DRAFT Approach and Methodology for Water Balance Estimation Paso Robles Groundwater Basin Model Update

Transcription

1 Approach and Methodology for Water Balance Estimation Paso Robles Groundwater Basin Model Update PREPARED FOR: San Luis Obispo County Flood Control and Water Conservation District April 4, 2013 PREPARED BY: Ground Water Resources Development P.O. Box 220, Claremont, CA P: F:

2 Paso Robles Groundwater Basin Model Update 4-Apr-13 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE CONTENTS 1.0 INTRODUCTION Background Previous Investigations Purpose Scope of Work DATA COLLECTION AND ORGANIZATION WATER BALANCE ESTIMATION Recharge and Discharge Components of the Paso Robles Groundwater Basin Estimation of Groundwater Recharge Components Watershed Hydrologic Modeling Data Needs for Watershed Hydrologic Modeling Land Surface Elevations Soil Types Land Use Precipitation Evaporation Streamflow Surface Diversions Reservoir Operations Wastewater Recharge Crop Coefficients Irrigation Efficiency Construction of Watershed Model Delineation of Tributary Sub-Watersheds and Stream Segmentations. 15 i

3 Paso Robles Groundwater Basin Model Update 4-Apr Pervious and Impervious Land Applied Water Soil Types Precipitation Reservoir Releases Wastewater Treatment Plant Discharges Potential Evaporation Calibration of Watershed Model Recharge Components Deep Percolation of Direct Precipitation Deep Percolation of Streambed Seepage Deep Percolation of Applied Irrigation Water Subsurface Inflow Urban Water and Sewer Pipe Leakage Estimation of Groundwater Discharge Components Groundwater Pumping Agricultural Municipal Small Community Systems Small Commercial Rural Domestic Total Pumping Evapotranspiration by Riparian Vegetation Subsurface Outflow SUMMARY REFERENCES FIGURES and TABLES ii

4 Paso Robles Groundwater Basin Model Update 4-Apr-13 FIGURES No. Description 1 Project Location 2 Hydrologic Soil Types in the Paso Robles Area Watershed 3 Precipitation Station Locations 4 Annual Precipitation Oak Shores Station # ) 5 Annual Precipitation Paso Robles Gage ) 6 Annual Precipitation San Miguel Wolf Ranch ) 7 Annual Precipitation Santa Margarita Booster Gage ) 8 Evapotranspiration Station Locations 9 Historical Daily) Evapotranspiration Paso Robles ) 10 Historical Daily) Evapotranspiration Tablas Creek ) 11 Historical Daily) Evapotranspiration Shandon ) 12 Historical Daily) Evapotranspiration Templeton Gap ) 13 Historical Daily) Evapotranspiration Creston ) 14 Stream Gaging Locations 15 Historical Daily) Streamflow Yerba Buena Creek in Santa Margarita ) 16 Historical Daily) Streamflow Santa Margarita Creek near Santa Margarita ) 17 Historical Daily) Streamflow Salinas River below Salinas Dam near Pozo ) 18 Historical Daily) Streamflow Cholame Creek at Palo Prieta Bitterwater Rd) near Cholame ) 19 Historical Daily) Streamflow Salinas River near Bradley ) ) 20 Historical Daily) Streamflow Nacimiento River below Nacimiento Dam near Bradley ) ) iii

5 Paso Robles Groundwater Basin Model Update 4-Apr-13 FIGURES Continued) No. Description 21 Historical Daily) Streamflow Nacimiento River below Sapaque Creek near Bryson ) ) 22 Historical Daily) Streamflow Estrella River near Estrella ) ) 23 Historical Daily) Streamflow Salinas River above Paso Robles ) ) 24 Historical Daily) Streamflow Santa Rita Creek near Templeton ) ) 25 Historical Daily) Streamflow Salsipuedes Creek near Pozo ) ) 26 Historical Daily) Streamflow Toro Creek near Pozo ) ) 27 Historical Daily) Streamflow Salinas River near Pozo ) ) 28 Wastewater Treatment Plant Locations 29 Tributary Sub-Watersheds of the Paso Robles Area Watershed 30a 30b 31a 31b 32a 32b 1985 Land Use Conditions in the Paso Robles Area Watershed 1985 Irrigated Agricultural Types in the Paso Robles Area Watershed 1997 Land Use Conditions in the Paso Robles Area Watershed 1997 Irrigated Agricultural Types in the Paso Robles Area Watershed 2011 Land Use Conditions in the Paso Robles Area Watershed 2011 Irrigated Agricultural Types in the Paso Robles Area Watershed 33 PRISM Precipitation Adjustment Factors 34 Isohyetal Precipitation Adjustment Factors 35 Reference Evapotranspiration ETo) Zones iv

6 Paso Robles Groundwater Basin Model Update 4-Apr-13 TABLES No. Description 1 Data Inventory 2 Precipitation Stations in the Model Boundary, San Luis Obispo and Monterey Counties 3 Evapotranspiration Stations in the Study Area 4 Streamflow Gaging Stations in San Luis Obispo County 5 Wastewater Treatment Plant Diversion Site Information in Paso Robles Groundwater Basin 6 Paso Robles Groundwater Basin Watershed Model Segmentation 7 Sub-Watershed Land Use Summary 1985) 8 Sub-Watershed Land Use Summary 1997) 9 Sub-Watershed Land Use Summary 2011) 10 Assumed Pervious Percentages for Land Use Categories 11 Crop Coefficients for Crop Groups in San Luis Obispo County 12 Irrigation Efficiencies as Percentages for Crop Groups 13 Distribution of Irrigation System Types as a Percentage 14 Percent of Acreage with Deficit Irrigation stressed) 15 Sub-Watershed Soil Summary 16 Sub-Watershed Designated Precipitation Stations and Precipitation Adjustment Factors 17 CIMIS Monthly Average Reference Evapotranspiration 18 Regression Analysis of Evapotranspiration Data Sets 19 Crop Type Classification for Monterey County 20 Crop Type Classification for San Luis Obispo County v

7 Paso Robles Groundwater Basin Model Update 4-Apr-13 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE 1.0 INTRODUCTION The San Luis Obispo County Flood Control and Water Conservation District District), in coordination with the Modeling Subcommittee 1, is in the process of completing a comprehensive update of the Paso Robles Groundwater Basin Basin) model. The primary objective of the groundwater model update is to provide the District and Basin stakeholders with an updated, accepted tool for simulating Basin response, under current and future conditions, to specific scenarios in order to evaluate management options for addressing the documented groundwater level declines that are persisting locally within the Atascadero sub-basin and the Creston and Estrella sub-areas of the Basin. 1.1 Background As part of the District s and Basin stakeholders continuing efforts toward an improved basin management, a two-phased project Paso Robles Groundwater Basin study) was conducted to provide a better understanding of the Basin s hydrogeology and to develop a water resources planning tool. Phase I of the project was a technical study conducted by Fugro and Cleath 2002) to develop a conceptual geologic and hydrogeologic understanding of the Basin. Results from the Phase I study were used to develop a numerical groundwater flow model of the Basin under Phase II of the project Fugro, ETIC, and Cleath, 2005). The groundwater flow model was developed using the widely accepted MODFLOW software code. The Basin model was developed for the period 1981 to 1997, with the ability to evaluate potential future trends in groundwater flow throughout the Basin. However, the existing groundwater model has issues which have been identified by the original modelers, and by others 2. These consist primarily of model conceptualization and water balance issues. Specifically, the conceptual model developed by the original modelers includes the hydrologic separation of the confined Paso Robles aquifer in the Atascadero area i.e., sub-basin) from the confined aquifer in the rest of the Basin. However, the degree of hydraulic connectivity between these two aquifer systems continues to be subject for debate. The 1 2 Formed by the Steering Committee, which consists of all the stakeholder groups overlying the Basin i.e., District, cities, smaller communities, agricultural interests, landowners, and others), to support efforts to update the Basin model. Gus Yates,

8 Paso Robles Groundwater Basin Model Update 4-Apr-13 water balance issues involve evaluation of rainfall recharge, subsurface inflow, stream-groundwater interactions, agricultural irrigation rates, rural water use, and groundwater storage change. These water balance issues are ultimately linked to a lack of available data; some reflect insufficient model documentation. As part of the current Basin model update and to address the issues with the water balance estimation, the GEOSCIENCE / Todd Engineers Team proposed to replace the existing water balance analysis with a new method. The new water balance estimation is to cover the period 1981 through 2011, and includes: Replacement of the original model s Blaney method for evaluating rainfall recharge with a rainfall-runoff modeling system approach watershed model); Application of recently available California Irrigation Management Information Systems CIMIS) data to assess evapotranspiration losses; and, Analysis of water balance components on a monthly basis, as opposed to a semi-annual basis. The new method extends the water balance from the limits of the groundwater basin to the surrounding watershed of the Paso Robles area. Accordingly, the study area includes the Paso Robles groundwater basin and contributing watershed. 3 The benefits of a watershed approach and application of a watershed model include a comprehensive understanding of the water balance, and validation of the water balance estimations against actual streamflow data at established gages i.e., model-generated versus observed data). 1.2 Previous Investigations The initial approach to estimate the water balance components of the Paso Robles Groundwater Basin was conducted for the years 1981 through 1997 Phase I Report, Fugro and Cleath, 2002). Phase II of the study included using the Basin model to compare the inflow and outflow components with the Phase I results, and provided projected hydrologic budgets for the year 2006 Phase II Report, Fugro, ETIC, and Cleath, 2005). In a subsequent study, Todd Engineers 2009) evaluated and updated the total estimated groundwater pumping for The methodology used by Fugro for the initial water balance estimation consisted of comparing the annual totals for each recharge and discharge term inventory method ) for the period with the annual changes in groundwater in storage specific yield method ). Both methods were used for 3 The water balances of the watershed areas above Salinas, Nacimiento, and San Antonio dams are addressed by examining the reservoir inflows, outflows, and change in storage. 2

9 Paso Robles Groundwater Basin Model Update 4-Apr-13 the seven sub-areas of the Basin and the Atascadero sub-basin see Figure 1). Results from the inventory method indicated that over the 17-year period, the main Basin experienced an average deficit of approximately 2,700 acre-ft per year afy), while the Atascadero sub-basin had no overall change in storage. The specific yield method for the same period resulted in an annual increase in storage of 700 afy for the main Basin, with a slight increase of 200 afy in storage for the Atascadero sub-basin. The differences in annual amounts of changes in storage as calculated by both methods were described as not being unexpected, and likely associated with inaccuracies of some recharge and discharge components, and limitations in the calculations for percolation of precipitation Fugro and Cleath, 2002). The projected 2006 water balance estimation by Fugro 2005) was performed using the calibrated groundwater flow model. Results were comparable with those of the Phase I report i.e., 1997 estimation), however, a higher estimate of inflow and outflow 17%) was projected for The 2009 evaluation by Todd Engineers included analysis of all types of groundwater pumping in the Basin that occurred in Water Year : agricultural, municipal systems, small community systems, small commercial systems, and rural domestic pumping. Each type of pumping demand was calculated using various methods, but in general were comparable to those used for the 1997 estimations. 1.3 Purpose The purpose of this technical memorandum is to present to the District and Modeling Subcommittee the methodology, data, and basis that will be used to update the water balance estimation for the Basin. 1.4 Scope of Work In order to update the water balance, each Basin recharge and discharge component must be evaluated in terms of available data, previous estimates, and its significance to the overall water balance. The recharge components of the water balance will be updated using the results from a rainfall-runoff model, which will be referred to as the watershed model for the Basin. Hydrologic data collected by Todd Engineers from San Luis Obispo and Monterey County departments, and others, will be used to develop the watershed model. The following types of data were collected by Todd Engineers and will be used by GEOSCIENCE / Todd to develop the watershed model and to update the MODFLOW model: 4 A Water Year is representative of the period October 1 through September 30. 3

10 Paso Robles Groundwater Basin Model Update 4-Apr-13 Topography, Soil types, Land uses, Aerial photos, Precipitation, Evaporation, Streamflow, Surface diversions, Wastewater recharge, Crop coefficients, and Irrigation efficiency. Discussion of the sources of data is provided in Section 2. Development of the watershed model will consist of dividing the Basin watershed into sub-watersheds using Geographic Information System GIS) hydrologic modeling. The sub-watershed divisions will be based on topography, drainage pattern, type of stream channel, and location of streamflow gaging stations. Each sub-watershed will consist of a stream segment and either pervious or impervious land surface types. 4

11 Paso Robles Groundwater Basin Model Update 4-Apr DATA COLLECTION AND ORGANIZATION As indicated in Section 1, development of a model involves collection and organization of a substantial body of data obtained from multiple sources. This data collection and organization in itself represents considerable value to San Luis Obispo County and the local stakeholders, recognizing that, once collected and organized, the information can be used for other investigations and as a basis for future data collection efforts. Accordingly, the data compilation effort was systematically tracked in terms of types, sources, responsible data collector, and date of receipt. Data were uploaded onto an online data-sharing FTP) site, organized into a nine main folders organized by major data type: Climate Geology Groundwater Groundwater Model Land Use Soils Surface Water Topography/Ground Cover Wastewater Table 1 provides a summary of the data inventory, including data type, a brief description, source, and FTP folder. 5

12 Paso Robles Groundwater Basin Model Update 4-Apr WATER BALANCE ESTIMATION 3.1 Recharge and Discharge Components of the Paso Robles Groundwater Basin The primary groundwater recharge components are: Deep percolation of direct precipitation, Deep percolation of streambed seepage, Deep percolation of applied irrigation water, Subsurface inflows through the Basin boundary, Deep percolation of discharged treated wastewater effluent, and Recharge from urban water and sewer pipe leakage. The primary groundwater discharge components are: Agricultural pumping, Municipal pumping, Rural domestic pumping, Small commercial pumping, Small community systems pumping, Evapotranspiration by riparian vegetation, and Subsurface outflow. 3.2 Estimation of Groundwater Recharge Components As stated previously in Section 1.1, the existing 5 water balance analysis for the recharge components will be replaced with a new method that uses the results from a calibrated rainfall-runoff model. The new estimations of each component will provide a consistent water balance from 1981 through This method will also improve quantification of the recharge components, spatial and temporal distributions of recharge as a result of changes in land uses over time, and assist in the Basin model calibration on the streambed percolation. The following sections describe the data needs and construction process for the rainfall-runoff model. 5 Current estimations as derived from the 2002 study Fugro, 2002), and subsequent updates by Fugro 2005) and Todd 2009). 6

13 Paso Robles Groundwater Basin Model Update 4-Apr Watershed Hydrologic Modeling A rainfall runoff model of the Paso Robles area watershed, referred to as the Paso Robles Watershed Model, will be developed using the Hydrologic Simulation Program FORTRAN HSPF). HSPF is a successor to the FORTRAN version of the Stanford Watershed Model SWM). The SWM evolved over the period from approximately 1956 through In 1974, work resulted in the widely available codes developed for and with support of the United States Environmental Protection Agency EPA). The most recent release of HSPF is version 12. HSPF is a comprehensive and physically based watershed model that can simulate the hydrology and water quality with a time step less than a day Data Needs for Watershed Hydrologic Modeling Watershed hydrologic modeling requires a variety of data to characterize the water balance and hydrologic processes that occur in a watershed. These data include: 1. Land surface elevations 2. Soil types 3. Land use 4. Precipitation 5. Evaporation 6. Streamflow 7. Surface diversions 8. Reservoir releases 9. Wastewater recharge 10. Crop coefficients 11. Irrigation efficiency Land Surface Elevations Land surface elevations were obtained by using a United States Geological Survey USGS) 10-meter-by- 10-meter digital elevation model DEM) in ESRI ArcMap 10. The DEMs are used to evaluate surface water runoff patterns, and in turn to delineate the watershed and sub-watershed boundaries Soil Types Soil type and distribution in the study area is available from an ESRI shapefile of Soil Survey Geographic Database SSURGO) hydrologic soil group information Soil Survey Staff et al., 2012) see Figure 2). 7

14 Paso Robles Groundwater Basin Model Update 4-Apr-13 There are four basic types of soils under this classification system Group A through D), which are based on soil texture and properties. A discussion of soil descriptions and how they affect infiltration is provided in Section Land Use Information on land use and land cover is available from State and County sources. Data on land use within the study area is available from San Luis Obispo County and Monterey County Agricultural Commissioner s Office ACO) crop reports, DWR land use maps, and County-provided parcel GIS shapefiles. Annual crop reports list acreage and type of agriculture such as animal, field, nursery and seed, fruit and nut, or vegetable); however, no geographic information is provided. These crop reports are available from 1981 through 2011 for both counties. Land use GIS shapefiles from various sources and years were also used to determine the locations for each land use category. These shapefiles include: Riparian vegetation distribution 1994) from the California Department of Forestry and Fire Protection; Vineyard locations from San Luis Obispo and Monterey Counties; San Luis Obispo County crop layers for and from the County Department of Agriculture 6 ; Monterey County ranch maps for 2012; South Central Coast land use ) from the DWR; Information from the City of Atascadero regarding city limits and land use for 2011; Information from the City of Paso Robles regarding city limits and land use for 2011; Land use files used for the Phase II study Fugro, ETIC, and Cleath, 2005) covering San Luis Obispo County for 1985 and 1996, and Monterey County for 1989 and 1997; Land use code changes from 1981 to the present from San Luis Obispo County; Land use coverage for 2001 from United States Department of Agriculture National Resources Conservation Service; San Luis Obispo parcel information from ParcelQuest; and San Luis Obispo general plan with land use codes. 6 Department staff was unable to locate crop layer data for 2003 Trapp, R., personal communication, 29-Jan-13). 8

15 Paso Robles Groundwater Basin Model Update 4-Apr Precipitation Precipitation data were obtained from 32 gaging stations within the model boundary in San Luis Obispo and Monterey counties see Figure 3). Hourly data for 11 stations were downloaded from the National Climatic Data Center NOAA) database. Daily records are available for 16 San Luis Obispo County Flood Control and Water Conservation District FC&WCD) stations, as well as from five Western Weather Group precipitation stations in San Luis Obispo County. Each station has varying periods of recorded precipitation data. Station information is listed in the following Table 2. Annual precipitation for selected stations is shown on Figures 4 through 7. 9

16 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 2. Precipitation Stations in the Model Boundary, San Luis Obispo and Monterey Counties Station Name Station Number Agency/Source Elevation, ft amsl Period of Record Cholame Alley Ranch NOAA Parkfield NOAA Paso Robles NOAA Paso Robles 5 NW NOAA Valleton NOAA Santa Margarita Booster NOAA San Miguel Wolf Ranch NOAA Valleton Wolf Ranch NOAA Paso Robles Municipal Airport NOAA Bradley NOAA Nacimiento Dam NOAA Paso Robles PR1) - Western Weather Group Tablas Creek TAB) - Western Weather Group Shandon SDN) - Western Weather Group Templeton Gap TPG) - Western Weather Group Creston CRS) - Western Weather Group Rocky Butte 703 SLO FC&WCD Hog Canyon 709 SLO FC&WCD Atascadero 711 SLO FC&WCD Salinas Dam 719 SLO FC&WCD Shandon 721 SLO FC&WCD Santa Margarita 723 SLO FC&WCD South Portal 760 SLO FC&WCD Templeton 762 SLO FC&WCD Salinas Dam 94 SLO FC&WCD Santa Margarita Booster Station 95 SLO FC&WCD Black Mountain FAA Radar Station) 186 SLO FC&WCD Dellaganna Ranch 139 SLO FC&WCD York Mountain SLO FC&WCD Creston 211 SLO FC&WCD Creston 52.1 SLO FC&WCD Oak Shores Wastewater Plant 201 SLO FC&WCD

17 Paso Robles Groundwater Basin Model Update 4-Apr-13 In addition to data from the precipitation stations, gridded estimates of monthly and annual precipitation are available in the form of PRISM maps. PRISM Parameter-elevation Regression on Independent Slopes Model) was developed by the National Resources Conservation Service NRCS) National Water and Climate Center NWCC) and the PRISM Climate Group at Oregon State University. Gridded data represents the long-term annual precipitation from Isohyetal contours of long-term annual precipitation from , which were compiled from the USGS, California Department of Water Resources DWR), and California Division of Mines maps and information sources, are also available for comparison Evaporation Evaporation zones and monthly average reference evapotranspiration ETo) values inches/month) for the model area are available from the 1999 California Irrigation Management Information System CIMIS) Reference Evapotranspiration Map for the State of California. The ETo zones displayed on the reference map represent regions of similar climate and vegetation characteristics that are used by CIMIS to define ETo values for water use and irrigation demand estimation. ETo refers to the total evaporative losses evaporation and plant transpiration) from a reference crop, usually a short-turf grass growing with no moisture stress. ETo can be estimated for different crop types by applying a crop coefficient, as discussed in Section In addition to the CIMIS data, daily evapotranspiration data are available for six 7 Western Weather Group stations within the study area see Figure 8). These stations are listed in the following Table 3. Daily evapotranspiration from these sites are shown on Figures 9 through 13. As discussed in Section , the station information was compared to the CIMIS data to assign evapotranspiration values to the model area. 7 A seventh station, Camatta Hills, was also included in the data set from the Western Weather Group; however, coordinates were not provided, and the period of record was significantly less: January 2010 through September

18 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 3. Evapotranspiration Stations in the Study Area Station Name/Location Agency/Source Annual Average ET 1,2 CIMIS ETo Zone Period of Record [in/year] Paso Robles Western Weather Group Tablas Creek Western Weather Group Shandon Western Weather Group Templeton Gap Western Weather Group Creston Western Weather Group Hames Valley Western Weather Group Annual average ET for the period , except for the Hames Valley station. 2 Annual average ET for the Hames Valley station for full years Streamflow Historic daily streamflow data are available from four San Luis Obispo County FC&WCD gages as well as from nine USGS gages downloaded from the National Water Information System webpage) for varying periods of record see Figure 14). Gage station information is provided in Table 4 next page), and historical daily streamflow is shown on Figures 15 through 27. The daily readings from all 13 gages will be used to help calibrate the model, as discussed in Section

19 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 4. Streamflow Gaging Stations in San Luis Obispo County Station Name/Location Station Number Agency/Source Period of Record Yerba Buena Creek in Santa Margarita - SLO FC&WCD Cholame Creek at Palo Prieta Bitterwater Road) near Cholame 3 SLO FC&WCD Salinas River below Salinas Dam near Pozo 8 SLO FC&WCD Santa Margarita Creek near Santa Margarita 15 SLO FC&WCD Salinas River near Bradley USGS NWIS Nacimiento River below Nacimiento Dam near Bradley Nacimiento River below Sapaque Creek near Bryson USGS NWIS USGS NWIS Estrella River near Estrella USGS NWIS Salinas River above Paso Robles USGS NWIS Santa Rita Creek near Templeton USGS NWIS Salsipuedes Creek near Pozo USGS NWIS Toro Creek near Pozo USGS NWIS Salinas River near Pozo USGS NWIS Surface Diversions Information on surface water diversions was obtained from diversion permits available through the State Water Resources Control Board s Public Water Rights Database. Information includes water planning area WPA), permit holder name, diversion source and type, status of permit, and allowable diversions in acre-feet per year. These data will be reviewed to ascertain if any diversions are permitted for uses other than the agricultural, rural domestic, or rural commercial uses that will be assessed based on land use data. The permits also may be revealing about specific well locations, recognizing that most local surface water diversions are probably achieved through stream-side wells Reservoir Operations There are three reservoirs operating in the Paso Robles Groundwater Basin: San Antonio, Nacimiento, and Salinas Reservoirs. Daily releases in cubic-ft per second cfs) are available for all three reservoirs from January 1, 1981 through September 30, The data for the Salinas Reservoir i.e., Santa Margarita Lake) includes information on lake elevation, storage, releases, discharges, and diversions out 13

20 Paso Robles Groundwater Basin Model Update 4-Apr-13 of the basin to the City of San Luis Obispo. In addition, daily deliveries from the Nacimiento Dam i.e., the Nacimiento Water Project) in million gallons per day MGD) are also available for January 1, 2011 through September 4, Delivery data are in the form of daily flow totals from turnouts at Templeton and Atascadero; there are no data for the Paso Robles turnout Wastewater Recharge There are four significant wastewater treatment facilities within the Paso Robles Groundwater Basin that either discharge effluent into the Salinas River channel and/or release wastewater into infiltration percolation) ponds see Figure 28). Average daily effluent flows in MGD, as well as the locations and percolation rates for the infiltration ponds, were obtained for inclusion in the watershed model. Average daily discharge rates in MGD were provided either monthly, yearly, or both for the four main areas of wastewater treatment in the Basin. Site names and information are listed in the following Table 5. Table 5. Wastewater Treatment Discharge Site Information in Paso Robles Groundwater Basin Facility Data Type Period of Record City of Paso Robles WWTP City of Atascadero WWTP Templeton CSD WWTP San Miguel CSD WWTP WWTP Wastewater Treatment Plant CSD Community Services District Daily Average Effluent by Month Daily Average Effluent by Year Monthly Percolation ft) Daily Average Effluent by Month Daily Average Effluent by Year Monthly Percolation ft) Waiting for Data Daily Average by Month Monthly Percolation ft) Waiting for Data , Waiting for Data , Waiting for Data Crop Coefficients The crop coefficient Kc) is a dimensionless number that is used to estimate a particular plant s water requirements in a particular region. Crop coefficients are listed in Table A7 of Appendix A of the San Luis Obispo County Master Water Report 2012). As discussed in the later section on Applied Water ), these county-wide crop coefficients were reviewed and adjusted in light of conditions and agricultural practices in the Paso Robles basin. 14

21 Paso Robles Groundwater Basin Model Update 4-Apr Irrigation Efficiency Irrigation efficiency refers to the percentage of irrigation water beneficially used compared to the total water applied in a region. Estimated irrigation efficiencies for irrigation system types sprinkler or micro) and the current usage of irrigation system types for different crop types are listed in Tables A13 and A14 of Appendix A of the San Luis Obispo County Master Water Report 2012). Comparable information is available for Monterey County in the annual Ground Water Extraction Summary Reports. The estimated irrigation efficiencies for major crop groups alfalfa, nursery, pasture, citrus and deciduous, vegetable, or vineyard) are listed in Table A15 of Appendix A of the San Luis Obispo County Master Water Report 2012) for current conditions. Estimated irrigation efficiencies are also provided for historical conditions in the Phase I Study Fugro and Cleath, 2002) Construction of Watershed Model A rainfall-runoff model of the Paso Robles Groundwater Basin watershed will be developed using the Hydrologic Simulation Program FORTRAN HSPF). HSPF is a successor to the FORTRAN version of the Stanford Watershed Model. The following sections describe the process for construction of the watershed model Delineation of Tributary Sub-Watersheds and Stream Segmentations Sub-watersheds are areas that are assumed to have similar hydrogeologic characteristics. They were created for the Paso Robles Groundwater Basin model with the US EPA BASINS 4.1 program. The program segments the watershed into several sub-watersheds and stream reaches using a delineation tool and a Digital Elevation Model DEM), as well as user-specified outlet locations. The location of these outlets was based on change in channel type and geography. Through this process, 91 sub-watersheds and 91 corresponding stream reaches were defined see Figure 29). A list of the names, drainage areas, and stream reach lengths for each sub-watershed is provided in Table 6. Reaches have the same numbers as the sub-watershed in which they are found. These numbers serve only as identifiers in the HSPF modeling process and do not need to be sequential or continuous. Each stream reach segment was analyzed to determine the hydraulic behavior through the use of an FTABLE hydraulic table). FTABLEs determine the infiltration volume of stream reaches by using the HSPF BMP Toolkit created by the US EPA, which takes into account the lining type all streams in the watershed are unlined 8 ), slope, Manning s Roughness Coefficient used for flow calculations), and the length of the stream reach. 8 All streams within the Paso Robles area watershed have natural channel bottoms. 15

22 Paso Robles Groundwater Basin Model Update 4-Apr-13 Each of the sub-watersheds was assigned model parameter values based on the available data in the area. The assignment process for each parameter is discussed in greater detail in the following sections Pervious and Impervious Land Land use and development affect how water enters or leaves a system by altering infiltration, surface runoff, location, and degree of evapotranspiration, and where water is applied in the form of irrigation. Since land use changes over time, information from 1985, 1997, and 2011 was used to locate and designate areas as being pervious or impervious within the model boundary during the simulation period see Figures 30a, 31a, and 32a, respectively). There are six main land use categories: Agriculture/Parks/Golf Course, Commercial/Industrial/Public Facility, Open Space/Dry Agriculture/Water Body, Residential Low Density, Residential Medium Density, and Residential High Density. As shown on Figures 30b, 31b, and 32b, the Agriculture/Parks/Golf Course category is further broken down into Alfalfa, Deciduous, Nursery, Pasture, Truck, and Vineyard sub-categories for the purposes of assigning crop coefficients and irrigation factors, as discussed in the following Section The acreages of each land use category and sub-category for 1985, 1997, and 2011 are shown in Tables 7, 8, and 9, respectively. The land use category determines to what degree areas are pervious or impervious. Even areas with residential or commercial land use categories are assumed to have a percentage of pervious area associated with them i.e., landscaping). These percentages are listed below for each land use type in Table 10. Table 10. Assumed Pervious Percentages for Land Use Categories Land Use Category % Pervious Agriculture/Parks/Golf Course 100 Commercial/Industrial/Public Facility 20 Open Space/Dry Agriculture/Water Body 100 Residential Low Density 90 Residential Medium Density 50 Residential High Density 40 16

23 Paso Robles Groundwater Basin Model Update 4-Apr Applied Water The Paso Robles Groundwater Basin includes significant areas of both agricultural and developed commercial and residential land. Water is applied to the land differently depending on the land use. Areas designated as being industrial or residential still typically have an applied water value associated with the irrigation of landscape. The model considers both urban and agricultural irrigation practices. The overall approach to simulate applied water in both urban and agricultural irrigation settings is based on the assumption that irrigation systems are used, and that the water is applied in amounts sufficient to satisfy the monthly crop and land evapotranspiration ET) demands that exceed available rainfall. The 2012 Master Water Report analysis ESA, 2010) calculated the crop-specific applied water for crop types by using information on crop evapotranspiration, effective rainfall, leaching requirements, irrigation efficiency, and frost protection. The following equation was used to evaluate annual applied water demand for specific crop types: Annual Crop-Specific Applied Water AF/AC/YR) = ETc Er 1 LR) x IE where, ETc = Crop Evapotranspiration [AF/AC/YR] Er = Effective Rainfall [AF/AC/YR] FP = Frost Protection [AF/AC/YR] LR = Leaching Requirements [%] IE = Irrigation Efficiency [%] + FP Crop Evapotranspiration ETc). The crop evapotranspiration will be calculated by multiplying a specific crop coefficient with the CIMIS reference evapotranspiration ETo) see Section ). For the 2012 Master Water Report, crops were assigned monthly crop coefficients for alfalfa, nursery, irrigated pasture, citrus, deciduous, vegetable, and vineyard crop groups. These coefficients will be used in this model update, with modifications as discussed below, and are reproduced in Table 11 below. It is understood that the UC Cooperative Extension study will yield new information on vineyard water demand and irrigation. 17

