TIN/TDS Study - Phase 2A

of the

Santa Ana Watershed

Development of Groundwater Management Zones

Estimation of Historical and Current TDS and Nitrogen Concentrations in Groundwater

Final Technical Memorandum

Prepared for the TIN/TDS Task Force

July 2000

Wildermuth WE Environmental, Inc. TABLE OF CONTENTS

1. INTRODUCTION...... 1-1

2. DATA SOURCES ...... 2-1 2.1 Data Request...... 2-1 2.2 Other Data Sources...... 2-1

3. UPDATED BOUNDARY MAPS FOR MANAGEMENT ZONES ...... 3-1 3.1 Objective...... 3-1 3.2 Procedure...... 3-1 3.3 Development of Management Zone Boundaries ...... 3-3 3.3.1. and Yucaipa/Beaumont Plains...... 3-3 3.3.2. San Jacinto Basins ...... 3-10 3.3.3. Chino – Rialto/Colton – