Bucks Creek Hydroelectric Project FERC Project No. 619

Transcription

1 PACIFIC GAS AND ELECTRIC COMPANY Bucks Creek Hydroelectric Project FERC Project No. 619 DRAFT Data for Study Plans WR-S3 and WR-S4 October 2015

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3 PACIFIC GAS AND ELECTRIC COMPANY AND THE CITY OF SANTA CLARA Bucks Creek Hydroelectric Project FERC Project No. 619 DRAFT Data for Study Plans WR-S3 and WR-S4 October 2015

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5 Bucks Creek Hydroelectric Project FERC Project No. 619 Data for Study Plans WR-S3 and WR-S4 TABLE OF CONTENTS SECTION 1.0 INTRODUCTION SECTION 2.0 HEC-RESSIM INPUT Unimpaired to Bucks Lake Unimpaired to Lower Bucks Lake Unimpaired Accretion to Bucks Creek At North Fork Feather River (NFFR) Unimpaired to Grizzly Forebay Unimpaired Accretion to Grizzly Creek At NFFR Unimpaired to Three Lakes Unimpaired to Diversions 1-9 of Milk Ranch Conduit Unimpaired Accretion to Milk Ranch Creek at NFFR SECTION 3.0 IHA DSS DATASETS Regulated Bucks Creek at NFFR Unimpaired Bucks Creek at NFFR Regulated Grizzly Creek at NFFR Unimpaired Grizzly Creek at NFFR Regulated Milk Ranch Creek at NFFR Unimpaired Milk Ranch Creek At NFFR APPENDICES Appendix A Appendix B Unimpaired Development for Bucks and Grizzly Creeks Bucks System Fact Sheet October 2015 Page i Table of Contents

6 LIST OF TABLES Table HEC-ResSim Input DSS Records Table IHA Dataset DSS Records Table Observed Gage DSS Records Table Contributing Area and Area Factor for the Milk Ranch Conduit Watersheds Table of Contents Page ii October 2015

7 LIST OF FIGURES Figure Bucks Creek Hydroelectric Project Facilities Figure Stream and Stage Gages in the Project Area Figure Watershed Boundaries Used in the IHA and ResSim Analyses Figure Upper Bucks Creek Watershed Area Figure Bucks Lake Subwatershed Area Figure Lower Bucks Lake Watershed Area Figure Lower Bucks Creek Watershed Area (Minus the Watershed Areas for Diversions 6-9) Figure Upper Grizzly Creek Watershed Area Figure Lower Grizzly Creek Watershed Area Figure Three Lakes Watershed Area Figure Watershed Areas for Milk Ranch Conduit Diversions Figure Lower Milk Ranch Creek Watershed Area Figure Watershed Area of Total Bucks Creek Unimpaired s at NFFR Figure Watershed Area of Total Grizzly Creek Unimpaired s at NFFR Figure Watershed Area of Total Milk Ranch Creek UIF at NFFR October 2015 Page iii Table of Contents

8 This Page Intentionally Left Blank Table of Contents Page iv October 2015

9 SECTION 1.0 Introduction There are two study plans in the Bucks Relicensing Project that address stream flow. Study Plan WR-S3 is tasked with completing an Indicators of Hydrologic Alterations (IHA) analysis for the project reaches, while Study Plan WR-S4 is tasked with developing a computerized water balance model using the Army Corps of Engineers model HEC-ResSim (ResSim) to simulate current and potential future changes in project operations. The purpose of this document is to describe the assumptions, methods, and calculations used to develop the data used in the IHA analysis and for the ResSim operations model. Figure Bucks Creek Hydroelectric Project Facilities. The Project is in the North Fork Feather River drainage basin. There are three watersheds within the basin which include Bucks Creek, Grizzly Creek, and Milk Ranch Creek (Figure 1.0-1). These watersheds originate near the crest of the northern Sierra Nevada Mountains at elevations up to 7,000 feet. Bucks Creek flows approximately 15 miles through Bucks Lake and Lower Bucks Lake October 2015 Page 1-1 Introduction

10 before joining the North Fork Feather River. The Bucks Creek basin can be divided into upper and lower portions, with the split located at Lower Bucks Diversion Dam. Grizzly Creek flows approximately 16 miles from its headwaters region just south of Bucks Lake through Grizzly Forebay and into the North Fork Feather River. Upper Grizzly Creek includes the area that drains into Grizzly Forebay, and Lower Grizzly Creek begins at the Grizzly Forebay Dam. Milk Ranch Creek flows approximately 4 miles from the Three Lakes Reservoir area to the North Fork Feather River. It is located to the north of the other drainages in the Project and has the smallest drainage area. Project reservoirs include the Bucks Lake and Lower Bucks Lake impoundments on Bucks Creek, Grizzly Forebay impoundment on Grizzly Creek, and Three Lakes Reservoir impoundment on Milk Ranch Creek. from Bucks Lake is released and immediately flows into Lower Bucks Lake. The Milk Ranch Conduit conveys flow from Three Lakes Reservoir and small intervening tributary diversions to Lower Bucks Lake. Water from Lower Bucks Lake travels through the Grizzly Powerhouse Tunnel to Grizzly Powerhouse and discharges into Grizzly Forebay. Instream flow releases are made from Lower Bucks Lake into Bucks Creek. Water from Grizzly Forebay travels through the Grizzly Forebay Tunnel to the Bucks Creek Powerhouse and discharges into the Rock Creek Reach of the North Fork Feather River upstream of Cresta Reservoir. Instream flow releases are made from Grizzly Forebay into Grizzly Creek. The IHA program requires time series of unimpaired flow and regulated flow that are then compared to describe the effects of flow regulation on the creek. The ResSim analysis requires unimpaired flow as input to the reservoirs and accretions to the lower watersheds. These flow time-series are manipulated by the model under an assumed set of Project operations. The data for the IHA and ResSim are accessed through the U.S. Army Corps of Engineers program DSS. The DSS interface is shown in Table and Table These tables also provide a direct link in this report to the description of the development of these data. Selecting the name (Part B) of the DSS dataset will direct the user to the section in this report that describes the assumptions, methods, and calculations used to develop that dataset. Additionally, each section heading in this document is the same as the name (Part B) of datasets in the DSS files, with the purpose of providing a way to easily navigate through a hard copy of this document. Furthermore, the last column in each table (Equation Variables) is included to help the user understand which equation variables correspond to which DSS path names (Part B). Section 1.0 Page 1-2 October 2015

