creek watershed. While precipitation would be expected to have a noticeable effect, there is no clear correlation between precipitation and increased accretions. While Yuba River flows are typically higher immediately following precipitation events, this is most likely due to accumulated inflows from the upper basin. Within the lower basin, however, accretions do not generally reflect precipitation events. The Yuba Goldfields are an approximately 8-mile-long reach of the river, distinguished by large mounds of cobbled rock. The Yuba Goldfields have been subject to more than 100 years of dredging and the result is a reservoir, of sorts, with an estimated 500 TAF of storage. Based on anecdotal evidence, the Yuba Goldfields fill during high-flow periods, and discharge to the river during low-flow periods. While there is some correlation between flow at Smartsville and the amount of accretions or depletions in the lower Yuba River, the correlation is relatively weak and is not reliable for the observed range of conditions of the lower Yuba River. In addition, river depletions due to the Yuba Goldfields during high-flow periods are of less concern than would be if they occurred during low-flow periods, when flow contributions are more critical. Accretions and depletions in the lower Yuba River due to seepage losses are similarly difficult to quantify. While it is well known that there is interaction between the surface water and groundwater resources of Yuba County, no quantifiable relationship has yet been determined. While inflows from Dry Creek are discussed in Section 3.4, within the context of the computed lower Yuba River accretions described above, there is no clear relationship between gaged Dry Creek flows and the computed lower Yuba River accretions for the available POR. Despite application of several methods of analysis of lower Yuba River accretions, no reasonable results were achieved. As part of the analysis process, estimates of lower Yuba River accretion rates were compared to historic flow in the river and were generally found to be less than 5 percent of the river flow. Since the actual contribution to Yuba River flows from these accretions is minimal, the effect of these accretions on operations of the YRDP was examined. Releases from New Bullards Bar and Englebright reservoirs overwhelm computed accretions and depletions of the lower Yuba River. Accordingly, although project operations may include some minimal buffering for accretions and depletions in the lower Yuba River, the actual volume of Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

247 accretions and depletions is within the gage error and can thus be ignored in analysis of the basin. 3.4 Dry Creek Dry Creek flows near the western edge of Yuba County; its watershed is approximately 108 square miles, with its headwaters near the town of Challenge at elevation 3,155 feet msl. Flowing generally southward, Dry Creek flows are captured by Merle Collins Reservoir, a 57 TAF reservoir at approximately 1,160 feet msl formed by Virginia Ranch Dam. Merle Collins Reservoir is owned and operated by Browns Valley Irrigation District. Dry Creek is approximately 12 miles long from Virginia Ranch Dam to the confluence with the Yuba River. Dry Creek releases from Merle Collins Reservoir are augmented by accretions from local runoff and agricultural return flows, flowing into the Yuba River approximately 10 miles below Englebright Dam. Thirty-seven square miles of the Dry Creek watershed lie below Merle Collins Reservoir. Available flow records from 1964 through 1980 indicate Dry Creek flows to the Yuba River are about 55 TAF per year, with peak flows occurring from January through April and low flows occurring from June through October. Dry Creek flows below Merle Collins Reservoir were measured by USGS Gage , approximately 5 miles upstream from Dry Creek s confluence with the Yuba River, from August 1, 1964 through October 3, 1980, but since 1980, no flow records exist. As a result of this limited POR, it has been determined that Dry Creek flows to the Yuba River must be calculated by synthesis of data from a similar watershed. Several methods for deriving Dry Creek flows were examined, including the area-weighted flow methodology described in Section 3.1.3, an area-precipitation-based methodology, and a statistical correlation using existing gage data. The area-weighted flow methodology using the Oregon Creek watershed used for other subwatershed areas was attempted, but it was abandoned due to a lack of correlation with available data. Although the area-weighted flow methodology using the Oregon Creek watershed worked well in other parts of the Yuba River Basin, there are considerable differences in watershed characteristics between Oregon Creek and Dry Creek, invalidating a comparison between the two. The area-precipitation method, which was also examined, did not adequately characterize local runoff from Dry Creek due to the complex nature of its watershed at lower elevations. Historical records indicate year-around flow in Dry Creek, whereas the area-precipitation method only yields flow during precipitation events. Due to its watershed s similarity to Dry Creek s watershed, Deer Creek was selected as a representative watershed for Dry Creek; both watersheds are subject to multiple impairments, the impairments and watersheds have similar characteristics. Both receive runoff from elevations ranging from 140 feet msl to 1,208 feet msl, and both creeks receive considerable local runoff from agricultural or other non-precipitation-based sources. A comparison of data from the available POR of Dry Creek with the same POR of Deer Creek near Smartsville gage (USGS Gage ) indicates similar flow patterns. A correlation of all daily flows from the Deer Creek gage with flows from the Dry Creek gage yields a relationship indicating Dry Creek flows are approximately 68 percent of Deer Creek flows, and Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-43