24 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 11. Crop Coefficients for Crop Groups in San Luis Obispo County Month Alfalfa Citrus Deciduous Nursery Pasture Vegetables Vineyard January February March April May June July August September October November December In San Luis Obispo County, vegetables are often double-cropped. This was assumed in the 2006 Pumping Update and in the Master Water Report. However, the Phase I Study assumed one vegetable crop per year. Specific truck crop types e.g., carrots, melons) are not indicated in the recent maps. However, discussion with Upper Salinas/Las Tables RCD staff indicates the presence of lettuce, spinach, carrots, and various vegetables for farmers markets. Consideration of frost potential in the study area suggests one truck crop per year between April and October; for the purpose of this model update, the vegetable crop coefficient 1.00) is adopted from the Master Water Report and applied to the months of May through September. Irrigation Efficiency. The Phase I Study p. 129) presented a table of assumed efficiencies by crop category and by five-year periods from 1980 through The 2012 Master Water Report Appendix A, p ) evaluated irrigation efficiency through literature review and consultation with Central Coast RCD staff, growers and other stakeholders in San Luis Obispo County. This analysis considered irrigation system types sprinkler and micro) for the crop categories and distribution uniformities. Existing efficiencies are expressed as low and high values for the crop categories. Low and high project efficiencies also are provided for the future; these are uniformly five percent higher than existing values. For the purposes of this evaluation, average efficiencies also were computed. Comparison of the Phase I Study values for 1980 through 1997 and the Master Water Report s existing 18

25 Paso Robles Groundwater Basin Model Update 4-Apr-13 and future values indicates a general consistency, with efficiency generally increasing over time. When plotted over time, the computed average values for existing and future conditions provided the smoothest fit to the trend of preceding Phase I Study values. For the purposes of this model update, irrigation efficiency values need to be considered as they have changed over the study period. First, the five-year irrigation efficiencies developed in the Phase I Study are retained in the evaluation of agricultural pumping from 1981 through Second, the computed average values for irrigation efficiencies from the 2012 Master Water Report are used to represent existing conditions with modifications as described below). For the years between 1997 and the end of the study period, a linear trend in irrigation efficiency is generally assumed for each crop. Consistent with the Phase I Study, the period between 1997 and 2011 can be divided into five-year segments e.g., , , and ). It should be recognized that improving efficiency is or will be) increasingly difficult and costly, and that the rate of improvement necessarily levels off, never to reach 100 percent. While the irrigation method for example, conversion from sprinklers to drip or micro systems) is not the sole means of water conservation, it has been a major factor. Review of available information on irrigation systems in the Salinas Valley MCWRA, 2011) indicates that the percentage of vineyards on drip has increased from 80 percent in 1997 to 97 percent in 2007 and 98 percent in The San Luis Obispo 2012 Master Water Report similarly concludes that 100 percent of vineyards currently use micro irrigation systems. It can be assumed that the rate of efficiency improvements probably has leveled off in recent years e.g., after 2007) and will continue to flatten in the future. Accordingly, the average efficiencies for recent and future vineyards will be adjusted. Table 12 below presents assumed efficiency values for major crops from the Phase I Study for the five-year periods from 1980 through For the current period ) and the future, the values were developed from the average, adjusted efficiency values for existing and future conditions from the 2012 Master Water Report. For the intervening periods and ), the values are interpolated, and in the case of vegetables, show a leveling off in the rate of efficiency improvement. Efficiency values are indicated to be stable for alfalfa and pasture. Urban irrigation is typically limited to lawn watering by homes and businesses. As such, the dominant vegetation is assumed to be turf grass, which has a crop coefficient of 0.6 from AQUA TERRA, 2003). In addition, an irrigation efficiency of 85% will be used from AQUA TERRA 2003), which corresponds to a well-designed and well-operated sprinkler irrigation system. 19

26 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 12. Irrigation Efficiencies as Percentages for Crop Groups Phase I Study) Crop Group Future Truck/Vegetable Pasture Alfalfa Vineyard Deciduous Nursery With regard to geographic variability, it is assumed that Master Water Report countywide values are reasonably representative of the Paso Robles Basin. Moreover, the San Luis Obispo County values are extended to the Monterey County portion of the basin. This extrapolation is supported by comparison of the usage of irrigation system types in the two counties. The 2012 Master Water Report Appendix A p. 12) documents the percentage of acreage with sprinkler and micro irrigation systems; similarly, the MCWRA 2011 Ground Water Summary Report MCWRA, 2011) documents the acreage of sprinkler systems and drip systems in Salinas Valley. The irrigation system distribution of major comparable crop types summarized in Table 13 below shows that the use of irrigation systems is very similar. This suggests comparable irrigation practices throughout the basin and across the County line. Table 13. Distribution of Irrigation System Types as a Percentage Crop Group Monterey County San Luis Obispo County Drip/Micro Sprinkler Other 1 Drip/Micro Sprinkler Other 1 Truck/Vegetable Forage/Pasture/Alfalfa Grapes/Vineyard Tree Crops/Deciduous Other includes combinations, furrow, and surface irrigation Vineyard Canopy Development. Water use by a vineyard varies with climate conditions and with the size of the vineyard canopy Prichard, et al., no date). In general, the larger the canopy, the greater the 20

27 Paso Robles Groundwater Basin Model Update 4-Apr-13 water use. Seasonal canopy growth is accounted for in the crop coefficient for vineyards, which begins as a small value after bud break, increases as the canopy expands in spring and summer, and then decreases in autumn. However, there are other factors in canopy extent, including the design of the vineyard row spacing and trellis design) and the age and condition of the grapevines. Vineyards with wider spaced rows, young grapevines or low vigor vines with a small canopy use less water on a per- acre basis than vines with a larger canopy Prichard, et al., no date). It is noted that many vineyards are managed with Regulated Deficit Irrigation RDI) methods, in which water application is restricted and the growth of the canopy is managed; this is addressed in a subsequent section. With regard to vineyard design, it is recognized that this can be a significant factor in the water consumption on a vineyard basis. For example, the water use with a VSP trellis with 9-foot row spacing has been estimated to be about 60 percent of the water use of a high density planting Williams, 2001). On a regional scale, this could be significant to an evaluation of agricultural pumping if there were a predominance of low-water or high-water use vineyard designs in a subarea or a strong trend over time. A trend toward smaller row spacing e.g., higher density of grapevines) has been noted in the Central Coast Bettiga, 2013). At this time, data are not readily available on vineyard designs. Accordingly, this factor is not quantified for this model update, but should be considered in the future. Similarly, data are not available on the health of vineyards and this factor is not considered here. However, the age of vineyards was considered in the Phase I Study, which reviewed available crop map data to estimate vineyard ages in four categories: first year, second year, third year, and mature. These were assigned percentages of normal ETc, respectively: 20, 60, 80 and 100 percent. For the purpose of this model update, this analysis is retained for the period of the model and also is extended to the period using the annual San Luis Obispo County crop maps and available Monterey County mapping. Regulated Deficit Irrigation. Regulated deficit irrigation RDI) refers to the practice of regulating or restricting the application of irrigation water to a vineyard, thereby limiting the vine water use to below that of a fully watered vine Prichard, et al., no date). The objectives are to improve the quality of the grape, control growth of the canopy, manage grape yield, and conserve water. Regulated deficit irrigation was not addressed in the 2012 Master Water Report. However, its importance was noted in recent water balance studies Yates, 2010). This practice was recognized in the Phase I Study and termed as intentional water stress. The Phase I Study subdivided vineyard acreage into normal and stressed and assumed that only third-year and mature vineyards were subject to stressing RDI). Stressed vineyards were assumed to experience a 30 percent reduced ET. The adoption of this irrigation technique was recognized as increasing at a constant rate of 15 percent every five years 21

28 Paso Robles Groundwater Basin Model Update 4-Apr-13 from 0 percent of vineyard acreage in to 30 percent in , and then reaching 35 percent in the last two years, For the purposes of this model update, the 30 percent reduction in consumptive use is applied to thirdyear and mature vines and is assumed throughout the entire study period and distributed evenly through the growing season. This is a simplification of an irrigation technique that is dynamic and highly adaptive to various vineyard conditions. With regard to timing, RDI can be applied as a consistent reduction or may be varied over the irrigation season to manage the vine s response Prichard, no date); the latter is beyond the scope of this evaluation. Nonetheless, a 30 percent reduction to 70 percent of full ET is a reasonable estimate within a range of practices e.g., 60 to 80 percent, Bettiga, 2013). It is also reasonable in light of literature addressing the effect of RDI on grape berry size, yield, and quality in the range of 75 to 80 percent of full vine water use Williams, 2001; Prichard, no date). Significantly less water results in yield reductions, but full potential water use maximizes canopy growth and reduces the quality of the subsequent wine. The estimated expansion of this technique in five-year increments from 1981 through 1997 is retained for the evaluation of pumping. For the subsequent period, the constant-rate increase from through is projected in five-year increments to 2011 Table 14). This results in a current estimate of 75 percent. This value is in reasonable agreement with a recent survey in San Luis Obispo County that indicated use of RDI by 83 percent of survey respondents Beal, 2011), presuming that survey respondents as compared to the total grower community) are more likely to be engaged in state-of-the-art irrigation practices. Table 14. Percent of Acreage with Deficit Irrigation stressed) Paso Basin Study Phase I* Projected Percent Acreage *Interim value not shown, 35% Effective Rainfall ER). Effective rainfall is the amount of rainfall that occurs on a crop and is used effectively for the crop s water demand. Previous estimates of effective rainfall have involved application of rainfall on a seasonal or annual basis. The Phase I Study pp ) evaluated the distribution of rainfall across the basin, estimated a representative soil moisture holding capacity, and applied relationships between gross rainfall and crop water use to estimate effective rainfall on a semiannual basis. The 2012 Master Water Report estimated ER by applying a range of low and high percentages for each crop type to a local average annual rainfall e.g., Paso Robles total of 15 inches.) These values range from about 30 to 60 percent, suggesting the importance of effective rainfall. 22

29 Paso Robles Groundwater Basin Model Update 4-Apr-13 For this model update, we note that, assuming a perfect irrigator, effective rainfall represents a direct, commensurate reduction in irrigation pumping. It also depends on the timing and intensity of rainfall, soil moisture conditions, and crop growth, which change at least) on a daily basis. Recognizing this, we will prepare daily soil moisture balances that account for daily rainfall, ETc, and soil moisture, and thereby provide an estimate of effective rainfall on a daily basis. Frost Protection FP). Frost protection was addressed in the Phase I Study pp ) by assuming 11 nights with frost in March and April, an application rate of 0.5 AF/AC/YR, and use of frost control by 50 percent of vineyards. The 2012 Master Water Report analysis in Appendix A pp. 9-11, ESA, 2010) evaluated sprinkler frost protection water requirements for vineyards throughout the County; this method was reviewed for application to this model update. Water is used for frost protection of vineyards generally from bud break in March through April recognizing that bud swell is also a vulnerable period, that bud break varies, e.g., with location and varietal, and that frosts can occur in May). Because of the short-term need for copious spraying, the water typically is pumped from a reservoir which in turn is supplied from a well). Use of sprinkler frost protection is also predicated on the risk of frost, which typically is greatest in low-lying areas of poor air drainage, and on availability of a reservoir. In estimating agricultural pumping, the frost protection value ESA used was 0.25 AF/AC/YR for vineyards throughout the County. This was based on information provided by the UC Farm Advisors and input from the WRAC and other agricultural stakeholders. The value was based on overhead sprinkling for four to six hours per night for 10 to 12 nights per year with an assumed system flow rate of 50 gpm/ac. Using these estimates resulted in a range of annual application rates from 0.34 to 0.62 AF/AC/YR see Table A11 in Appendix A, Carollo, 2012). Taking a representative value of 0.5 AF/AC/YR, ESA assumed that approximately 50 percent of the vineyards use frost protection. Therefore, ESA used 0.25 AF/AC/YR for annual vineyard frost protection on a regional basis. For this model update, review focused on the number of nights with frost, the timing of frost protection during the year, and the geographic distribution of frost protection. Consultation with Central Coast viticulture experts Larry Bettiga and Mark Battany) indicates that the estimate of 10 to 12 frost nights per year is overstated. Hames Valley is relatively frost-susceptible and 10 nights is a reasonable albeit high value for that area. The San Luis Obispo portion of the study area has fewer frost nights, especially in recent decades. More accurate quantification of frost nights would involve analysis of hourly temperature data from the climate stations; such an effort is beyond this scope of work. For this estimate of agricultural pumping, the approach of the 2012 Master Water Report is retained as conservative i.e., overstating water application). However, the low-end values are used 23

30 Paso Robles Groundwater Basin Model Update 4-Apr-13 ranging from 0.34 to 0.52 AF/AC/YR as shown in Table A11 in Appendix A, Carollo, 2012), resulting in a reduced frost protection value of 0.4 AF/AC/YR. Readily available information on minimum temperatures in Paso Robles Battany, 2011) indicates that freezing temperatures can occur from March into May and even June. Frost protection also is used in late September and October in Hames Valley Bettiga, 2013). For the purposes of this model update, water use for frost protection is distributed to the two months, March and April, when frost protection is most likely to be needed. Accordingly, estimated frost protection is 0.2 AF/AC/YR for each month; it is assumed to be needed every year. Frost protection is used in some areas and not others; for example, vineyards in the San Luis Obispo County portion of the study area west of Highway 101 typically do not practice sprinkler frost protection because of lack of available water Battany, 2013). As noted previously, low-lying areas are more susceptible than sloping land. Several ways are available to address the geographic distribution of frost protection across vineyards, including assumption of an even distribution across all vineyards e.g., at the previously used 50 percent rate, or linking the distribution to proximity to holding ponds, which are visible on aerial photographs along with large pumps and can be assumed reasonable to serve adjacent fields. For this model update, the latter approach will be applied. It is noted that frost protection is most significant for gross agricultural pumping. With regard to agricultural consumption, frost protection results mostly in return flows; ET consumption is limited to short-term evaporation from wet soil. Heat Protection. Heat protection involves use of sprinklers to reduce heat stress, for example, on vineyards. This practice in not widespread in the Paso Robles area and is not considered further for this model update. Leaching Requirements LR). Leaching requirements for the Paso Robles Basin were presented in the Phase I study pp ). This study addressed crop-specific threshold salinity, regional groundwater quality, and rainfall, and focused on vineyards in the eastern portions of the basin Shandon, Camatta Canyon, San Juan Creek). In the 2012 Master Water Report Appendix A, p. 11), ESA used these estimates, approximately five percent to 16 percent for different crops, to estimate current annual LR for the crop groups in inland areas. To account for build-up of salts in the soil, ESA assumed that future leaching requirements would be one to two percent higher than existing leaching requirements. Consideration of leaching requirements for this model update focused on vineyards, which are the most sensitive of the local crop categories, the amount and timing of water application for leaching, and any geographic variability. Consultation with the Central Coast viticulture experts Larry Bettiga and Mark 24

31 Paso Robles Groundwater Basin Model Update 4-Apr-13 Battany) indicates that the application of water for salt leaching is variable, depending on the local soil and water quality, irrigation system, and grower s practices. A survey of soil salinity status Battany, 2007) in central Paso Robles basin vineyards generally in the Estrella, Shandon, and Creston sub-areas) indicates that soil salinity is below general levels of concern for most vineyards. However, in some vineyards, soil salinity conditions are at levels that can adversely impact vineyard growth and yield. Elevated soil salinity appears more pronounced in the western portions of the survey area Figure 6 in Battany, 2007). The presence of local elevated soil salinity does not necessarily mean that soil leaching is being practiced; in fact, it suggests that soil leaching is inadequate to manage soil salinity in the long term. With regard to the amount of water application for soil leaching, the estimates developed in the 2002 Phase I Study and adopted in the 2012 Master Water Report are reasonable recognizing the current lack of data and the considerable local variation). However, the values may be too high, given trends toward increasing soil salinity levels that suggest insufficient salt leaching Battany, 2013). For the purposes of this model update, the leaching values in the 2012 Master Water Report are retained for vineyards and the other respective crop types. With regard to geographic variability, the amount of water needed not necessarily applied) for long-term effective salt leaching can be computed based on the specific crop sensitivity, local soil salinity, and applied water quality which varies across the basin). With the compilation of water quality data for the current Salt and Nutrient Management Plan process, such an analysis should be conducted in the future, but is beyond the scope of this model update. For the purposes of this update, the leaching values in the 2012 Master Water Report are retained and are assumed to be applicable to the respective crop types across the basin. The Phase I Study and the 2012 Master Water Report considered leaching requirements on a semi-annual or annual basis, while this model update considers pumping including leaching requirements) on a monthly time step. Consultation with the Central Coast viticulture experts indicates that water is not applied for leaching during the growth season; during this period, growers practice careful deficit irrigation in order to manage the growth of the vineyard canopy and the quality of the grapes. Some growers may pre-irrigate vineyards, in part for salt leaching, especially if the preceding winter was dry. However, the common local practice with deficit irrigation is to allow the soil moisture to be depleted during the course of the growing season, and then apply a post-harvest irrigation that provides leaching Battany, 2013). For the purposes of this model update, it is assumed that pumping and application of water for leaching occurs in October. Moreover, it is recognized that rainfall in a wet year provides salt leaching, and that growers probably would not choose to provide additional leaching in the subsequent season. For the sake of 25

32 Paso Robles Groundwater Basin Model Update 4-Apr-13 methodological simplicity, the rainfall amount in the preceding season is not addressed in the agricultural pumping estimate, and it is assumed that salt leaching occurs every year. As with frost protection, it is noted that water application for salt leaching is most significant for gross agricultural pumping. The intent of salt leaching is for the water to percolate and drive salts downward through the soil. Accordingly, most of the water is returned, except for short-term evaporation from wet soil Soil Types In addition to land use, soil type and distribution also affect infiltration, surface runoff, interflow, groundwater storage, and deep groundwater losses. As mentioned previously, there are four main hydrologic soil groups, all of which are present in the model area. SSURGO describes each type as the following: Group A soils have a high infiltration rate low runoff potential) when thoroughly wet. They consist mainly of deep, well drained to excessively drained sands or gravelly sands and have a high rate of water transmission. Group B soils have a moderate infiltration rate when thoroughly wet. They consist mainly of moderately deep or deep, moderately drained soils that have moderately fine texture to moderately coarse texture and have a moderate rate of water transmission. Group C soils have a slow infiltration rate when thoroughly wet. They consist mainly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. They have a slow rate of water transmission. Group D soils have a very slow infiltration rate high runoff potential) when thoroughly wet. They consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. Therefore, they have a very slow rate of water transmission. A relative infiltration rate is associated with each soil group, ranging from soils with a high infiltration rate characteristic of coarser sediments Group A) to a very low infiltration rate characteristic of finer-grained materials Group D). The extent to which each sub-watershed is covered in these soil types was determined through GIS and these values are listed in Table 15. Each sub-watershed is given an average infiltration index based on the percentage of the various soil types within its borders. HSPF uses a soil index coefficient of four for Group A soils, three for Group B, two for Group C, and one for Group D. These index coefficients are multiplied by the area percentage of 26

33 Paso Robles Groundwater Basin Model Update 4-Apr-13 each soil in each sub-watershed, and then summed to yield the average infiltration index value for that particular sub-watershed Precipitation Precipitation adjustment factors were assigned to each sub-watershed. These factors will be used to determine average daily precipitation values for each sub-watershed based on the precipitation recorded at select stations in the model area. Four precipitation stations were chosen for the calculation of the adjustment factors, and will also be used for future assignment of daily values based on the completeness of the data record and their spatial distribution within the Paso Robles Groundwater Basin. The selected stations include: the Oak Shores Wastewater Plant Station 201), San Miguel Wolf Ranch Station 47867), Paso Robles Station 46730), and Santa Margarita Booster Station 47933) see Figure 33). The process of calculating the precipitation adjustment factors for each sub-watershed involved the following steps: An average annual precipitation value was determined by averaging the PRISM grid values for each sub-watershed. The average annual precipitation value from the PRISM grids for each select precipitation station was noted. The averages within each sub-watershed were compared to the averages of the select precipitation stations. The station with an average annual precipitation value closest to each individual sub-watershed will be used to assign daily values. The precipitation adjustment factor was then calculated by dividing the average annual precipitation value for each sub-watershed by the average precipitation value of the station that was designated as being the closest match in terms of long-term average precipitation PRISM values). Historical daily precipitation values for each station will then be multiplied by the precipitation adjustment factor to determine daily precipitation within each sub-watershed. The same method above was used to analyze the long-term annual average precipitation values from the isohyetal contours with an additional initial step of gridding the data in GIS) see Figure 34). However, since the PRISM data set contains annual precipitation values spanning the model simulation period, it was chosen in preference to the isohyetal contours to calculate the precipitation adjustment factors for each sub-watershed. Precipitation adjustment factors and designated precipitation stations are listed in Table

34 Paso Robles Groundwater Basin Model Update 4-Apr Reservoir Releases As noted previously, the watershed areas above the major reservoirs are addressed by examining reservoir operations data. Accordingly, diversions from Santa Margarita Lake/Salinas Dam are exported from the watershed and Nacimiento Project Water deliveries are incorporated into the groundwater model as municipal recharge and return flows. Water releases from the Nacimiento, San Antonio, and Salinas Reservoirs represent an external source of water coming into the watershed model area. As such, they are included as input to the watershed model to help establish a water balance Wastewater Treatment Plant Discharges The four wastewater treatment facilities listed previously in Table 5 also represent a source of external water in the water balance equation. The effluent releases from each facility are included in the watershed model while recharge from percolation ponds will be included in the groundwater portion of the model Potential Evaporation Monthly evapotranspiration rates were applied to the sub-watersheds based on which CIMIS ETo Zone the centroid of each sub-watershed is located within see Figure 35). Daily evapotranspiration values are assumed to be constant within each month. The CIMIS ETo values for the ETo Zones within the model area are reproduced in Table 17 below. 28

35 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 17. CIMIS Monthly Average Reference Evapotranspiration Month ETo Zone 6 ETo Zone 10 ETo Zone 16 [in/month] [in/month] [in/month] January February March April May June July August September October November December TOTAL To ensure that the method described above is valid, the monthly CIMIS reference evapotranspiration rates were compared to the monthly evapotranspiration rates compiled from daily data) from the five Western Weather Group stations within the model area. A regression analysis was performed to determine how closely the two data sets matched. This was done using the RSQ Function in Excel, which returns an r-squared value which is representative of the proportion of the variance in y that is attributable to the variance in x 1.00 corresponds to a very good fit). Based on the analysis, the r-squared values at each station ranged from , indicating that the CIMIS data is a good fit for the observed. These results are provided in Table 18. Bare Soil Evaporation. The Phase I Study addressed the evaporation from wet soils. Subsequent peer review Yates, 2010) suggested that bare soil evaporation was overestimated by a factor of two and recommended application of a more rigorous technique Allen et al., 1998). Bare soil evaporation will be accounted for in the watershed model 29

36 Paso Robles Groundwater Basin Model Update 4-Apr-13 Cover Crops. Since the 1990s, cover crops have been widely used in vineyards Battany, 2013). A major objective is to manage the soil erosion that can occur with intense rainfall or use of sprinklers for frost protection. Other potential benefits include dust control, weed suppression and an increase in soil organic matter Bettiga, 2013). Cover crops may involve grasses such as brome or fescue) that are allowed to self-seed, or grains e.g., barley) or legumes that are planted. The cover crops generally grow in the winter and spring e.g., November through March), relying on rainfall. In early spring, the cover crops typically are mown and allowed to senesce through the dry season, or are tilled. Mowing or tilling of cover crops may coincide with bud break in order to reduce the risk of frost damage by exposing the soil to solar heating. In water-short areas of the Central Coast, farmers are aware that growing cover crops involves added water consumption. However, cover crops also reduce runoff and promote infiltration Bettiga, 2013). As summarized in the literature Smith, et al., 2008), it is recognized that competition between vines and cover crops for soil moisture in spring could result in water stress that reduces grape production. This concern is less with wine-grape production because water stress may be induced to enhance wine quality i.e., deficit irrigation). Growers in dry portions of Monterey County Smith, et al., 2008) reduce the water consumption by using narrow cover-crop strips e.g., 32 inches wide). It is recognized that: 1) the use of cover crops has increased over time, 2) the type of cover crop varies, 3) the growth of cover depends on rainfall, and 4) the areal extent of cover varies with row spacing and other vineyard-specific factors. For this model update, we assume the following: all vineyards have cover crops beginning in the 1990s, the cover crop is a grass or grain, the cover crop is present and growing from November through March, and the coverage within the vineyard is 60 percent Calibration of Watershed Model After the Paso Robles Groundwater Basin watershed model is developed, the model will be calibrated against measured streamflow data for the period January 1, 1981 to December 31, Data from all 13 gaging stations discussed in Section will be used. Model calibration will be performed in accordance with guidelines provided by the United States Environmental Protection Agency U.S. EPA, 2000). The calibration process involves adjusting model parameters until the model provides a reasonable match between the simulated and measured water balance and a good fit between the simulated and measured daily and monthly streamflow. The qualitative calibration results will be shown as: Hydrographs of measured and model-simulated daily streamflow; 30

37 Paso Robles Groundwater Basin Model Update 4-Apr-13 Hydrographs of measured and model-simulated monthly streamflow; Scatterplots of measured versus model-simulated daily streamflow; Scatterplots of measured versus model-simulated monthly streamflow; and Exceedance Probability Curve of measured and model-simulated daily streamflow Recharge Components Recharge components include all components of the watershed hydrology which represent inflow terms in the basin water balance. Recharge will occur as a result of deep percolation of direct precipitation falling on the basin; deep percolation from seepage occurring in the streambeds, deep percolation from applied irrigation water in agricultural application as well as return flows from irrigation and operations in rural domestic, small system, small commercial e.g. wineries). Recharge to the ground water basin also comes from subsurface inflow from outside the basin but within the watershed and from operational losses from water distribution systems and sewer systems Deep Percolation of Direct Precipitation The quantity of water that will recharge the ground water aquifer as a result of the deep percolation of direct precipitation will be calculated by the watershed model based on input parameters discussed in Section and on the historical hydrology and land use in the ground water basin Deep Percolation of Streambed Seepage The quantity of water that will recharge the ground water aquifer as a result of the streambed seepage will be calculated by the watershed model based on input parameters of the physical characteristics for each of the stream reaches of the watershed and in consideration of the historical hydrology. Input parameters such as channel geometry, soil type and infiltration rate will reflect the specific site conditions along the stream reaches providing spatial and temporal distribution of recharge within the watershed Deep Percolation of Applied Irrigation Water Return flows from agricultural application can be a significant portion of the basin water balance both in volume and in ground water quality. The amount of return flow is directly related to ground water pumping, irrigation practices, and hydrology. Therefore the quantity of return flow recharge to the ground water system) from agricultural water will be calculated using the watershed model and will based on input parameters developed for this study for applied water in the watershed. Included in this 31

38 Paso Robles Groundwater Basin Model Update 4-Apr-13 estimation will be return flows from rural domestic, small system, and small commercial operations based on a percentage of surface applied water and land cover Subsurface Inflow The Phase II report estimated the subsurface inflow to the ground water basin from the surrounding bedrock areas along the margins of the ground water basin as follows: The inflow was input as a region of recharge wells along the margin of the basin in Model Layer 4 Figure 31). Minor modifications were made during the calibration process to increase groundwater elevations in areas of the Atascadero subbasin, Creston, and San Juan areas. accounted for less than a 400 AFY increase in recharge into the basin. These changes Areas of elevated local subsurface inflow were added where the groundwater model required significant additional recharge that was not accounted for in the Phase I Report hydrologic budget. These areas were identified during model calibration as areas where insufficient inflow was available to simulate the measured groundwater elevations. These areas were simulated in the groundwater model using a head-dependent boundary condition Figure 31). Specifically, these areas were simulated by: A MODFLOW constant head boundary with an elevation of 1,425 feet above mean sea level amsl) in the Creston area. A MODFLOW constant head boundary with an elevation of 1,425 feet amsl in the area north of Paso Robles. A MODFLOW general head boundary with an elevation of 1,450 feet amsl in the South Gabilan area. For this model update, the subsurface inflow will be determined from the watershed model. Subsurface inflow is the deep percolation from precipitation for the area outside the ground water basin but within the watershed Urban Water and Sewer Pipe Leakage Operational losses from water distribution located within the ground water basin that represents a recharge component in the basin water balance is quantified through obtaining reasonable estimates of 32

39 Paso Robles Groundwater Basin Model Update 4-Apr-13 unaccounted water from water purveyors. Losses from sewer systems will be assumed to be a small percentage. 3.3 Estimation of Groundwater Discharge Components Groundwater discharge components include: groundwater pumping, evapotranspiration by phreatophytes, and subsurface discharge. The methodology to evaluate each of these components is described in the following sections Groundwater Pumping Of the outflow components, groundwater pumping is by far the largest. For the purposes of evaluation, groundwater pumping is subdivided into agricultural, municipal, small community, small commercial, and rural domestic pumping Agricultural Agricultural groundwater pumping is the largest outflow, with significant trends over time, and considerable uncertainty because it is not metered and/or data are not publically available. It is noteworthy that Monterey County Water Resources Agency e.g., MCWRA, 2011) provides metered water application amounts AF/AC/YR) by crop type e.g., vineyard, vegetable, etc.) for the Upper Salinas Valley from south of Greenfield to the county line). The Upper Salinas Valley is just north of the study area, with somewhat different climate conditions. Nonetheless, the agricultural pumping data available for 2005 through 2011) should be reviewed as an independent check on agricultural pumping estimates for the Paso Robles Basin. Given the lack of agricultural pumping data in the study area, monthly agricultural pumping is estimated based on aerial cropping patterns through time and crop water demand values, adjusted to estimate applied irrigation rates. This basic methodology was developed in the Phase I Paso Robles Groundwater Basin Study Fugro and Cleath, 2002) and used most recently in the San Luis Obispo County Master Water Report Carollo, 2012), documented in Appendix A to that report ESA, 2010). These two references are considered important stepping stones toward this model update; the following sections assume familiarity with or ready access to these documents. The available data on areas of specific crops over the study period include the historical DWR crop maps documenting crops for 1984 and 1995 in San Luis Obispo County and 1989 and 1997 in Monterey 33

40 Paso Robles Groundwater Basin Model Update 4-Apr-13 County. The 1995 and 1997 maps were available in digital form for the Phase I study, and the 1984 and 1989 maps were digitized for the Phase II study Fugro, ETIC, and Cleath, 2005). In the Phase II study, the available land use data were applied by subdividing the base period into two parts Fugro, ETIC, and Cleath, 2005, p. 14): the period 1981 through 1989 was based on the 1984/1989 crop maps and the period 1990 through 1997 was based on the 1995/1997 maps. The land use areas were assumed constant through these intervals. The location of pumping wells was based in the Phase II study on the County s 1990 well location maps, land use maps, and a field reconnaissance Fugro, ETIC, and Cleath, 2005, p. 17). For areas with irrigated agriculture but no known well location, the well was assumed to be located in the center of the agricultural field. The vertical distribution of pumping among aquifer zones was based on review of DWR water well drillers reports to discern agricultural well characteristics, including depth, screened interval, and screened formation Fugro, ETIC, and Cleath, 2005, p. 17). This areal and vertical allocation of pumping was maintained for the portion of the study period. For the period 1997 through 2011, DWR crop maps are not available. However, GIS data on the distribution of crops is available in Monterey County for the year Crop type categories present in the study area are listed in the following table. Several of the categories indicate more than one crop type e.g., alfalfa, wine grape). If data are not available from Monterey County to distinguish crop acreages, available aerial photographs will be examined and the respective crop acreages will be estimated. Table 19. Crop Type Classification for Monterey County Category Alfalfa, Wine Grape Alfalfa, rotational Apple Blackberry Wine Grape, rotational Wine Grape, uncultivated Olive Potato, Carrot, rotational Rotational Walnut, rotational Consistent with the above methodology, the 1997 Monterey County cropping patterns will be assumed constant through 2004, and the 2012 cropping patterns will be assumed constant for 2005 through