11 Table HEC-ResSim Input DSS Records Part A: Group Name Part B: Location Part C: Parameter (Unit) Part D: Date Range Part E: Time-Step Part F: Record Type Additional Description Bucks Creek Unimpaired Bucks Creek At NFFR Accretion (cfs) 01jan jan2013 1day Calc_Prorated Grizzly Eqn_ Does not Include Div6-9 UIF Bucks Creek Unimpaired s From Lower Bucks Watershed Only 01jan jan2013 1day Calc_Prorated Bucks Eqn Bucks Creek Unimpaired s From Upper Bucks Watershed Only 01jan jan2013 1day Calc Smooth_Bucks Mass Balance Eqn Grizzly Creek Unimpaired Grizzly Creek At Grizzly Forebay 01jan jan2013 1day Calc Smooth_Grizzly Mass Balance Eqn Grizzly Creek Unimpaired Grizzly Creek At NFFR Accretion 01jan jan2013 1day Calc_Prorated Grizzly Eqn Milk Ranch Conduit Div1 Out Dummy 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 1 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 2 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 3 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 3 Decommissioned 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 3 In Use 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 4 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 5 01jan jan2013 1day Calc_Prorated Bucks Eqn October 2015 Page 1-3 Introduction

12 Part A: Group Name Part B: Location Part C: Parameter (Unit) Part D: Date Range Part E: Time-Step Part F: Record Type Additional Description Milk Ranch Conduit Diversion 6 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 7 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 8 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Conduit Diversion 9 01jan jan2013 1day Calc_Prorated Bucks Eqn Milk Ranch Creek Unimpaired Milk Ranch Creek At NFFR Accretion 01jan jan2013 1day Calc_Prorated Grizzly Eqn_ Does Not Include Div1-5 Uifs Milk Ranch Creek Unimpaired Milk Ranch Creek At Three Lakes 01jan jan2013 1day Calc_Prorated Bucks Eqn Section 1.0 Page 1-4 October 2015

13 Table IHA Dataset DSS Records Part A: Group Name Part B: Location Part C: Parameter (Unit) Part D: Date Range Part E: Time-Step Part F: Record Type_Additional Description Bucks Creek Regulated Bucks Creek At North Fork Feather River 01JAN JAN2013 1day Calc_Regulated s Bucks Creek Unimpaired Bucks Creek At North Fork Feather River 01JAN JAN2014 1day Calc_Bucks Eqn+Prorated Grizzly Eqn Grizzly Creek Regulated Grizzly Creek At North Fork Feather River 01JAN JAN2015 1day Calc_Regulated s Grizzly Creek Unimpaired Grizzly Creek At North Fork Feather River 01JAN JAN2016 1day Calc_Grizzly Eqn+Prorated Grizzly Eqn Milk Ranch Creek Regulated Milk Ranch Creek At North Fork Feather River 01JAN JAN2017 1day Calc_Regulated s Milk Ranch Creek Unimpaired Milk Ranch Creek At North Fork Feather River 01JAN JAN2018 1day Calc_Prorated Bucks Eqn+Prorated Grizzly Eqn October 2015 Page 1-5 Introduction

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15 Available data measurements of regulated flows, i.e. those flows influenced by Project operations are available from both U.S. Geological Survey (USGS) and PG&E for various locations in the Project. Currently, there are no measurements of unimpaired flows (flows not influenced by Project operations) upstream of Project facilities. Because of this, unimpaired flows need to be estimated through mass-balance analysis using the measured flows. The mass-balance approach as applied to the Project has been reviewed and approved by the Technical Working Group for the Project s Studies WR-S3 and WR-S4. The streamflow, storage, and precipitation gages in the Project area used for the IHA and ResSim analyses are listed in Table 2-1. The location of the streamflow gages in the Project Area, is shown in Figure The watershed boundaries and naming convention for the watersheds is shown in Figure October 2015 Page 1-1 Section 2.0

16 Table Observed Gage DSS Records Part A: Group Name Part B: Location Part C: Parameter (Unit) Part D: Date Range Part E: Time-Step Part F: Record Type_Additional Description Bucks Creek Bucks Creek At Lower Bucks Lake (cfs) 01JUN JAN2013 Daily Gage: USGS _ PG&E NF12+NF82 Bucks Creek Bucks Creek At North Fork Feather River 01JAN JAN2013 Daily Gage: PG&E-Bucks1 Bucks System Infrastructure Bucks Powerhouse 01JAN JAN2013 Daily Gage: USGS _ PG&E -NF20 Bucks System Infrastructure Bucks Tunnel Inlet-Outlet 01JAN JAN1994 Daily Gage: USGS (Out)_USGS _ PG&E NF-40(In) Bucks System Infrastructure Grizzly Powerhouse 01JAN JAN2013 Daily Gage: USGS _ PG&E -NF108 Bucks System Infrastructure Milk Ranch Conduit Outfall 01JAN JAN2013 Daily Gage: USGS _ PG&E -NF11 Bucks System Reservoirs Grizzly Forebay Storage (Ac-Ft) At JAN JAN2013 Daily Gage: USGS _ PG&E -NF19 Bucks System Reservoirs Lower Bucks Lake Storage (Ac-Ft) At JAN JAN2013 Daily Gage: USGS _ PG&E -NF13 Bucks System Reservoirs Bucks Lake Storage (Ac-Ft) At JAN JAN2013 Daily Gage: USGS _ PG&E -NF16 Grizzly Creek Grizzly Creek At Grizzly Forebay 01JUN JAN2013 Daily Gage: USGS _ PG&E -NF22 Grizzly Creek Grizzly Creek At North Fork Feather River 01JAN JAN2013 Daily Gage: Pge-GR1 Milk Ranch Creek Milk Ranch Creek At North Fork Feather River 01JUN JAN2013 Daily Gage: Pge-MR1 North Fork Feather River North Fork Feather River At Grizzly Creek 01JAN JAN2013 Daily Gage: USGS Section 2.0 Page 1-2 October 2015

17 Part A: Group Name North Fork Feather River Part B: Location North Fork Feather River At Rock Forebay Part C: Parameter (Unit) References Bucks Station Rain Gage Depth References Bucks Creek Powerhouse Station Rain Gage Depth References Bucks Station Snow Gage Depth References Canyon Dam Station Rain Gage Depth References Quincy Station Rain Gage Depth References Spanish Creek At Keddie Gage Bucks Creek Cks Creek Bucks Creek At Lower Bucks Lake Bucks Creek At North Fork Feather River Part D: Date Range 01JAN JAN JAN JAN JAN JAN JAN JAN JAN JAN JAN JAN JAN JAN JUN JAN JAN JAN2013 Part E: Time-Step Daily Daily Daily Daily Daily Daily Part F: Record Type_Additional Description Gage: USGS _ PG&E -NF57 Ghcnd:Usc Gage: Bup Ghcnd:Usc Ghcnd:Usc Ghcnd:Usc Daily Gage: USGS Daily Daily Gage: USGS _ PG&E NF12+NF82 Gage: PG&E -Bucks1 October 2015 Page 1-3 Section 2.0

18 Figure Stream and Stage Gages in the Project Area. Section 2.0 Page 1-4 October 2015

19 Figure Watershed Boundaries Used in the IHA and ResSim Analyses. October 2015 Page 1-5 Section 2.0

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21 SECTION 2.0 HEC-ResSim Input 2.1 Unimpaired to Bucks Lake Bucks Lake and Lower Bucks Lake are subwatersheds of the Upper Bucks Creek Watershed (Figure 1.0-3). The unimpaired flow (UIF) to Bucks Lake is derived from a single time series of the Upper Bucks Creek Watershed UIF, a synthesized flow that is calculated from a mass-balance analysis of the storage and releases from the reservoirs. The UIF for Upper Bucks Creek Watershed is calculated using the following equation: UIFUBC= Δ NF13 + Δ NF16 - NF11 + NF12 + NF82 + NF40 + NF108 Eqn Where: UIFUBC Δ NF13 Δ NF16 NF11 NF12 NF82 NF40 NF108 = UIF for Upper Bucks Creek Watershed = 24hr Change Lower Bucks Lake storage (measured). = 24hr Change Bucks Lake storage (measured). = at the outlet of Milk Ranch Canal (measured). = at Bucks Diversion Dam Spill (measured). = in Bucks Creek below Bucks Diversion Dam (measured). = in Bucks Creek Tunnel Outlet near Storrie (measured). = in Grizzly Powerhouse (measured). The two reservoirs in the Upper Bucks Creek Watershed are operated separately in ResSim and therefore the model needs inflow to each reservoir. The UIF to each reservoir was estimated from the Upper Bucks Creek Watershed UIF (equation 3.1-1). The disaggregation of the two lake inflows from the total watershed flow was accomplished by multiplying the Upper Bucks Creek Watershed UIF by the prorated area of each sub-watershed. October 2015 Page 2-1 Section 3.0 Bucks Creek Project, FERC Project No. 619

22 The UIF for Bucks Lake only is calculated using the following equation: UIFBL= AF * UIFUBC Eqn Where: UIFBL = UIF for Bucks Lake UIFUBC = UIF for Upper Bucks Creek Watershed (calculated, see Section 3.1, equation 3.1-1). AF = Area factor = Area of Bucks Lake subwatershed / Area of Upper Bucks Creek Watershed. = 28.7 acres / 31.1 acres = 0.92 See section 3.2 for the Lower Bucks Lake UIF calculation. Figure Upper Bucks Creek Watershed Area Section 3.0 Page 2-2 October 2015

23 Figure Bucks Lake Subwatershed Area October 2015 Page 2-3 Section 3.0 Bucks Creek Project, FERC Project No. 619

24 2.2 Unimpaired to Lower Bucks Lake The two Bucks Creek Watershed reservoirs are operated separately in ResSim and therefore the model needs inflow to each reservoir. The UIF to each reservoir was estimated from the Upper Bucks Creek Watershed UIF. The disaggregation of the two lake inflows from the total watershed flow was accomplished by multiplying the watershed UIF by the prorated area of each subwatershed. The UIF for Lower Bucks Lake only is calculated using the following equation: UIFLBL = AF * UIFUBC Eqn Where: UIFLBL = UIF for Lower Bucks Lake UIFUBC = UIF for Upper Bucks Creek Watershed (calculated, see Section 3.1, equation 3.1-1). AF = Area factor = Area of Lower Bucks Lake subwatershed / Area of Upper Bucks Creek Watershed. = 2.5 acres / 31.1 acres = 0.08 Section 3.0 Page 2-4 October 2015