248 developing monthly coefficients slightly improved the accuracy of the relationship. The resulting equation is the following: Table includes the monthly coefficients, A and B. From January through May, the Deer Creek coefficient dominates the relationship, corresponding to periods of rainfall runoff. From June through December, flows in Dry Creek are essentially the same from year to year, with little correlation to Deer Creek flows. During this period, Dry Creek flows are primarily composed of releases from Merle Collins Reservoir. Table Monthly Coefficients for Computing Dry Creek Flow from Deer Creek Gage Data. Coefficient Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A B Table shows the monthly average computed accretions from Dry Creek. Table Monthly Average Computed Dry Creek Accretions to the Yuba River. Average 2 Monthly Flow (cfs) Location Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Dry Creek Accretions Notes: 1 Dry Creek accretions to the Yuba River computed using methodology described in Section Period of record is 10/1/1969-9/30/2008 Key: cfs = cubic feet per second TAF = thousand acre-feet Total (TAF) 4.0 Unimpaired Flows As previously described, flows on the Yuba River are impaired by the YRDP, the SFFRP, the YB and the DS projects. Unimpaired flow would be the flow if neither those projects, nor any other artificial impoundments or diversions were present in the basin. This section describes the computation of unimpaired flows from the North, Middle, and South Yuba rivers and the total Yuba River flow at Smartsville. Timeseries for the unimpaired flows can be found in Attachment 2-2E, the Hydrology CD. 4.1 North Yuba River Determination of unimpaired flows from the North Yuba River is relatively straightforward due to the Goodyears Bar gage (USGS ), the two gages on Slate Creek and the Slate Creek Diversion (USGS and , respectively), and the computation of accretions as described in Section 3.1. Unimpaired North Yuba River flow at the New Bullards Bar Dam site is computed by adding Goodyears Bar gaged flow, Slate Creek and Slate Creek Diversion gaged flows, and accretions Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

249 from Canyon Creek, Slate Creek, the North Yuba River, and to the New Bullards Bar Reservoir area. Since the Middle and South Yuba rivers only have unimpaired data available for the period of 10/1/1975 through 9/30/2008, unimpaired North Yuba River flows are computed for a similar POR. Table shows the computed monthly average unimpaired Yuba River flow at the New Bullards Bar Dam site. Table Computed Monthly Average Unimpaired North Yuba River Flow at New Bullards Bar Dam. Location Average 9 Monthly Flow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) North Yuba River Inflow ,015 1,218 1,330 1, Slate Creek Inflow North Yuba River Accretions 3 Canyon Creek Accretions Slate Creek Accretions Accretions to New Bullards Bar Reservoir Slate Creek Diversion Total Inflow ,472 2,164 2,496 2,831 2,674 2,869 1, ,078 Notes: 1 North Yuba River at Goodyears Bar flow from USGS Gage Slate Creek flow from USGS Gage North Yuba River accretions between Goodyears Bar and the confluence of the North Yuba River and Slate Creek as described in Section Canyon Creek accretions as described in Section Slate Creek accretions between USGS Gage and the confluence of Slate Creek and the North Yuba River as described in Section North Yuba River accretions to the New Bullards Bar Reservoir area as described in Section Slate Creek Diversion flow from USGS Gage Total Inflow is the sum of gaged flows and accretions 9 Period of record is 10/1/1975-9/30/2008 Key: cfs = cubic feet per second TAF = thousand acre-feet USGS=U.S. Geological Survey 4.2 Middle Yuba River Unimpaired Middle Yuba River flow requires analysis of unimpaired Middle Yuba River flow from the upper watershed to the Milton Diversion Dam plus accretions between the Milton Diversion Dam and Our House Dam, shown in Figure Unimpaired Middle Yuba River flow at the Milton Diversion Dam was obtained through data prepared by NID for the Yuba-Bear Project FERC relicensing. The POR of data provided by NID for these flows is October 1, 1975 through September 30, Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-45