41 Paso Robles Groundwater Basin Model Update 4-Apr-13 For San Luis Obispo County, annual land use maps are available from 1996 through 2011 as GIS layers. Given that the pumping allocation already was completed through 1997 with extrapolation of 1995 data), the annual San Luis Obispo County maps will be used from 1998 through The 1996 and 1997 crop maps will be compared with the 1995 DWR map to identify areas of significant change and make adjustments if needed. As before, the location of unknown wells will be assumed in the center of the respective field. The vertical distribution of pumping among aquifer zones will be based on review of the characteristics of nearby agricultural wells including depth, screened interval, and screened formation), with adjustments for documented depths to groundwater, vertical extent of aquifer zones, and depth to bedrock. The San Luis Obispo County GIS crop maps are based on information from the pesticide use records obtained by the County Department of Agriculture. It is understood that the annual GIS crop maps represent planned acreage, with an estimated accuracy of about 80 percent see ESA, 2010, p.13 citation of Mike Isensee, Agricultural Commissioner). The GIS maps document the annual irrigated crop acreage and include irrigated acreage from organic farms. It is acknowledged that the 2011 maps were subject to more checking and verification than the maps for previous years. According to County staff, specific improvements include refinement to reflect the actual area of crop production rather than the entire parcel, review of pasture information to delete pasture that was not irrigated, identification of walnuts as not irrigated and thus not included), and more accurate mapping of alfalfa; alfalfa acreage has more than doubled since some 800 acres were identified in The crop type classification is consistent with the Evaluation of Paso Robles Groundwater Basin Pumping, Water Year Pumping Update, Todd, 2009) and with the water demand analysis for the 2012 Master Water Report. Crop types are categorized in Table

42 Paso Robles Groundwater Basin Model Update 4-Apr-13 Table 20. Crop Type Classification for San Luis Obispo County Category Crop types Alfalfa alfalfa Nursery flowers, nursery, Christmas trees Pasture clover, mixed pasture, native pasture, misc. grasses, turf farms, turf/sod, Sudan grass Citrus or grapefruit, lemons, oranges, dates, avocados, olives, kiwis, Subtropical jojoba, eucalyptus, pomegranate, subtropical fruits Deciduous apples, apricots, cherries, peaches, nectarines, pears, plums, prunes, figs, pistachios, persimmon, quince Truck or artichokes, asparagus, beans green), corn, Cole crops, Vegetables carrots, celery, lettuce, melon, squash, cucumbers, onion, garlic, peas, potatoes, sweet potatoes, spinach, tomatoes, bush berries, strawberries, peppers, broccoli, cabbage, cauliflower, brussel sprouts, mushroom, mixture, miscellaneous truck Vineyard raisin grapes, table grapes, wine grapes Field Crop forage, forage mix, hay, forage hay, rotational field Grain barley, grain-hay, oats Developed in cooperation with the SLO ACO As in the 2006 Pumping Update, field crops and grains are assumed un-irrigated; these crops were not included in the Master Water Report analysis of irrigated crops. Preparation of the 2012 Master Water Report included evaluation of crop water demands throughout San Luis Obispo County. This evaluation conducted in 2009 and 2010) involved use of the County GIS crop maps and available information on crop water demands, including consultation with University of California Farm Advisors, Resource Conservation District staff, vineyard owners, and agricultural stakeholders ESA, 2010). This evaluation represents the synthesis of recent information on crop water coefficients and accordingly has been adopted herein with refinements focused on vineyards the dominant crop). As described in the preceding section, Applied Water, monthly crop coefficients from the 2012 Master Water Report will be used in this model update with potential adjustments made to consider the following: 1) vineyard canopy development 2) irrigation efficiency 3) regulated deficit irrigation 4) frost protection 5) heat protection, and 36

43 Paso Robles Groundwater Basin Model Update 4-Apr-13 6) leaching requirements. It is noted that the upcoming UC Cooperative Extension study, Quantification of Vineyard Irrigation Amounts, will provide valuable additional information on vineyard irrigation practices in the Estrella and Creston portions of the groundwater basin. This information will be examined when available Municipal Evaluation of municipal groundwater pumping is based on actual records of metered production from wells for Atascadero MWC, City of Paso Robles, Templeton CSD, and San Miguel CSD. The municipal well locations and construction e.g., depth of screens) were provided by each purveyor and groundwater pumping will be allocated respectively to the well locations and vertical zones based on these data. With regard to pumping through time, monthly production data generally are available on a well-by-well basis for the entire study period. For City of Paso Robles wells prior to January 1989, monthly total pumping is available but is not subdivided by individual well. However for this early period, the existing and active wells are known Thunderbird 10, Thunderbird 13, and Butterfield 12) and the monthly production can be allocated based on pumping patterns in subsequent years Small Community Systems Small community water demand is a small portion of the water balance, estimated at less than 600 AFY in Given that community pumping overall represents a relatively small amount, consideration of such variations may not be significant to the model. However, it may be illuminating with regard to the overall variability of rural domestic pumping. The Phase I Study identified 15 small systems, but combined their pumping into the estimate of rural pumping based on population and a water duty factor. Similarly, the 2012 Water Master Plan subsumed the demand of small communities systems into its estimate of rural water demand. The Pumping Update for 2006 identified 13 small systems in San Luis Obispo County, and evaluated pumping amounts using available pumping data to develop a per-person water use rate, which was then applied to other small systems. For this model update, the analysis of small community water system pumping from the Phase I study will be retained as part of the rural domestic pumping for the period 1981 through For the years after 1997, the approach is similar to the Pumping Update for 2006, with the intent to use as much reported pumping data as possible. This recognizes that small community systems have a centralized water system based on one or more wells that should be recognized. Data are available from San Luis 37

44 Paso Robles Groundwater Basin Model Update 4-Apr-13 Obispo County that identify small community systems, provide locations, and in several cases, pumping data. The information on small systems will be used to make sure that parcels served by small systems are distinguished from rural domestic parcels in order to minimize double-counting. The analysis will include the community of Bradley in Monterey County a census-designated community with a population less than 100). Several of the small systems Garden Farms, Shandon, and Green River) have pumping data, generally on a monthly or bi-monthly basis and extending from 1977 to present. This recorded pumping data can be used to represent pumping from rural small community systems over time. Review of the available pumping records indicates that small community pumping amounts tends to be relatively consistent on a year-after-year basis, suggesting that the recorded annual amounts can be applied to other systems, accounting for differences in population or number of connections/dwelling units). For the sake of simplicity, all systems identified as current are assumed to have existed since 1997 with a constant population unless data indicate otherwise). While the year-by-year patterns appear relatively consistent, the available pumping data indicate that seasonal patterns of different systems differ in magnitude. For example, pumping in summer peak months may be three or four times greater than that in winter low months. The differences in magnitude probably reflect the extent of landscaping in the community; more extensive landscaping entails higher summer peaks. The extent of landscaping per residence will be assessed in the three small systems with pumping records. For small systems with pumping data, it is noted that the data represent gross pumping and not net consumption. Accordingly, return flows need to be addressed. For this model update, it is recognized that rural communities rely on local or onsite wastewater treatment and disposal facilities that return a significant portion of the pumped groundwater. Specifically, it can be assumed that 90 percent of inside use is returned via septic or local wastewater systems. Of the outside water use, it can be assumed that 85 percent is lost to evapotranspiration and 15 percent is returned. The relative portions of inside/outside use may approximate 40/60, but local rural residences probably have more outside use. This will be checked by examining the seasonal pumping patterns; winter pumping approximates inside use, while summer pumping also includes outside use Small Commercial Small rural commercial water demand involves a wide variety of establishments and facilities including Atascadero State Hospital, Camp Roberts, rural schools, wineries and rural businesses. The Phase I Study identified 20 small systems and estimated annual water demand using a mix of pumping data and 38

45 Paso Robles Groundwater Basin Model Update 4-Apr-13 estimates. The Pumping Update for 2006 identified 18 small commercial systems and 64 wineries and used a mix of pumping data and estimates for type-specific water demand rates for The 2006 Pumping Update estimated small commercial pumping amounted to 2,324 AF. The 2012 Water Master Plan used the County GIS to define the distribution and number of commercial systems and applied an annual factor of 1.5 AFY per unit. For the model update, the analysis from the Phase I Study will be retained for the years up to For subsequent years, the GIS coverage of active small commercial systems provided by the SLO County will be used to define the distribution and types of commercial systems in unincorporated portions of the study area on an annual basis. Additional wineries not served by public water systems) have been identified through examination of the State Department of Alcohol Beverage Control permit data ABC, 2012). A preliminary evaluation of active ABC licenses indicates that the number of wineries in the Study Area since 2006 has increased significantly. As in the 2006 Pumping Update, pumping data will be used insofar as available e.g., from Atascadero State Hospital) to provide a monthly record from 1978 through For small commercial water systems without pumping records, water use coefficients will be applied. As in the 2006 Pumping Update, commercial water use coefficients are available from research conducted by the Pacific Institute 2003). These coefficients included the following: camp 0.208), school 0.163), institution 0.107) and restaurant 0.229). Annual water demands will be distributed seasonally, accounting for assumed landscaping needs. Gross pumping will be distinguished from net consumption, assuming rural use of onsite-wastewater disposal septic) systems. In the 2006 Pumping Update, winery water use was estimated using an average value of 2.5 gallons per gallon of wine produced. This value is on the low end of winery water demand. While specific wineries have documented relatively low water demands, an acknowledged rule of thumb has been 6 gallons per water per gallon wine Franson, 2008). Pending additional data, a rate between 4 and 6 gallons will be applied to each winery s permitted annual production. It is realized that wineries may not produce as much wine as permitted and this assumption may result in over-estimation of water demand. However, it is also realized that water use at a specific winery may also include landscaping and wine tasting/restaurant functions that are not reflected in the rule of thumb value. Annual water demand will be distributed throughout the months of the year with a seasonal peak in September/October ESA, 2012). For wineries in unincorporated areas, on-site groundwater supply is assumed. Following use, on-site wastewater disposal also is assumed through leachfields or percolation ponds. It is recognized that some wineries have treatment systems and may use process wastewater for irrigation. Such irrigation already is assumed to be based on groundwater pumping, and no data are readily available to discern different 39

46 Paso Robles Groundwater Basin Model Update 4-Apr-13 sources. In addition, the proportion of winery return flows also is variable, with a general estimate of 30 to 40 percent Chrobak, 2013). For the purposes of this model update, a general return rate of 35 percent is assumed Rural Domestic The Phase I Study estimated rural water demand as the product of County estimates of rural dwelling units DU) and a water demand factor of 1.7 AFY per dwelling unit DU); small community system water demand was included. The Pumping Update for 2006 applied the same water factor to dwelling units, with geographic distribution provided by the County GIS. The Pumping Update estimated rural domestic pumping at 10,891 AF in 2006 not including small community water systems). The 2012 MWP also used the County GIS to define the distribution and number of rural DUs and applied a 1.0 AFY/DU factor. For the model update, the analysis from the Phase I Study will be retained for the years up to For subsequent years, the County Land Use ArcGIS layer and associated spreadsheets will be used to define the annual distribution and number of rural DUs in San Luis Obispo County. Monterey County rural population is very small; rural water demand may be estimated from review of aerial photographs or population data. The water demand rate for rural residences is variable; a major factor is the extent of irrigated landscaping. A comprehensive survey of rural residential landscaping and water use is beyond the scope of this model update. Nonetheless, a survey using existing aerial photography) will be conducted in selected rural residential areas to assess landscaping extent and to evaluate the range of water demand rates. As indicated in the discussion of Small Community Water Systems, the extent of landscaping per residence will be sampled in the three small systems with pumping records Garden Farms, Shandon, and Green River). In addition, sampling will be conducted in other areas distributed across the basin and involving a variety of residence/lot sizes. Recommended areas include the Del Salinas Via area northwest of Paso Robles and the Rancho La Loma area near Creston. In each, five residential parcels will be selected, the irrigated landscape area e.g., lawn) will be measured, and the water demand of the landscaping will be estimated. This will provide limited, but real data to evaluate the range of rural residential water demands on a per-dwelling unit basis. As with small rural community pumping, gross pumping will be distinguished from net consumption. It will be assumed that rural residences rely on onsite wastewater treatment and disposal facilities septic tanks) that return a significant portion of the pumped groundwater. 40

47 Paso Robles Groundwater Basin Model Update 4-Apr Total Pumping Total gross groundwater pumping will be tabulated on a subarea and an annual basis for the major categories of agricultural, municipal, small community, small commercial, and rural residential uses Evapotranspiration by Riparian Vegetation Riparian vegetation or phreatophytes) not only use available rainfall and soil moisture, but also pull up and consume groundwater. This groundwater uptake, assumed to occur when rainfall and soil moisture are inadequate, is addressed in this section. This uptake is a relatively small component of the water balance, estimated to average 3,800 AFY for the Paso Robles Basin in the Phase I Study. The Phase I estimate was based on California Department of Forestry and Fire Protection CDFFP) GIS coverage for 1991; this mapping was part of a state-wide project to inventory hardwood rangelands CDFFP, 1994). Riparian vegetation was delineated from LANDSAT imagery and defined within a 375-meter distance from perennial streams as mapped by USGS. The mapping also included inspection of aerial photographs and field checking. For this model update, the availability of more recent riparian woodland mapping was investigated. Currently, the USDA Forest Service is mapping existing vegetation throughout California USDA, 2013). However, the mapping of the Central Coast Calveg Zone 6) is currently incomplete; in fact, the Paso Robles Basin and watershed south of the county line is not yet mapped. Recognizing that vegetation mapping is well beyond the scope of this update, the CDFFP mapping is retained for this model update. However, comparison of the CDFFP and available Calveg mapping in the northernmost portion of the basin indicates that phreatophyte vegetation has expanded in areal extent along the Salinas River. This is likely the result of upstream reservoir releases; however, riparian vegetation in other portions of the watershed also may have increased locally e.g., reflecting urban sources) or decreased. Accordingly, future updates should utilize current maps to reevaluated phreatophyte water uptake. The Phase I Study used this mapping and estimated the phreatophyte groundwater consumption by using an assumed annual water demand 0.8 AF/AC/YR), adjusted annually in response to rainfall. Subsequently, in the Phase II Study, the average groundwater consumption was increased from 3,800 AFY to 7,700 AFY. Assuming that the mapping is accurate, this suggests that the groundwater uptake value was low. For this model update, the phreatophyte consumption of rainfall and soil moisture can be addressed with a monthly soil moisture balance. The plant-water-use coefficient similar to the crop coefficient) is assumed to be 1.0 and applied monthly year-round Stephens, 1996). Any potential deficit in potential ET is assumed to be compensated fully by groundwater uptake. 41

48 Paso Robles Groundwater Basin Model Update 4-Apr-13 Riparian water demand will be estimated monthly for the period of record using the evapotranspiration EVT) package in MODFLOW, which considers the effect of groundwater levels on phreatophyte water consumption Subsurface Outflow Available information indicates that subsurface outflow occurs at the outlet of the basin near San Ardo. In the Phase I Study, outflow was estimated using Darcy s Law at 600 AFY and assumed constant, given the moderating effect of Nacimiento and San Antonio river flows and stability of local hydrographs. This is a reasonable evaluation given the general lack of local groundwater development and information. In the Phase II Study, subsurface outflow was simulated at a higher rate, averaging 1,600 AFY and ranging from 1,300 to 2,100 AFY. In both studies, subsurface outflow is indicated to be a very small portion of total outflow. For this model update, inquiries were made to Monterey County Water Resources Agency for any significant new information e.g., a nearby pumping test) to warrant independent re-evaluation Criollo, 2013). No new data were identified; accordingly, the existing estimates are accepted, understanding that application of the updated model will provide updated estimates of subsurface outflow over time. 42

49 Paso Robles Groundwater Basin Model Update 4-Apr SUMMARY Data obtained from the partnering agencies has been completed with the exception of some additional wastewater flows still to be provided see Table 5). The data has been used to construct the watershed model. The ground water discharge components e.g., agricultural pumping) will be calculated as described and under the assumptions provided. These components will be used as input parameters for the watershed model. Based on the assumptions presented herein, the watershed model will be used to calculate the essential inflow parameters: deep percolation from rainfall, deep percolation from streambed seepage, deep percolation from applied irrigation, and subsurface inflows from the margins of the ground water basin. After review of the data, approach, and assumptions presented in this Technical Memorandum, a technical meeting will be held to discuss any comments by the District and Modeling Subcommittee, and to consider any proposed revisions to the approach to the water balance estimation. 43