25 Figure Lower Bucks Lake Watershed Area October 2015 Page 2-5 Section 3.0 Bucks Creek Project, FERC Project No. 619

26 2.3 Unimpaired Accretion to Bucks Creek At North Fork Feather River (NFFR) The operations model uses the UIF to the reservoirs to drive the reservoir operations and produce a reservoir outflow. The outflow from the reservoirs to the creek is then modified by the accretions to the creek. These accretions are considered to be unimpaired and are calculated using prorated areas of the upper watershed unimpaired flows. The Lower Bucks Creek Watershed is more similar in watershed characteristics to the Upper Grizzly watershed, than it is to the Upper Bucks Watershed. As a result, the unimpaired flows generated in the Lower Bucks Creek Watershed area are calculated to be proportional to the unimpaired flows generated in the Upper Grizzly watershed. The unimpaired flows generated in the Lower Bucks Creek Watershed (or the accretions to Bucks Creek) are calculated using the following equation: ACCBC = AF * UIFUGC Eqn Where: ACCBC = Accretions to Bucks Creek below Lower Bucks Lake (Lower Bucks Creek Watershed). UIFUGC = UIF for Upper Grizzly Creek Watershed (calculated, see Section 3.4, equation 3.4-1) AF = Area Factor = Area of Lower Bucks Creek Watershed / Area of Upper Grizzly Watershed = 12.7 acres / 14.6 acres = Areas from McGurk (2003) Section 3.0 Page 2-6 October 2015

27 Figure Lower Bucks Creek Watershed Area (Minus the Watershed Areas for Diversions 6-9) October 2015 Page 2-7 Section 3.0 Bucks Creek Project, FERC Project No. 619

28 2.4 Unimpaired to Grizzly Forebay The UIF of Grizzly Creek at Grizzly Forebay represents the natural flow conditions in the creek without the upstream hydroelectric facilities. This record is not measured but rather a synthesized value based on mass-balance using measured values. This UIF generated in the Upper Grizzly Creek watershed is estimated with the following massbalance equation: UIFUGC = NF19 + NF20 + NF22 NF40 NF108 Eqn Where: UIFUGC = synthesized unimpaired flow of Upper Grizzly Creek Watershed NF19 = 24hr change in Grizzly Forebay storage (measured). NF20 = Bucks Powerhouse flow (measured). NF22 = Grizzly Creek flow below dam (measured). NF40 = Bucks Tunnel Outlet flow (measured, not operational after 1993). NF108 = Grizzly Powerhouse flow (measured). Section 3.0 Page 2-8 October 2015

29 Figure Upper Grizzly Creek Watershed Area October 2015 Page 2-9 Section 3.0 Bucks Creek Project, FERC Project No. 619

30 2.5 Unimpaired Accretion to Grizzly Creek At NFFR The operations model uses the UIF to the reservoirs to drive the reservoir operations and generate a reservoir outflow. The modelled outflow from the reservoirs to each creek is then modified by the accretions to the creek. These accretions are considered to be unimpaired and are calculated using prorated areas of the upper watershed unimpaired flows. The unimpaired flows generated in the Lower Grizzly Creek Watershed (or the accretions to Grizzly Creek) are calculated using the following equation: ACCGC=AF * UIFUGC Eqn Where: ACCGC = Accretions to Grizzly Creek from Grizzly Forebay to NFFR UIFUGC = UIF for Upper Grizzly Creek Watershed (calculated, see Section 3.4, equation 3.4-1) AF = Area factor = Area of Lower Grizzly Creek Watershed / Area of Upper Grizzly Creek Watershed = 17.7 acres / 14.6 acres = 1.21 Section 3.0 Page 2-10 October 2015

31 Figure Lower Grizzly Creek Watershed Area October 2015 Page 2-11 Section 3.0 Bucks Creek Project, FERC Project No. 619

32 2.6 Unimpaired to Three Lakes The operations model uses the UIF for Milk Ranch Creek into Three lakes to drive that reservoir. In the model, the water is stored and released from the reservoir to Milk Ranch Creek based on PG&E operations. The synthesized UIF is based on the Upper Bucks Creek Watershed UIF and is prorated based on the areas of the Three Lakes watershed and the Upper Bucks Creek Watershed. UIFUMC = AF * UIFUBC Eqn Where: UIFUMC = UIF to Three Lakes UIFUBC = UIF for Upper Bucks Creek (calculated, See Section 3.1, equation 3.1-1) AF = Area factor = Area of Three Lakes Watershed / Area of Upper Bucks Creek Watershed. = 1.1 acres / 31.1 acres = Section 3.0 Page 2-12 October 2015

33 Figure Three Lakes Watershed Area October 2015 Page 2-13 Section 3.0 Bucks Creek Project, FERC Project No. 619

34 2.7 Unimpaired to Diversions 1-9 of Milk Ranch Conduit The operations model uses the UIF to the reservoirs and creeks to drive the reservoir simulations. There are 9 watersheds that are connected with the Milk Ranch Conduit (MRC). The flow in each watershed is a function of the Upper Bucks Creek Watershed UIF that has been prorated based on the areas of each of the contributing watersheds relative to the Upper Bucks Creek Watershed. For each watershed the equation for UIF is: UIFDIV1 = UIFUBC * AF Eqn Where: UIFDIVx = UIF to watershed x. UIFUBC = Upper Bucks Creek UIF (see equation 3.1-1) AF = Area factor = Area of a MRC diversion watershed / Area of Upper Bucks Creek Watershed. Table 2-1 lists the areas of each MRC diversion watershed and the area factor used in calculating the UIF. Table Contributing Area and Area Factor for the Milk Ranch Conduit Watersheds. Three Lakes Diversion Area (mi 2 ) Area Factor Notes: Area of Upper Bucks Creek Watershed is 31.1 mi 2 Diversion 1 is the area between the MRC and Three Lakes Dam. The first MRC diversion picks up both Diversion 1 watershed and the flow released to Milk Ranch Creek from Three Lakes. Diversion 3 has not been in operation since the flood of January Area Factors have been rounded for inclusion in the table. Section 3.0 Page 2-14 October 2015