250 Source: MWH Americas, Inc. Figure Middle Yuba River Subbasin between Milton Diversion Dam and Our House Dam Middle Yuba River accretions between Milton Diversion Dam and Our House Dam were computed using gage data from below Milton Diversion Dam (USGS ) and the computed inflows to Our House Dam, as described in Section 2.3. Gage data at Milton Diversion Dam was only available for the POR of October 1, 1987 through September 30, Based on the POR collected, Middle Yuba River accretions between the Milton Diversion Dam and Our House Dam were determined for the full POR through the area-weighted flow approach described in Section 3.1.5, using Oregon Creek as a representative watershed. The watershed area between the Milton Diversion Dam and Our House Dam is square miles and has an average annual precipitation of 69 inches. When compared to Oregon Creek s watershed above Log Cabin Dam, the ratio of flow is The synthesized inflows compared very well with those computed using available gage data. Since there are no impairments to Oregon Creek upstream of Log Cabin Dam, Oregon Creek inflows to Log Cabin Dam can be considered unimpaired flows. Adding the unimpaired flow of the Middle Yuba River at Our House Dam, unimpaired Oregon Creek flow, calculated Middle Yuba River accretions below Our House Dam, and calculated Oregon Creek accretions below Log Cabin yields the unimpaired Middle Yuba River flow at its confluence with the North Yuba River. Table shows the monthly average unimpaired Middle Yuba River flow at its confluence with the North Yuba River. Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012

251 Table Monthly Average Unimpaired Middle Yuba River Flow at its Confluence with the North Yuba River. Location Average 8 Monthly Flow (cfs) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total (TAF) Middle Yuba River above Milton Diversion Dam 1 Middle Yuba River (Upper Reach) Accretions 2 Oregon Creek Inflow Middle Yuba River (Middle Reach) Accretions 4 Middle Yuba River (Lower Reach) Accretions 5 Oregon Creek Accretions Total Inflow ,181 1,228 1, Notes: 1 Unimpaired Middle Yuba River flow at Milton Diversion Dam from NID Yuba-Bear Project Relicensing 2 Middle Yuba River accretions between Milton Diversion Dam and Our House Dam computed using the methodology described in Section Oregon Creek flow above Log Cabin Dam from USGS Gages , , , and as described in Section Middle Yuba River accretions between Our House Dam and the confluence of the Middle Yuba River and Oregon Creek, as shown in Table Middle Yuba River accretions between the confluence of the Middle Yuba River and Oregon Creek and the confluence of the Middle Yuba River and the Yuba River, as described shown in Table Oregon Creek accretions between Log Cabin Dam and the confluence of the Middle Yuba River and Oregon Creek, as shown in Table Total inflow is the sum of gaged flows and accretions 8 Period of record is 10/1/1975-9/30/2008 Key: cfs = cubic feet per second TAF = thousand acre-feet USGS=U.S. Geological Survey 4.3 South Yuba River Historical unimpaired South Yuba River flow is computed by adding the unimpaired South Yuba River flow at Langs Crossing and Canyon Creek below Bowman Lake, as reported by PG&E in their FERC relicensing of the Drum-Spaulding Project, with South Yuba River and Canyon Creek accretions above Jones Bar. Unimpaired South Yuba River flow at Langs Crossing and Canyon Creek flow below Bowman Lake was provided for the period of October 1, 1975 through September 30, Accretions between the upstream locations and Jones Bar were computed using historical gage information from South Yuba River at Langs Crossing (USGS ), Canyon Creek below Bowman Reservoir (USGS ) and South Yuba River at Jones Bar ( ) for the full period of record. Figure shows the subbasin between Bowman Lake, Langs Crossing, and Jones Bar. Hydrology Report Technical Memorandum 2-2 Attachment 2-2D November , Yuba County Water Agency Page D-47

252 Source: MWH Americas, Inc. Figure South Yuba River Subbasin between Canyon Creek, Langs Crossing, and Jones Bar South Yuba River accretions below Jones Bar were computed using the process described in Section Table shows the monthly average unimpaired South Yuba River flow at its confluence with the Yuba River. Table Monthly Average Unimpaired South Yuba River Flow at its Confluence with the Yuba River. Location Average 4 Monthly Flow (cfs) Total Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (TAF) South Yuba River at Langs ,152 1, Crossing 1 Canyon Creek at Bowman Reservoir 2 South Yuba River (Upper) Accretions 3 South Yuba River (Lower) Accretions 3 Total Inflow ,159 1,394 1,727 2,080 2,601 1, Notes: 1 South Yuba River at Langs Crossing from PG&E Drum Spaulding FERC relicensing 2 Canyon Creek at Bowman Reservoir from PG&E Drum Spaulding FERC relicensing 3 Accretions on the South Yuba River between Jones Bar and the confluence of the South Yuba River and the Yuba River as shown in Table Total inflow is the sum of gaged flows and accretions 5 Period of record is 10/1/1975-9/30/2008 Key: YRDP = cfs = cubic feet per second TAF = thousand acre-feet Attachment 2-2D Technical Memorandum 2-2 Hydrology Report Page D , Yuba County Water Agency November 2012