50 Paso Robles Groundwater Basin Model Update 4-Apr REFERENCES AQUA TERRA, REVIEW Simulation Plan for Hydrologic Modeling of Calleguas Creek Watershed with the U.S. EPA Hydrologic Simulation Program FORTRAN HSPF). Prepared for Larry Walker Associates, Ventura County Watershed Protection District, and Calleguas Creek Watershed Management Plan. Allen, Richard et al., Crop Evapotranspiration Guidelines for Computing Crop Water Requirements, Food and Agriculture Organization FAO), Atterbury, Tom, Atterbury & Associates, Healdsburg, personal communication, February 19, Battany, Mark, Paso Robles Soil Salinity Survey, Grape Notes, San Luis and Santa Barbara Counties, April Battany, Mark, A Historical Perspective on the April 2011 Frosts: Just Like Old Times, Grape Notes, San Luis and Santa Barbara Counties, September Battany, M., University of California Cooperative Extension Viticulture/Soils Farm Advisor San Luis Obispo County) personal communications, February 4, Bettiga, Larry, University of California Cooperative Extension Viticulture Farm Advisor Monterey County) personal communication, February 5, Beal, Kris, History of Water Conservation Practices & Outreach: Winegrape Industry Initiatives, Presentation to the Paso Robles Groundwater Steering Committee, August Posted on Central Coast Vineyard Team website, Accessed Feb 12, California Department of Forestry and Fire Protection CDFFP), Riparian Vegetation in Hardwood Rangelands, Accessed Feb Carollo et al., San Luis Obispo County Master Water Report, Volumes 1 through III. Prepared for the San Luis Obispo County Flood Control and Water Conservation District. May

51 Paso Robles Groundwater Basin Model Update 4-Apr-13 Chrobak, Bob, Kennedy/Jenks Consultants, San Francisco, personal communication, February 19, Criollo, Germán, Monterey County Water Resources Agency Associate Hydrologist, personal communication, January 15, ESA, San Luis Obispo County Annual Crop-Specific Applied Water Variables, Appendix A to Appendix D of San Luis Obispo County Master Water Report, January 7, ESA, Henry Cornell Winery Draft EIR, Prepared for County of Sonoma Permit and Resource Management Department, August Franson, Paul, Water Use in the Winery, How Wineries Are Conserving, Wine Business Monthly, December Fugro West and Cleath and Associates, Paso Robles Groundwater Basin Study Phase I). Prepared for San Luis Obispo County Public Works Department. Fugro West, ETIC Engineers, and Cleath and Associates, Paso Robles Groundwater Basin Study, Phase II, Numerical Model Development, Calibration, and Application. Prepared for San Luis Obispo County Public Works Department. Monterey County Water Resources Agency MCWRA), Ground Water Extraction Summary Reports, 1995 through See Available Data and Reports, Monterey County Water Resources Agency MCWRA), Ground Water Extraction Summary Report, ort.pdf Peterson, Kevin, Irrigation Specialist, Personal Communication, Cachuma RCD. Prichard, Terry L., Rhonda J. Smith, and Paul S. Verdegaal, no date. Regulated Deficit Irrigation Management for Winegrapes, Accessed Feb 12, Prichard, Terry L., Imposing Water Deficits to Improve Wine Quality and Reduce Costs, no date. Accessed Feb 12,

52 Paso Robles Groundwater Basin Model Update 4-Apr-13 Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Soil Survey Geographic SSURGO) Database for Paso Robles, CA. Available online at 00dbaddea5ea. Richard Nauman Michael Dangermond Charlie Frye Stephens, Daniel B., Vadose Zone Hydrology, Trapp, R., Personal communication via ) between Joseph Kingsbury GEOSCIENCE) and Ryan Trapp San Luis Obispo County Department of Agriculture). Todd Engineers, Evaluation of Paso Robles Groundwater Basin Pumping, Water Year Prepared for the City of Paso Robles and San Luis Obispo County Department of Public Works. U.S. EPA, BASINS Technical Note 6, Estimating Hydrology and Hydraulic Parameters for HSPF. July, EPA-823-R U.S. Environmental Protection Agency, Office of Water, Washington, D.C. USDA Forest Service, Pacific Southwest Region R5) CALVEG Mapping most recent update: ) Accessed Feb Williams, Larry E., Irrigation of Winegrapes in California, Practical Winery & Vineyard Magazine, November-December Yates, Gus, Peer Review of Paso Robles Groundwater Studies, Memorandum to City of Paso Robles, June 29,

53 FIGURES

54 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron Stratford PROJECT LOCATION San Lucas Coalinga Aã KÍ San Ardo Aª Avenal Kettleman City?Ô Pacific Ocean Monterey Co San Luis Obispo Co San Simeon Lockwood Cambria San Antonio Reservoir Nacimiento Reservoir Santa Rosa Creek Harmony Bradley Bradley Sub-Area Lake Nacimiento North Gabilan Sub-Area?h Unsaturated San Miguel South Gabilan Sub-Area Estrella Sub-Area Paso Robles Templeton Atascadero Subbasin Atascadero AÄ?h Creston Sub-Area Unsaturated Parkfield?c Shandon Sub-Area Shandon Fresno Co San Juan Sub-Area Cholame?c Devils Den?ü?h "^$ Kings Co Kern Co Lost Hills Cayucos?v Morro Creek Morro Bay?Ô Los Osos Chorro Creek Santa Margarita Salinas Reservoir San Luis Obispo San Juan Creek EXPLANATION Paso Robles Ground Water Basin Boundary with Sub-basins Source: Fugro, 2002) Watershed Boundary County Boundary Regional Location KÍ AÃ Project Area Pismo Beach Grover Beach Oceano 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 1 GIS_proj/co_slo_paso_robles_model/02_Fig_1_Gen_Project_Loc_4-13.mxd Miles

55 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron HYDROLOGIC SOIL TYPES IN THE PASO ROBLES AREA WATERSHED Stratford Coalinga San Lucas ã A ª A Í K EXPLANATION San Ardo? Ô Lockwood Group A. Soils having a high infiltration rate low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Kettleman City Avenal Fresno Co c? Parkfield ek San Antonio Reservoir Big Sandy Cre Bradley San Luis Obispo Co $ ^ "? ü Monterey Co Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Kings Co Nacimiento Reservoir Devils Den San Miguel Kern Co Lake Nacimiento Cholame ll tre Es Paso Robles Shandon r i ve ar h? San Simeon San ta R Cambria osa C ree k h? Ä A Templeton h? c? Group D. Soils having a very slow infiltration rate high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. Harmony ci Pa Atascadero O fi c cea v? Cayucos n r ro Mo k ee Cr Santa Margarita Cr? Ô Los Osos Salinas Reservoir Ch or ro ee k Morro Bay Source: ESRI, 2012 NRCS SSURGO data table MUAGGATT, field HYDGRPDCD San San Luis Obispo nc Jua re e à A k Í K Grover Beach Oceano 4-Apr-13 NORTH Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. GIS_proj/co_slo_paso_robles_model/02_Fig_2_Soils_4-13.mxd Miles Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary Pismo Beach Lost Hills Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. County Boundary FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 2

56 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT San Lucas Coalinga APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron Aã Stratford PRECIPITATION STATION LOCATIONS KÍ San Ardo Aª Avenal Kettleman City?Ô Pacific Ocean Monterey Co San Luis Obispo Co San Simeon 703 Lockwood #* Cambria San Antonio Reservoir 201 Nacimiento Reservoir #* Harmony #* #* Bradley #* Lake Nacimiento #* Cayucos Tablas Ck?h #* Templeton Gap #* #* #* San Miguel #* #* Paso Robles Templeton #* #* #* Atascadero #* AÄ 711 #*?h 709 Paso Robles #* 211 #* #* Parkfield #* Creston?c #* Shandon?v #* 721 Fresno Co Shandon Cholame #* Kings Co Kern Co ?c?ü Devils Den?h "^$ Lost Hills #* #* #* EXPLANATION Precipitation Station SLOCFCWCD NOAA Western Water Group Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary County Boundary Morro Bay?Ô Los Osos 95 #* #* #* #* Santa Margarita San Luis Obispo #* 94 Salinas Reservoir #* 186 KÍ AÃ GIS_proj/co_slo_paso_robles_model/02_Fig_3_Precip_stn_locs_4-13.mxd Pismo Beach Grover Beach Oceano 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 3 Miles

57 Paso Robles Groundwater Basin Model Update 40 Annual Precipitation Oak Shores Station #201) ) Annual Precipitation, inches Average Annual Precipitation =14.7 in./yr Source: San Luis Obispo County Figure 4 4-Apr-13 Todd Engineers

58 Paso Robles Groundwater Basin Model Update 40 Annual Precipitation NOAA Station ) Annual Precipitation, inches Average Annual Precipitation = 15.1 in./yr Source: National Climatic Data Center NOAA) database Figure 5 4-Apr-13 Todd Engineers

59 Paso Robles Groundwater Basin Model Update 40 Annual Precipitation NOAA Station ) Annual Precipitation, inches Average Annual Precipitation =9.8 in./yr Source: National Climatic Data Center NOAA) database Figure 6 4-Apr-13 Todd Engineers

60 Paso Robles Groundwater Basin Model Update 60 Annual Precipitation NOAA Station ) Annual Precipitation, inches Average Annual Precipitation = 32.5 in./yr Source: National Climatic Data Center NOAA) database Figure 7 4-Apr-13 Todd Engineers

61 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE San Lucas Coalinga Huron Aã Stratford EVAPOTRANSPIRATION STATION LOCATIONS KÍ San Ardo Aª Avenal Kettleman City?Ô Pacific Ocean Monterey Co San Luis Obispo Co San Simeon Lockwood Cambria San Antonio Reservoir Nacimiento Reservoir Harmony ) Bradley Lake Nacimiento Tablas Ck Templeton Gap?h ) San Miguel ) Paso Robles Templeton AÄ Atascadero Paso Robles?h ) Parkfield?c Creston Shandon ) Fresno Co Shandon Cholame?c?ü Devils Den?h "^$ Kings Co Kern Co Lost Hills ) EXPLANATION Evapotranspiration Station Source: Western Water Group, 2012) Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary County Boundary Cayucos?v Morro Bay?Ô Los Osos Santa Margarita San Luis Obispo Salinas Reservoir KÍ AÃ GIS_proj/co_slo_paso_robles_model/02_Fig_8_ET_stn_locs_4-13.mxd Pismo Beach Grover Beach Oceano 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 8 Miles

62 Paso Robles Groundwater Basin Model Update Historical Daily) Evapotranspiration Paso Robles Station ) 1.0 Evapotranspiration,in Jan-05 Jul-05 Jan-06 Source: Western Weather Group Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Dec-08 Jul-09 Dec-09 Jul-10 Dec-10 Jul-11 Dec-11 Jun-12 Dec-12 Figure 9 4-Apr-13 Todd Engineers

63 Paso Robles Groundwater Basin Model Update Historical Daily) Evapotranspiration Tablas Creek Station ) 1.0 Evapotranspiration,in Jan-05 Jul-05 Jan-06 Source: Western Weather Group Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Dec-08 Jul-09 Dec-09 Jul-10 Dec-10 Jul-11 Dec-11 Jun-12 Dec-12 Figure 10 4-Apr-13 Todd Engineers

64 Paso Robles Groundwater Basin Model Update Historical Daily) Evapotranspiration Shandon Station ) 1.0 Evapotranspiration,in Jan-05 Jul-05 Jan-06 Source: Western Weather Group Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Dec-08 Jul-09 Dec-09 Jul-10 Dec-10 Jul-11 Dec-11 Jun-12 Dec-12 Figure 11 4-Apr-13 Todd Engineers

65 Paso Robles Groundwater Basin Model Update 1.0 Historical Daily) Evapotranspiration Templeton Gap Station ) Evapotranspiration,in Jan-05 Jul-05 Jan-06 Source: Western Weather Group Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Dec-08 Jul-09 Dec-09 Jul-10 Dec-10 Jul-11 Dec-11 Jun-12 Dec-12 Figure 12 4-Apr-13 Todd Engineers

66 Paso Robles Groundwater Basin Model Update 1.0 Historical Daily) Evapotranspiration Creston Station ) Evapotranspiration,in Jan-05 Jul-05 Jan-06 Source: Western Weather Group Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Dec-08 Jul-09 Dec-09 Jul-10 Dec-10 Jul-11 Dec-11 Jun-12 Dec-12 Figure 13 4-Apr-13 Todd Engineers

67 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT?Ô Pacific Ocean Monterey Co San Luis Obispo Co San Simeon Lockwood Cambria San Lucas Harmony KÍ San Antonio Reservoir Nacimiento Reservoir Santa Rosa Creek San Ardo Bradley Lake Nacimiento Cayucos Morro Bay?h Morro Creek?Ô Big Sandy Creek Paso Robles Santa Margarita Creek near Santa Margarita San Miguel Templeton KÍ Atascadero Salinas River below Salinas Dam near Pozo San Luis Obispo AÃ AÄ ?h Aª Hog Canyon Estrella River Parkfield?c Salinas Reservoir?v Coalinga Shandon Fresno Co Cholame Yerba Buena Creek in Santa Margarita APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron Aã Avenal?c?ü Kettleman City Devils Den?h "^$ Kings Co Kern Co Stratford Cholame Creek at Palo Prieta Bitterwater Rd) near Cholame San Juan Creek Lost Hills STREAM GAGING LOCATIONS EXPLANATION USGS Gaging Station SLOFC&WCD Gaging Station Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary County Boundary Pismo Beach Grover Beach Oceano 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 14 GIS_proj/co_slo_paso_robles_model/02_Fig_14_stream_gages_4-13.mxd Miles

68 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Yerba Buena Creek in Santa Margarita ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 May-53 Source: USGS NWIS downloaded Nov-11) Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 15 4-Apr-13 Todd Engineers

69 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Santa Margarita Creek near Santa Margarita ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 16 4-Apr-13 Todd Engineers

70 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Salinas River below Salinas Dam near Pozo ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 17 4-Apr-13 Todd Engineers

71 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Cholame Creek at Palo Prieta Bitterwater Rd) near Cholame ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 18 4-Apr-13 Todd Engineers

72 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Salinas River near Bradley ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 19 4-Apr-13 Todd Engineers

73 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Nacimiento River below Nacimiento Dam near Bradley ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 20 4-Apr-13 Todd Engineers

74 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Nacimiento River below Sapaque Creek near Bryson ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 21 4-Apr-13 Todd Engineers

75 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Estrella River near Estrella ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 22 4-Apr-13 Todd Engineers

76 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Salinas River above Paso Robles ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 23 4-Apr-13 Todd Engineers

77 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Santa Rita Creek near Templeton ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 24 4-Apr-13 Todd Engineers

78 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Salsipuedes Creek near Pozo ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 25 4-Apr-13 Todd Engineers

79 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Toro Creek near Pozo ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 26 4-Apr-13 Todd Engineers

80 Paso Robles Groundwater Basin Model Update 100,000.0 Historical Daily) Streamflow Salinas River near Pozo ) ) Streamflow, cfs 10, , Jan-39 May-41 Oct-43 Mar-46 Aug-48 Dec-50 Source: USGS NWIS downloaded Nov-11) May-53 Oct-55 Mar-58 Aug-60 Dec-62 May-65 Oct-67 Mar-70 Jul-72 Dec-74 May-77 Oct-79 Mar-82 Jul-84 Dec-86 May-89 Oct-91 Mar-94 Jul-96 Dec-98 May-01 Oct-03 Feb-06 Jul-08 Dec-10 Figure 27 4-Apr-13 Todd Engineers