35 Figure Watershed Areas for Milk Ranch Conduit Diversions 1-9 October 2015 Page 2-15 Section 3.0 Bucks Creek Project, FERC Project No. 619

36 2.8 Unimpaired Accretion to Milk Ranch Creek at NFFR The operations model uses the UIF to the reservoirs and creeks to drive the reservoir simulations. For Milk Ranch Creek, the accretion for the lower watershed is calculated based on the Lower Bucks Accretion and is prorated based on the areas of the lower watersheds of Bucks and Milk Ranch creeks. The equation for the Milk Ranch Creek accretion is: ACCLMC = AF * ACCLBC Eqn Where: ACCLMC ACCLBC AF = Accretions to Lower Milk Ranch Creek. = Accretions to Bucks Creek below Lower Bucks Lake (calculated, See Section 3.3, equation 3.3-1). = Area factor = Area of Lower Milk Ranch Creek 2 / Area of Lower Bucks Creek. = 4.9 acres / 14.5 acres = Area below the Milk Ranch Conduit Section 3.0 Page 2-16 October 2015

37 Figure Lower Milk Ranch Creek Watershed Area Section 3.0 Page 2-2 October 2015

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39 SECTION 3.0 IHA DSS Datasets 3.1 Regulated Bucks Creek at NFFR The regulated flow of Bucks Creek at the NFFR is the current flow conditions in the creek with the upstream hydroelectric facilities operating. Historically this flow is unmonitored but recently there has been a temporary streamflow gage in Bucks Creek immediately upstream of the NFFR. This gage only operates from June to October and been in service since The gage is only accurate at low flows (<100 cfs). Because the measured record is incomplete, a simulated record must be used to replicate long-term flows of Bucks Creek at NFFR. The regulated flow can be simulated from a combination of measured and calculated flows using the following equation: REGBC = NF82 + NF12 + AF * UIFUGC Eqn Where: REGBC NF12 NF82 UIFUGC AF = the regulated flow of Bucks Creek at the NFFR. = Bucks Diversion Dam Spill (measured). = Bucks Creek below Bucks Diversion Dam (measured). = the unimpaired flow of Upper Grizzly Creek Watershed (calculated, see Section 3.3, equation 3.3-1). = Area factor = Area of Lower Bucks Creek Watershed / Area of Upper Grizzly Creek Watershed = 12.7 acres / 14.6 acres = October 2015 Page 3-1 Section 4.0 Bucks Creek Project, FERC Project No. 619

40 3.2 Unimpaired Bucks Creek at NFFR The UIF of Bucks Creek at the NFFR is a simulated term based on a mass-balance analysis of the measured flow and storage in the Grizzly Creek and Bucks Creek systems (PG&E 2003, PG&E 2015). After analyzing the UIF for the upstream Grizzly and Bucks watersheds, it was determined that the conditions in the Lower Bucks Creek Watershed reflect conditions in the Upper Grizzly Watershed and the Upper Bucks Creek Watershed, and the UIF is a function of both. The UIF for Bucks Creek at the NFFR is calculated using the following equation: UIFBC = UIFUBC + ACCBC Eqn Where: UIFBC = Bucks Creek UIF at NFFR UIFUBC = Upper Bucks Creek Watershed UIF (calculated, see Section 3.1, equation 3.1-1) ACCBC = Accretions to Bucks Creek (calculated, see Section 3.3, equation 3.3-1) Figure Watershed Area of Total Bucks Creek Unimpaired s at NFFR Section 4.0 Page 3-2 October 2015

41 3.3 Regulated Grizzly Creek at NFFR The regulated flow of Grizzly Creek at the NFFR is the current flow conditions in the creek with the upstream hydroelectric facilities operating. Historically this flow is unmonitored; however, there is a temporary streamflow gage in Grizzly Creek immediately upstream of the NFFR. This gage only operates from June to October and has been in service since The gage is only accurate at low flows (<100 cfs). Because the measured record is incomplete, a simulated record must be used to replicate long-term flows of Grizzly Creek at NFFR. The regulated flow can be simulated from a combination of measured and calculated flows. The regulated flow for Grizzly Creek at the NFFR is calculated using the following equation: REGGC = NF22 + ACCGC Eqn Where: REGGC = the regulated flow of Lower Grizzly Creek. NF22 = Bucks Diversion Dam Spill (measured). ACCGC = Accretions to Grizzly Creek (calculated, see Section 3.5, equation 3.5-1) October 2015 Page 3-3 Section 4.0 Bucks Creek Project, FERC Project No. 619

42 3.4 Unimpaired Grizzly Creek at NFFR The UIF of Grizzly Creek at the NFFR is a simulated term based on a mass-balance analysis of the measured flow and storage in the Grizzly Creek and Bucks Creek systems (PG&E 2003, PG&E 2015). The flow in the lower river was estimated to be a function of the UIF in the upper river based on a proration of the watershed areas. The UIF for Grizzly Creek at the NFFR is calculated using the following equation: UIFGC = UIFUGC + ACCGC Eqn Where: UIFGC = Grizzly Creek UIF at NFFR UIFUGC = UIF for Upper Grizzly Creek Watershed (calculated, see Section 3.4, equation 3.4-1) ACCGC = Accretions to Grizzly Creek from Grizzly Forebay to NFFR (calculated, see Section 3.5, equation 3.5-1) Figure Watershed Area of Total Grizzly Creek Unimpaired s at NFFR Section 4.0 Page 3-4 October 2015

43 3.5 Regulated Milk Ranch Creek at NFFR The regulated flow of Milk Ranch Creek at the NFFR is the current flow conditions in the creek with the upstream hydroelectric facilities and the Milk Ranch Conduit operating. Historically this flow is unmonitored; however, there is a temporary streamflow gage in Milk Ranch Creek immediately upstream of the NFFR. This gage only operates from June to October and been in service since The gage is only accurate at low flows (<100 cfs). Because the measured record is incomplete, a simulated record must be used to replicate long-term flows of Milk Ranch Creek at NFFR. The regulated flow is estimated through operation of the ResSim program that simulates the operation of the Bucks Creek Hydroelectric System. The results of the model represent the regulated flow at the NFFR. This simulation will be performed after the ResSim baseline model has been accepted by the resource agencies. The model will be run with the UIF inputs described above and the baseline reservoir operations specified in the model. The results will be incorporated into the final draft of this report. October 2015 Page 3-5 Section 4.0 Bucks Creek Project, FERC Project No. 619

44 3.6 Unimpaired Milk Ranch Creek At NFFR The unimpaired flow UIF of Milk Ranch Creek at the NFFR is a synthesized term based on the unimpaired flow of Lower Bucks Creek Watershed. The UIF of Bucks Creek at NFFR is described in Section 3.3 with equation The UIF for Milk Ranch Creek at the NFFR is calculated using the following equation: UIFMRC = UIFUBC + ACCMRC Eqn Where: UIFMRC = UIF for Lower Milk Ranch Creek UIFUBC = UIF for Upper Bucks Creek Watershed (Calculated, see Section 3.1, equation 3.1-1) ACCMRC = Accretions to Lower Milk Ranch Creek (Calculated, see Section 3.8, equation 3.8-1) Figure Watershed Area of Total Milk Ranch Creek UIF at NFFR Section 4.0 Page 3-6 October 2015

45 Appendix A UNIMPAIRED FLOW DEVELOPMENT FOR BUCKS AND GRIZZLY CREEKS October 2015 Appendix A

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47 Introduction Synthesizing Unimpaired - Bucks and Grizzly Creeks BJ McGurk, McGurk Hydrologic 11 June 2015 The Bucks Creek Hydroelectric Project (Project) (FERC 619) license was modified in 2003 to accommodate revised recreation and flow conditions. As part of that process, unimpaired flow records were developed for the period from water year (WY) , for two of the three major streams in the system, namely Bucks Creek and Grizzly Creek (Figure 1). A mass balance technique was implemented that used daily flow records for inflows and outflows from various facilities on both streams. As part of the process the compiled daily flow data was smoothed to dampen fluctuations associated largely with measurement of lake levels. This smoothing resulted in synthesized flow record for both creeks that represents the natural outflow in both the upper and lower watersheds. The records can be used to assess hydrologic alterations to the project streams by comparing pre- and post-project flows using the Indicators of Hydrologic Alteration (IHA) procedure (The Nature Conservancy, 1997). October 2015 Page A-1 Appendix A

48 Figure 1. Map of Bucks Project subbasins, streams, and stream gages, and reservoir gages Additional license article modifications associated with application for a new FERC license were initiated in As part of the process, the relicensing Technical Working Group was tasked to update the unimpaired flow record for the Project by including recent flows in Grizzly Creek and Bucks Creek (i.e., ), and flows associated with Milk Ranch Creek ( ). This report describes the procedure used to develop the mass balance-based daily record, and the subsequent smoothing process, for the period between 1970 and 2001 for Bucks Creek and Grizzly Creek. Portions of the 2003 PG&E report (Indicators of Hydrologic Alteration, Bucks Creek Project, by BJ McGurk, 31 January 2003) are included below where appropriate. This report also describes modifications made to the data smoothing procedure for the period between 2001 and Mass Balance Procedure to Determine Unimpaired Appendix A Page A-2 October 2015

49 In the 2003 IHA report, the daily streamflows were synthesized using mass balance and area scaling techniques at four points within the Project Area. These points are: Bucks Creek at the Lower Bucks Lake Diversion Dam (referred to as Upper Bucks Creek Watershed); Bucks Creek at the North Fork Feather River (Lower Bucks Creek Watershed); Grizzly Creek at the Grizzly Forebay Dam (Upper Grizzly Watershed); and Grizzly Creek at the North Fork Feather River (Lower Grizzly Watershed). The Upper Bucks and Upper Grizzly flow points reflect flows generated upstream of the reservoirs. The Lower Bucks and Lower Grizzly flow points represent flow in each creek generated from the entire watershed. The mass balance procedure takes into account daily streamflow through powerhouses, reach inflow, changes in storage in reservoirs, forebays, and afterbays, and other known inflows such as conduits and outflows such as spills, tunnels, and minimum streamflow releases. The sum of streamflows and storage changes for each day produces a mass balance-based streamflow record for the two diversion points in the Project that approximates the streamflow that would occur at that point if no Project facilities were in place. The change in storage term includes several inflows and outflows that are not explicitly measured by the various gages used in the analysis. These terms include evaporation from and direct precipitation to the lakes, seepage, measurement error, and intermittent unmeasured flows. Stream gages used in the analysis and their PG&E number are shown in Table 1. Table 1. Stream, canal, conduit, and reservoir gaging stations in the Project Area Project ID USGS Number Period of Record Collection Type NF Manual Three Lakes Name NF Continuous Milk Ranch Canal at Outlet NF Continuous Bucks Diversion Dam Spill NF Continuous Lower Bucks Lake near Bucks Lodge NF Continuous Bucks Lake Near Bucks Lodge NF Continuous Grizzly (Forebay) Ck. Diversion Nr Storrie NF Calculated Bucks Creek Powerhouse NF Continuous Bucks Creek Tunnel Outlet near Storrie NF Continuous Grizzly Creek Below Grizzly Diversion Dam October 2015 Page A-3 Appendix A