81 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT San Lucas Coalinga APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron Aã Stratford WASTEWATER TREATMENT PLANT LOCATIONS KÍ San Ardo Aª Avenal Kettleman City?Ô Monterey Co Lockwood San Antonio Reservoir Bradley Big Sandy Creek Parkfield Fresno Co?c?ü "^$ #* EXPLANATION Wastewater Treament Plant Location Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) San Luis Obispo Co Nacimiento Reservoir Lake Nacimiento #* San Miguel CSD WWTP San Miguel Cholame Devils Den Kings Co Kern Co Watershed Boundary County Boundary Pacific Ocean San Simeon Cambria Harmony City of Paso Robles WWTP Santa Rosa Creek Cayucos Morro Creek Morro Bay?h?Ô Los Osos #* Paso Robles Templeton #* #* Atascadero AÄ?h Templeton CSD WWTP Chorro Creek Santa Margarita Estrella River?c City of Atascadero WWTP Salinas Reservoir?v Shandon?h Lost Hills San Luis Obispo San Juan Creek KÍ AÃ GIS_proj/co_slo_paso_robles_model/02_Fig_28_wastewater_TP_locs_4-13.mxd Pismo Beach Grover Beach Oceano 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 28 Miles

82 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT R80 KÍ R88 Aª APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Aã TRIBUTARY SUB-WATERSHED OF THE PASO ROBLES AREA WATERSHED?Ô R75 Monterey Co San Luis Obispo Co R76 SanAntonio81 San Antonio Reservoir Nacimiento77 R85 Nacimiento Reservoir R91 R90 R87 R86 R84 R83 R82 R78 R55 R15 R89 R73 Fresno Co R71 R79 R42 R72 R69 R74 R68 R67 R66 R65 R64 R59?h R58 R70 R14 R17 R16 R41 R40 R18 R39 R19 R37 R32 R34 R25 R36 R38 R31 R24 R35 R21 R20 R30 R22 R26 R12 R43?h R23 R33 R63 R27 AÄ?c R13 R11 R10 R62 R9 R8 Kings Co Kern Co?c?ü?h "^$ various colors) EXPLANATION Watershed Boundary Sub-Watershed Boundary and Designation See Table 6) Stream Reach Segment Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) County Boundary Pacific Ocean R56 R57 R54 R61 R29?v R28 R7 R4 R6 R2 R53 R60 R5?Ô R52 R51 R50 R49 SalinasRed48 R46 R3 Salinas Reservoir R45 R44 R47 KÍ AÃ R1 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 29 GIS_proj/co_slo_paso_robles_model/02_Fig_29_model_segmentation_4-13.mxd Miles

83 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Aª Aã 1985 LAND USE CONDITIONS IN THE PASO ROBLES AREA WATERSHED KÍ?Ô San Antonio Reservoir Fresno Co?c EXPLANATION 1985 Land Use Classification Source: Fugro, 2005) Monterey Co San Luis Obispo Co Nacimiento Reservoir?ü "^$ Kings Co Kern Co Agriculture / Park / Golf Course Commercial / Industrial / PublicFacility Low Density Residential?h Open Space / Dry Agriculture / Water Body Pacific Ocean?h AÄ?c?h Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary County Boundary?v?Ô Salinas Reservoir KÍ AÃ 4-Apr-13 Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. N O R T H Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 30a GIS_proj/co_slo_paso_robles_model/02_Fig_30a_1985_land_use_4-13.mxd

84 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Kettleman City Avenal Lockwood C re ek Big S and y Fresno Co San Antonio Reservoir 1985 IRRIGATED AGRICULTURAL TYPES IN THE PASO ROBLES AREA WATERSHED c? Parkfield Bradley EXPLANATION? ü Monterey Co San Luis Obispo Co Nacimiento Reservoir 1985 Land Use Irrigated Agricultural Types Source: Fugro, 2005) Kings Co Alfalfa Kern Co Devils Den San Miguel Deciduous Pasture Lake Nacimiento Truck / Vegetable Cholame Vineyard a rell Est er Ri v h? Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Shandon Paso Robles h? Santa Rosa Creek Ä A Cambria h? Watershed Boundary County Boundary c? Templeton Harmony Atascadero San Juan Cre v? Cayucos ek Pacific Ocean ek Cre o r r Mo Santa Margarita Cr ee k Morro Bay Ch o rro? Ô Salinas Reservoir 4-Apr-13 NORTH Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. GIS_proj/co_slo_paso_robles_model/02_Fig_30b_1985_Ag_areas_4-13.mxd Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 30b

85 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Aª Aã 1997 LAND USE CONDITIONS IN THE PASO ROBLES AREA WATERSHED KÍ?Ô Monterey Co San Luis Obispo Co San Antonio Reservoir Nacimiento Reservoir Fresno Co?c?ü "^$ Kings Co Kern Co EXPLANATION 1997 Land Use Classification Source: DWR 1997 Monterey and 1996 San Luis Obispo.) Agriculture / Park / Golf Course Commercial / Industrial / PublicFacility Low Density Residential?h Open Space / Dry Agriculture / Water Body?h AÄ?c?h Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Pacific Ocean Watershed Boundary?v County Boundary?Ô Salinas Reservoir KÍ AÃ 4-Apr-13 Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. N O R T H Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 31a GIS_proj/co_slo_paso_robles_model/02_Fig_31a_1997_land_use_4-13.mxd

86 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Kettleman City Avenal Lockwood C re ek Big S and y Fresno Co San Antonio Reservoir 1997 IRRIGATED AGRICULTURAL TYPES IN THE PASO ROBLES AREA WATERSHED c? Parkfield Bradley EXPLANATION? ü Monterey Co San Luis Obispo Co Nacimiento Reservoir 1997 Land Use Irrigated Agricultural Types Source: DWR 1997 Monterey and 1996 San Luis Obispo.) Kings Co Alfalfa Kern Co Devils Den San Miguel Deciduous Nursery Lake Nacimiento Cholame Pasture Truck a rell Est er Ri v h? Vineyard Shandon Paso Robles Sa n San ta R osa Cambria Cre e Ä A k h? J ua nc h? ree k Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary c? County Boundary Templeton Harmony Atascadero v? Cayucos Pacific Ocean ek Cre o r r Mo Santa Margarita Cr ee k Morro Bay Ch o rro? Ô Salinas Reservoir 4-Apr-13 NORTH Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. GIS_proj/co_slo_paso_robles_model/02_Fig_31b_1997_Ag_areas_4-13.mxd Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 31b

87 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Aª Aã 2011 LAND USE CONDITIONS IN THE PASO ROBLES AREA WATERSHED KÍ?Ô Monterey Co San Luis Obispo Co San Antonio Reservoir Nacimiento Reservoir Fresno Co?c?ü "^$ Kings Co Kern Co EXPLANATION 2011 Land Use Classification Source: SLOCFCWCD, 2012) Agriculture / Park / Golf Course Commercial / Industrial / PublicFacility Low Density Residential Medium Density Residential Pacific Ocean?h High Density Residential?h AÄ?c?h Open Space / Dry Agriculture / Water Body Paso Robles Ground Water Basin Boundary Source: Fugro, 2002)?v Watershed Boundary County Boundary?Ô Salinas Reservoir KÍ AÃ 4-Apr-13 Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. N O R T H Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 32a GIS_proj/co_slo_paso_robles_model/02_Fig_32a_2011_land_use_4-13.mxd

88 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Kettleman City Avenal Lockwood C re ek Big S and y Fresno Co San Antonio Reservoir 2011 IRRIGATED AGRICULTURAL TYPES IN THE PASO ROBLES AREA WATERSHED c? Parkfield Bradley EXPLANATION? ü Monterey Co San Luis Obispo Co Nacimiento Reservoir 2011 Land Use Irrigated Agricultural Types Source: SLOCFCWCD, 2012) Kings Co Alfalfa Kern Co Devils Den San Miguel Deciduous Nursery Lake Nacimiento Pasture Cholame Truck Vineyard a rell Est er Ri v h? Shandon Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Paso Robles Sa n San ta R osa Cambria Cre e Ä A k h? J ua nc h? ree k c? Watershed Boundary County Boundary Templeton Harmony Atascadero v? Cayucos Pacific Ocean ek Cre o r r Mo Santa Margarita Cr ee k Morro Bay Ch o rro? Ô Salinas Reservoir 4-Apr-13 NORTH Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet. 2013, All rights reserved. GIS_proj/co_slo_paso_robles_model/02_Fig_32b_2011_Ag_areas_2-13.mxd Miles FIRST REVISION P.O. Box 220, Claremont, CA Tel: 909) Fax: 909) Figure 32b

89 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE PRISM PRECIPITATION ADJUSTMENT FACTORS Fresno Co #* EXPLANATION Precipitation Station 42 Monterey Co San Luis Obispo Co #* #* 0.94 #* Kings Co Kern Co 6 Colors of Sub-Watersheds Represent Similar PRISM Precipitation ) Within Each Sub-Watershed As The Respective Precipitation Station Shown Below Station No. 201 Station No Station No Station No Watershed Boundary Pacific Ocean #* Sub-Watershed Boundary and Precipitation Adjustment Factor See Table 15) PRISM Precipitation, in. County Boundary Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 33 GIS_proj/co_slo_paso_robles_model/02_Fig_33_precip_adjust_factors_4-13.mxd Miles

90 7.5 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE ISOHYETAL PRECIPITATION ADJUSTMENT FACTORS Monterey Co San Luis Obispo Co #* #* #* Fresno Co Kings Co Kern Co 6.5 #* EXPLANATION Precipitation Station Colors of Sub-Watersheds Represent Similar Long Term Average Precipitation ) Within Each Sub-Watershed As The Respective Precipitation Station Shown Below Station No. 201 Station No Station No Station No Watershed Boundary Pacific Ocean Sub-Watershed Boundary and Precipitation Adjustment Factor See Table 15) Isohyetal Precipitation, in #* County Boundary Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 34 GIS_proj/co_slo_paso_robles_model/02_Fig_34_isohyetal_adjust_factors_4-13.mxd Miles

91 SAN LUIS OBISPO COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT 1 12 San Lucas KÍ San Ardo Aª Coalinga APPROACH AND METHODOLOGY FOR WATER BALANCE ESTIMATION PASO ROBLES GROUNDWATER BASIN MODEL UPDATE Huron Aã Avenal Kettleman City Stratford REFERENCE EVAPOTRANSPIRATION ETo) ZONES?Ô Pacific Ocean Monterey Co San Luis Obispo Co 1 San Simeon Lockwood Cambria San Antonio Reservoir Nacimiento Reservoir Santa Rosa Creek Harmony 6 Bradley Lake Nacimiento Cayucos Morro Creek Morro Bay?h?Ô Los Osos 1 Big Sandy Creek San Miguel Paso Robles Templeton Chorro Creek KÍ 16 Atascadero Santa Margarita San Luis Obispo AÃ AÄ 3 Pismo Beach Grover Beach Oceano?h Estrella River 10 Parkfield?c Salinas Reservoir?v Shandon Fresno Co Cholame San Juan Creek?c?ü Devils Den?h 16 "^$ Kings Co Kern Co 15 Lost Hills EXPLANATION Evapotranspiration ETo) Zones Source: CIMIS, 2013) Coastal Plains Heavy Fog Belt Coastal Valleys and Plains and North Coast Mountains Upland Central Coast and Los Angeles Basin North Central Plateau & Central Coast Range East Side Sacramento- San Joaquin Valley Northern & Southern San Joaquin Valley Westside San Joaquin Valley & Mountains East & West of Imperial Valley Paso Robles Ground Water Basin Boundary Source: Fugro, 2002) Watershed Boundary County Boundary 4-Apr-13 N O R T H Prepared by: DWB. Map Projection: UTM 1927, Zone 10. feet P.O. Box 220, Claremont, CA FIRST REVISION Tel: 909) Fax: 909) , All rights reserved. Figure 35 GIS_proj/co_slo_paso_robles_model/02_Fig_35_ET_zones_4-13.mxd Miles

92 TABLES

93 Paso Robles Groundwater Basin Model Update Data Inventory Type Subtype Description of Data FTP Folder Source Climate Precipitation Rain gage data 1_Climate/Precip/Rain Gage Data CDEC, NOAA, CIMIS, SLO County Climate Precipitation GIS - Isohyetal precipitation map from PRISM OSU) 1_Climate/Precip/PRISM_Isohyet_Raster PRISM OSU) Climate ET and/or pan evaporation CIMIS ET data 1_Climate_ET_CIMIS CIMIS Climate ET and/or pan evaporation Wine Country Alliance ET data 1_Climate_ET_Western Weather Group SLO County Geology Geology and Faults GIS - Geology and fault coverages 2_Geology_Faults SLO County Geology Geology Faults Well completion reports 2004 fault investigation report for Rancho Santa Ysabel, Paso Robles / geologic hydrogeologic investigations Driller's logs, pumping test data, geophysical surveys focused on area near Rinconada Fault separating Atascadero subbasin and Creston subarea 2_Geology_Faults 2_Geology_WCRs SLO County Groundwater Groundwater levels Groundwater levels from SLO County monitoring program 3_Groundwater/Water Levels SLO County Groundwater Pumping / demand Municipal pumping by individual well) for City of Paso Robles, Atascadero MWC, Templeton CSD system total), San Miguel CSD monthly); including well screen information and locations 3_Groundwater/Municipal Pumping Groundwater Pumping / demand Small community water systems pumping 3_Groundwater/Small Community Pumping SLO County Groundwater Pumping / demand Commercial water systems demand 3_Groundwater/Commercial Pumping SLO County Groundwater Pumping / demand Agricultural crop water demand estimates Master Water Plan App. D) 3_Groundwater/Agricultural Pumping DWR Various SLO County GW Model GW Model Calibrated MODFLOW-2000 groundwater flow model 4_Original_Model_Files SLO County Land Use Land Use Land Use Land Use Land Use Agriculture Land Use / Zoning General General General GIS - Historical agricultural crop maps 1996 through 2011) for SLO County; 2012 coverage of irrigated crops for SLO County; 2012 crop coverage for Monterey County GIS - Assessor's parcel coverage - SLO County and southern Monterey County Unincorporated areas - planning and assessor's on-the-ground) land use/zoning data fields Incorporated cities - planning and assessor's on-the-ground) land use/zoning data fields; boundaries for future demand planning and UWMP/ag updates GIS - General Plan land use / zoning coverage and associated data fields 5_Land Use/Agriculture/SLO County and Monterey County 5_Land Use/Zoning/on_the_ground/ Parcels 5_Land Use/Zoning/on_the_ground/zoning 5_Land Use/Zoning/on_the_ground/cities 5_Land Use/Zoning/General Plan SLO & Monterey Counties; USDA NRCS ParcelQuest SLO County SLO County SLO County Land Use Land Use GIS - Land use coverage and associated data fields 5_Land Use/Zoning/General Plan City of Atascadero Table 1 4-Apr-13 Page 1 of 2 Todd Engineers