50 Project ID USGS Number Period of Record Collection Type Name NF Continuous Bucks Creek Below Bucks Diversion Dam NF Calculated Grizzly Powerhouse The following mass balance equations were used to develop mean daily streamflow for the two diversion points, Upper Bucks and Upper Grizzly: Upper Bucks = Δ NF13 + Δ NF16 - NF11 + NF12 +NF82 + NF40 +NF108 (1) Upper Grizzly = Δ NF19 + NF20 + NF22 NF40 NF108 (2) (2) The term Δ indicates the daily difference between the midnight storage of the reservoir, and the value can be positive or negative. For Upper Bucks, the sum of the daily storage changes in Bucks Lake and Lower Bucks Lake, when combined with releases from the dam, removal of the Milk Ranch Conduit inflow, and drafts through the NF40 Tunnel or through Grizzly Powerhouse (NF108), represent the mean daily flow. For Upper Grizzly, the daily storage change in Grizzly Forebay, when combined with releases from the dam and drafts through Bucks Powerhouse, and with the removal of inflow from the NF40 Tunnel and draft for Grizzly Powerhouse, represent the mean daily flow. Evaporation Upper Bucks Lake, the largest reservoir in the system, is the dominant feature influencing evaporation. Based on its 1800 acres of surface area and measurements from an evaporation pan at nearby Lake Almanor, July and August evaporation can reach 9 inches of water loss per month. In winter months, evaporation is negligible, and only a few inches a month occur in spring and fall. When summer evaporation is excluded, the mass balance equation underestimates inflow. If evaporation is included in the mass balance, during the peak of summer, inflow would be cfs greater, based on the calculations in Table 2. Appendix A Page A-4 October 2015

51 Table 2. Conversion of evaporative loss on Upper Bucks Lake to inflow Sources of Error There are several sources of error in the inputs to the mass balance calculations. Daily storage change estimates are based on changes in stage height of the reservoirs. Stage is converted to storage using the historic storage/area/elevation curves. Strong wind can result in the lake water surface building up at the gage and influencing the measurement of stage. In addition, errors in the stage/storage/area tables can result in the misinterpretation of daily storage. For example, when nearly full, a hundredth of a foot error in a stage height reading translates to a computed change of 9 cfs (18 AF) daily inflow. The use of monthly data can minimize this type of error, but daily records require editing (smoothing) to compensate for storage errors. Another source of error is associated with travel time through the river reaches, and additional errors can intrude due to the inaccuracy of stream gages at low or high streamflows. Additionally, the US Geological Survey rounds the reservoir storage values that are reported by PG&E to three significant figures, so when the reservoir exceeds the 100,000 acre foot value, rounding causes steps of 1000 AF which produces additional day-to-day error in storage and therefore in daily inflow via the mass balance calculation. Compensating for Errors with the Unimpaired Smoothing Technique A smoothing process was implemented to compensate for these errors in both the Upper Bucks and Upper Grizzly records. Each of the 12 years of streamflow along with precipitation October 2015 Page A-5 Appendix A

52 depth was plotted against time. Maximum and minimum daily temperatures at the nearby Bucks Powerhouse were printed in tables and referenced when needed to determine if storm events were rain or snow. Spikes and dips in the mass balance flows were adjusted to a central tendency if no precipitation occurred, but streamflow increases associated with storms were retained. The observed streamflow at the USGS gage on Spanish Creek ( , Spanish Ck Ab Blackhawk at Keddie, CA) was plotted along with Bucks or Grizzly flows to further determine the magnitude of storm responses versus streamflow variation due to input errors. An example of unsmoothed flows are shown in Figures 2 (Upper Bucks Creek Watershed) and Figure 3 (Upper Grizzly Watershed). Figure 2. Upper Bucks Creek Watershed mass-balance flow (blue) plotted along with flow in Spanish Creek flow (red) and precipitation (black dots with dashed line) Appendix A Page A-6 October 2015

53 Figure 3. Upper Grizzly Watershed mass-balance flow (blue) plotted along with flow in Spanish Creek (red) and precipitation (black dots with dashed line) The daily variations in flow rate in Upper Bucks Watershed (Figure 2) are much larger than the daily variations in the Upper Grizzly Watershed (Figure 3) due to the much larger size of Bucks Reservoir relative to Grizzly Forebay, and the subsequent effect of minor fluctuations in readings of reservoir levels, as discussed above. Smoothing was done primarily to the descending limb of the hydrograph after storms, during the descending limb after snowmelt, and during the low-flow time during summer. Peaks due to storms were adjusted if they appeared overly large for the magnitude of the related precipitation event and associated temperatures. Examples of the smoothed hydrographs for Upper Bucks and Upper Grizzly Watersheds are shown in Figures 4 and 5. October 2015 Page A-7 Appendix A

54 Figure 4. Upper Bucks Watershed smoothed mass-balance flow (blue), Spanish Creek flow (red), and precipitation (black dots with dashed line) Figure 5. Upper Grizzly Watershed smoothed mass-balance flow (blue), Spanish Creek flow (red), and precipitation (black dots with dashed line) Appendix A Page A-8 October 2015