94 Paso Robles Groundwater Basin Model Update Data Inventory Type Subtype Description of Data FTP Folder Source Land Use Land Use GIS - Land use coverage and associated data fields 5_Land Use/Zoning/General Plan City of Paso Robles Soil Soil hydrology GIS - USDA NRCS soil type and hydrologic properties 6_Soil/USDA NRCS USDA NRCS Surface Water Stream features CALWATER watershed boundaries 7_Surface Water/GIS/Watershed boundaries CALWATER Surface Water Stream features Stream channel location, geometry USGS National Hydrography Dataset); 7_Surface Water/GIS/National Hydrography Dataset Surface Water Stream discharge USGS stations - daily stream discharge 7_Surface Water/Discharge/USGS USGS NWIS Surface Water Surface Water Surface Water Surface Water Surface water Stream discharge Reservoir spills and releases Reservoir spills and releases Reservoir spills and releases Recharge / percolation ponds County Flood Control and Water Conservation District-operated stations - locations and daily stream discharge , if available) San Antonio and Nacimiento reservoirs - daily operational data ) Salinas Reservoir Santa Margarita Lake) - daily operational data ) Nacimiento Water Project daily flow deliveries to turnouts of interest Paso Robles, Atascadero MWC, Templeton CSD) ) Locations and recharge volumes for two percolation ponds operated by Templeton CSD and Atascadero MWC 7_Surface Water/Discharge/SLO County FC&WCD 7_Surface Water/Reservoirs/San Antonio and Nacimiento 7_Surface Water/Reservoirs/Salinas Reservoir_SM Lake 7_Surface Water/Reservoirs/Nacimiento WP 7_Surface Water/Perc Ponds USGS SLO County MCWRA SLO County SLO County TCSD, AMWC Surface Water Stream diversions SWRCB reports of well pumping of stream underflow 7_Surface Water/Stream Diversions SLO County Topography / Ground Cover Topography / Ground Cover Wastewater Aerial Photographs Vegetation coverage WWTP discharges USGS 2011 orthophotographs of study area - 1-foot and 6-inch resolution / 1999 aerials from SLO County GIS - detailed vegetation coverage, including riparian California Department of Forestry and Fire Protection, 1994) and CALVEG mapping mapping not complete) WWTP discharges by City of Paso Robles, City of Atascadero, Atascadero State Hospital, Templeton CSD, San Miguel CSD monthly) 8_Aerials_Ground Cover/Aerials/2011 and _Aerials_Ground Cover/RiparianMapping 9_Wastewater/Municipal discharges USGS CDFFP Various Table 1 4-Apr-13 Page 2 of 2 Todd Engineers

95 Paso Robles Groundwter Basin Model Update Table 6 Paso Robles Groundwater Basin Watershed Model Segmentation Sub-Watershed Drainage Area Stream Length [ft] R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R Apr-13 Page 1 of 3 Todd Engineers

96 Paso Robles Groundwter Basin Model Update Table 6 Paso Robles Groundwater Basin Watershed Model Segmentation Sub-Watershed Drainage Area Stream Length [ft] R R R R R R R R R R R R SalinasRes R R R R R R R R R R R R R R R R R R R R R R Apr-13 Page 2 of 3 Todd Engineers

97 Paso Robles Groundwter Basin Model Update Table 6 Paso Robles Groundwater Basin Watershed Model Segmentation Sub-Watershed Drainage Area Stream Length [ft] R R R R R R Nacimiento R R R SanAntonio R R R R R R R R R R Note: Refer to Figure 29 for locations of sub-watersheds 4-Apr-13 Page 3 of 3 Todd Engineers

98 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1985) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential R , ,836 R , ,208 R , ,013 R , ,046 R ,069 1, , ,781 R , ,952 R , ,384 R , ,740 R , ,235 R , ,421 R , , ,404 R , ,284 R , ,812 R , ,783 R , ,367 R , ,171 R , ,406 R , ,000 R , ,601 R , ,599 R , ,870 R , ,370 R , , ,004 R , ,094 R , ,716 R R , ,740 R28 1, , , ,006 Medium Density Residential High Density Residential Total Area Table 7 4-Apr-13 Page 1 of 4 Todd Engineers

99 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1985) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R , ,744 R , , ,532 R , ,860 R , ,114 R , ,017 R , ,858 R , ,099 R , ,052 R , ,307 R , ,031 R , ,597 R , ,403 R , ,787 R , ,535 R43 1, ,031 2, , ,052 R , ,993 R , ,438 R , ,120 R , ,902 SalinasRes , ,305 R , ,834 R , ,686 R , ,781 R , ,460 R , ,758 R , ,850 R , ,806 R , ,948 Total Area Table 7 4-Apr-13 Page 2 of 4 Todd Engineers

100 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1985) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R , , , ,353 R , ,978 1, ,126 R , ,377 R , ,258 R , ,144 R62 1, , , , ,764 R , ,891 R , ,346 R , , ,078 R , ,781 R , ,296 R , ,521 R , ,027 R , ,102 R , ,081 R , ,110 R , ,373 R , ,428 R , ,880 R , ,974 Nacimiento , ,240 R , ,059 R , ,798 R , ,326 SanAntonio , ,453 R , ,595 R , ,122 R , ,495 Total Area Table 7 4-Apr-13 Page 3 of 4 Todd Engineers

101 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1985) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R , ,541 R , ,205 R ,053 R , ,717 R , ,373 R ,674 1, ,062 R , ,619 TOTAL 10, , ,032 24,632 5,447 1,629,337 3, ,662,677 Total Area Table 7 4-Apr-13 Page 4 of 4 Todd Engineers

102 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1997) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential R , ,836 R , ,208 R , ,013 R , ,046 R , ,781 R , ,952 R , ,384 R , ,740 R , ,235 R , ,421 R ,052 1, , ,404 R , ,284 R , ,812 R , ,783 R , , ,330 R , ,171 R , ,392 R , ,976 R , ,601 R , ,103 R , ,870 R , ,370 R , ,004 R , ,094 R , ,716 R R , ,740 R , ,006 Medium Density Residential High Density Residential Total Area Table 8 4-Apr-13 Page 1 of 4 Todd Engineers

103 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1997) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R , ,744 R , ,532 R , ,860 R , ,114 R , ,017 R , ,858 R , ,099 R , ,052 R , ,307 R , ,031 R , ,597 R , ,403 R , ,778 R , ,535 R43 1, ,062 3, , ,052 R , ,993 R , ,438 R , ,120 R , ,902 SalinasRes , ,305 R , ,834 R , ,686 R , ,781 R , ,460 R , ,758 R ,505 1, ,850 R , ,806 R , ,948 Total Area Table 8 4-Apr-13 Page 2 of 4 Todd Engineers

104 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1997) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R ,205 5, ,353 R ,080 1, ,366 4, ,130 R , ,377 R , ,258 R , ,144 R , , , ,762 R ,040 1, , ,891 R , ,346 R ,112 2, ,725 1, ,078 R , ,781 R , ,296 R , ,521 R , ,027 R , ,102 R , ,081 R , ,110 R , ,345 R , ,428 R , ,880 R , ,974 Nacimiento ,633 1, ,240 R , ,059 R , ,798 R , , , ,326 SanAntonio , ,453 R , ,595 R , ,122 R , ,495 Total Area Table 8 4-Apr-13 Page 3 of 4 Todd Engineers

105 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 1997) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R ,355 1, , ,541 R , ,205 R ,053 R , ,717 R , ,373 R ,640 1, ,062 R , ,619 TOTAL 4, ,387 1,761 13,706 31,175 2,995 1,607,438 19, ,661,069 Total Area Table 8 4-Apr-13 Page 4 of 4 Todd Engineers

106 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 2011) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential R ,688 1, ,837 R , ,208 R , ,013 R , ,047 R ,114 1, ,340 1, ,781 R , ,952 R , ,384 R , ,740 R , ,235 R ,946 2, ,421 R ,274 1, ,556 1, ,404 R , ,284 R ,815 R , ,783 R , ,367 R , ,171 R , ,406 R , ,000 R , ,601 R , ,599 R ,317 1, ,870 R , ,370 R , , ,004 R , ,094 R , ,716 R R , ,740 R , ,185 2, ,006 Medium Density Residential High Density Residential Total Area Table 9 4-Apr-13 Page 1 of 4 Todd Engineers

107 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 2011) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R ,778 2, ,745 R ,083 2, ,784 2, ,532 R , ,860 R ,623 1, ,114 R ,017 R , ,858 R , ,099 R , ,053 R , ,307 R , ,031 R , ,597 R ,442 1, ,403 R ,543 1, ,778 R , ,535 R ,695 7, ,095 4, ,027 R , ,998 R , ,438 R , ,120 R , ,902 SalinasRes , ,305 R ,904 5, ,834 R , ,683 R , ,781 R ,144 1, ,460 R ,879 1, ,758 R ,112 4, ,719 R ,044 1, ,376 11, ,823 R ,632 6, ,951 Total Area Table 9 4-Apr-13 Page 2 of 4 Todd Engineers

108 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 2011) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R ,245 17, ,315 R ,865 3,969 1,045 16,852 14,364 1, ,977 R ,159 R ,001 4, ,258 R ,440 4, ,144 R ,008 6, ,490 17, ,636 R ,392 1, ,186 2, ,368 R ,129 R ,765 3,284 1,066 4,176 6, ,834 R ,230 4, ,781 R ,289 R , ,522 R ,807 1, ,027 R , ,102 R , ,081 R , ,111 R , ,597 R ,158 1, ,428 R , ,880 R , ,974 Nacimiento ,236 1, ,168 1, ,243 R , ,059 R , ,798 R , ,326 SanAntonio , ,453 R , ,595 R , ,122 R , ,495 Total Area Table 9 4-Apr-13 Page 3 of 4 Todd Engineers

109 Paso Robles Groundwater Basin Model Update Sub-Watershed Land Use Summary 2011) Sub-Watershed Agriculture/Parks/Golf Course Alfalfa Deciduous Nursery Pasture Truck Vineyard Total Commercial/ Industrial/ Public Facility Open Space/ Dry Agriculture/ Water Body Low Density Residential Medium Density Residential High Density Residential R ,725 1, , ,550 R , ,205 R ,053 R , ,717 R , ,373 R , ,062 R , ,619 TOTAL 2, ,279 2,332 38,864 45,749 5,375 1,462, ,537 2,481 1,074 1,662,254 Total Area Table 9 4-Apr-13 Page 4 of 4 Todd Engineers

110 Paso Robles Groundwater Basin Model Update Sub-Watershed Soil Summary Sub- Watershed Group A Soils Group B Soils Group C Soils Group D Soils [%] [%] [%] [%] R % 28, % 15, % 53, % 96,836 R % 11, % % 3, % 15,208 R % 6, % % % 7,013 R % 6, % % 2, % 9,046 R % 19, % 3, % % 23,781 R % 14, % % 2, % 17,952 R % 9, % 0 0.0% 5 0.1% 9,384 R % 6, % 0 0.0% 1, % 7,740 R % 4, % % % 5,235 R % 20, % 4, % 3, % 28,421 R % 9, % 3, % 5, % 18,404 R % % 1, % 2, % 4,284 R % 1, % % % 1,812 R % 3, % 6, % 7, % 17,783 R % 2, % 5, % 18, % 26,367 R % % 7, % 1, % 10,171 R % 2, % 10, % 17, % 31,406 R % 4, % 7, % 10, % 23,000 R % 2, % 7, % 2, % 12,601 R % 4, % 10, % 5, % 20,599 R % 2, % 2, % 4, % 9,870 Total Area R % % % % 1,370 R % 1, % % % 3,004 R % % 4, % 1, % 6,094 R % % 2, % % 2,716 R % % % % 398 R % 2, % 1, % % 3,740 R % 27, % 3, % 3, % 34,006 Table 15 4-Apr-13 Page 1 of 4 Todd Engineers

111 Paso Robles Groundwater Basin Model Update Sub-Watershed Soil Summary Sub- Watershed Group A Soils Group B Soils Group C Soils Group D Soils [%] [%] [%] [%] Total Area R % 17, % 5, % 6, % 30,744 R % 8, % 7, % 2, % 18,532 R % % 1, % % 2,860 R % % 12, % % 14,114 R % % % % 1,017 R % % 6, % % 7,858 R % % 1, % % 2,099 R % % 1, % % 2,052 R % % 5, % % 7,307 R % % % % 1,031 R % % 8, % % 9,597 R % 1, % 12, % % 14,403 R % 1, % 12, % 1, % 14,778 R % % 8, % 1, % 11,535 R % 9, % 9, % 2, % 22,052 R % 7, % 13, % 22, % 44,993 R % % 1, % 3, % 5,438 R % 2, % % 2, % 6,120 R % % 1, % 1, % 2,902 SalinasRes % % 2, % 8, % 12,305 R % 4, % 23, % 4, % 32,834 R % 3, % 2, % 2, % 8,686 R % 1, % % % 2,781 R % % % 5, % 6,460 R % 2, % % 2, % 5,758 R % 3, % 5, % 1, % 10,850 R % 5, % 13, % 7, % 26,806 Table 15 4-Apr-13 Page 2 of 4 Todd Engineers

112 Paso Robles Groundwater Basin Model Update Sub-Watershed Soil Summary Sub- Watershed Group A Soils Group B Soils Group C Soils Group D Soils [%] [%] [%] [%] Total Area R % 4, % 2, % 4, % 11,948 R % 10, % 7, % 15, % 34,353 R % 11, % 20, % 5, % 38,130 R % 1, % 1, % % 3,377 R % 4, % 12, % % 17,258 R % 5, % 7, % % 14,144 R62 1, % 23, % 23, % 5, % 53,762 R % 4, % 9, % % 14,891 R % 2, % % % 3,346 R % 7, % 5, % 1, % 15,078 R % 2, % 10, % 4, % 17,781 R % % % 0 0.0% 1,296 R % 1, % % % 2,521 R % % 2, % 1, % 4,027 R % % 10, % 1, % 14,102 R % 1, % 11, % 2, % 15,081 R % % 3, % % 4,110 R73 1, % 3, % 21, % 27, % 54,373 R % 2, % 2, % % 6,428 R75 1, % 11, % 12, % 43, % 68,880 R % 1, % 10, % 22, % 34,974 Nacimiento % 9, % 55, % 41, % 107,240 R78 1, % 8, % 13, % 2, % 26,059 R79 1, % 4, % 15, % % 20,798 R80 6, % 35, % 41, % 67, % 150,326 SanAntonio % 6, % 22, % 27, % 56,453 R % % 2, % 2, % 5,595 Table 15 4-Apr-13 Page 3 of 4 Todd Engineers

113 Paso Robles Groundwater Basin Model Update Sub-Watershed Soil Summary Sub- Watershed Group A Soils Group B Soils Group C Soils Group D Soils [%] [%] [%] [%] Total Area R83 1, % % 5, % % 8,122 R % % 2, % % 3,495 R % 8, % 5, % 14, % 28,541 R % 1, % 9, % 1, % 13,205 R % % % % 1,053 R % % 10, % 3, % 14,717 R % 1, % 10, % 3, % 16,373 R % % 2, % % 3,062 R % % % 1, % 3,619 Table 15 4-Apr-13 Page 4 of 4 Todd Engineers

114 Paso Robles Groundwter Basin Model Update Table 16 Sub-Watershed Designated Precipitation Stations and Precipitation Adjustment Factors Sub-Watershed PRISM Designated Station PRISM Adjustment Factor Isohyetal Designated Station R R R R R R R R R R R R R R R R R R R R R R Isohyetal Adjustment Factor R R R R R R R R R R R R R Apr-13 Page 1 of 3 Todd Engineers

115 Paso Robles Groundwter Basin Model Update Table 16 Sub-Watershed Designated Precipitation Stations and Precipitation Adjustment Factors Sub-Watershed PRISM Designated Station PRISM Adjustment Factor Isohyetal Designated Station Isohyetal Adjustment Factor R R R R R R R R R R R R SalinasRes R R R R R R R R R R R R R R R R R R R R R R Apr-13 Page 2 of 3 Todd Engineers

116 Paso Robles Groundwter Basin Model Update Table 16 Sub-Watershed Designated Precipitation Stations and Precipitation Adjustment Factors Sub-Watershed PRISM Designated Station PRISM Adjustment Factor Isohyetal Designated Station Isohyetal Adjustment Factor R R R R R R Nacimiento R R R SanAntonio R R R R R R R R R R Apr-13 Page 3 of 3 Todd Engineers

117 Paso Robles Groundwater Basin Model Update Regression Analysis of Evapotranspiration Data Sets Creston Days per month Month Creston in/mo) CIMIS Eto Zone 16 in/mo) RSQ r Paso Robles Days per month Month Paso Robles in/mo) CIMIS Eto Zone 16 in/mo) RSQ r Shandon Days per month Month Shandon in/mo) CIMIS Eto Zone 10 in/mo) RSQ r Tablas Creek Days per month Month Tablas Creek in/mo) CIMIS Eto Zone 6 in/mo) RSQ r Templeton Gap Days per month Month Templeton Gap in/mo) CIMIS Eto Zone 16 in/mo) RSQ r Table 18 4-Apr-13 Page 1 of 1 GEOSCIENCE Supprot Services, Inc. Todd Engineers

118