55 As can be seen from comparing Figures 2 and 3 against 4 and 5, peaks remain the same, and the smoothed line eliminates spikes and the sawtooth pattern. The goal of the hydrograph smoothing was to find a central tendency when possible, and move the smoothed line of daily flows through the middle of the field of spikes or daily variations. The summer low-flow period presented a special challenge. As shown in Figure 6, the mass balance values reached zero and went negative. In comparison, the Spanish Creek values routinely reached the mid-30's in August and fell to the low 20's by the end of the water year. The Bucks raw flows bounced around zero in August and went slightly negative as a central tendency by late September (Figure 6). Figure 6. Upper Bucks Creek Watershed mass-balance flow (blue), Spanish Creek flow (red), and precipitation (dashed purple line) The watershed area above the Spanish Creek gage is six times the area of the Upper Bucks Creek Watershed and the watershed characteristics appear to be somewhat different. Much of the area in the Spanish Creek Watershed is lower and less forested than the Bucks Watershed. As such, flow in Spanish Creek is not a direct representation of the Bucks system but because of its close proximity to the area, it can be used for tracking temporal patterns of flow and assessing maximum values for summer flows in Bucks Creek. Further, anecdotal information from PG&E's field staff documents continuous summer flow in the larger streams feeding Bucks Lake, likely due to deep soils and springs that run throughout the summer. Finally, by not accounting for evaporation, the tendency of the mass-balance product to reach zero or trend negative is not surprising. October 2015 Page A-9 Appendix A

56 For these reasons and based on professional judgment, a data set was created called "Smoothed and Adjusted" wherein the summer flows were adjusted to follow a seasonally declining trend similar to Spanish Creek. The two bounds to this flow were that it could not be negative or exceed Spanish Creek flow values. A similar logic was applied to Grizzly Creek summer flows. It should be noted, however, that due to the smaller size of Grizzly Creek Forebay, inflow calculated for Upper Grizzly rarely went negative and was smoother in general than the raw mass balance data for Upper Bucks. At the request of the Technical Working Group (TWG), the Smoothed and Adjusted data set for Upper Bucks was further adjusted to follow the central tendency and allow summer flow values to approach zero and go negative so that evaporation could be explicitly incorporated. In these flow data, the central tendency was always followed except for cases of obvious instrument error. Spikes and other noise were removed via the smoothing process, and in general, the two data sets are the same during high flow periods, but differ during summer periods when the effects of evaporation are prominent. Evaporation was explicitly added as a loss, which increased summer calculated inflow, and in many years, the result matched the initial Smoothed and Adjusted flow values. In some years, however, flows reached zero or went negative, and at the request of the TWG, a final adjustment was made to the Smoothed and Adjusted flow series to move those negative flows above zero but have them be less than the initial data set. The adjustment periods were: Aug. - Oct., 2003; Oct.-Nov. 3, 2004; Sep Nov. 25, 2005; Jul Feb. 2, 2007; Jun Jan. 2008; Oct. - Dec. 12, 2008, Oct. 2009; Sep. 12, Jan. 18, 2012; Aug Oct This data set was labeled Smoothed and Adjusted/Evap. Derivation of Lower Basin Unimpaired and Regulated s The Smoothed and Adjusted/Evap unimpaired records for the Upper Bucks and Upper Grizzly basins provide the building blocks for generating the regulated and the unimpaired streamflow records use in the IHA analysis. Additional streamflow synthesis was required, however, to generate estimates of unimpaired and regulated streamflow at the confluences of Bucks and Grizzly creeks with the North Fork Feather River. The Smoothed and Adjusted/Evap daily records for the upper basins were extrapolated to the lower basins through the use of Appendix A Page A-10 October 2015

57 proportional area analysis. Based on watershed areas, the synthesized streamflow record for the upper Grizzly subbasin was scaled and added to both the Upper Bucks and Grizzly mean daily flow records to estimate the total and regulated streamflow at the confluences. The record for the Upper Grizzly basin was used to synthesize the Lower Bucks subbasin because it was thought to be more similar in slope, size, and aspect. The unimpaired records for the confluences represent estimates for what the flow would be like if no Project facilities existed, and the regulated records for the confluences represent the flow that is estimated to be present under current project operations, as shown below: Unimpaired Bucks at confluence = Upper Bucks streamflow * Upper Grizzly streamflow Regulated Bucks at confluence = NF82 + NF12 + (0.868 * Upper Grizzly streamflow) Unimpaired Grizzly at confluence = 2.21 * Upper Grizzly streamflow Regulated Grizzly at confluence = NF * Upper Grizzly streamflow The completed synthesized data were combined as per above with the regulated record. This period of flow will be combined with the period to generate the long-term record for analysis by the IHA software and operational modeling. The synthesized unimpaired flow record and the regulated record for the confluences cover the same span of years, and are the input data for the purposes of the IHA analysis. Conclusions Time series of daily flows for Upper Bucks Creek Watershed and Upper Grizzly Watershed based on mass-balance equations were calculated and then smoothed to eliminate daily fluctuations caused by the methodology. The smoothing procedure was graphical in nature, and was based on analysis of precipitation and the effect of temperature, and guided by the flow in the mostly-unimpaired Spanish Creek above Blackhawk at Keddie USGS gage. Most flow adjustments were made to the receding limb of the hydrograph after precipitation and snowmelt, and peak flow values were rarely adjusted. The Spanish Creek flow was selected as an upper limit, and both Bucks and Grizzly flows were adjusted up to vary between 10 and 20 cfs at the end of the summer. Further analysis was done on the Upper Bucks series to evaluate evaporation, and October 2015 Page A-11 Appendix A

58 nine flow periods were reduced from the initial adjusted values after evaluating a data set that left out the Spanish Creek flow target. The final flow series explicitly included evaporation as an adjustment criterion, and summer flows were allowed to go very low but not less than zero. The final Smoothed and Adjusted/Evap data set was then used to estimate unimpaired and regulated flows at the confluences with the North Fork Feather River. Bruce J. McGurk, Ph.D, P.H. #730 McGurk Hydrologic Appendix A Page A-12 October 2015

59 Appendix B BUCKS SYSTEM FACT SHEET October 2015 Bucks Creek Project, FERC Project No. 619 Appendix B

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61 October 2015 Page B-1 Appendix B Bucks Creek Project, FERC Project No. 619

62 Appendix B Page B-2 October 2015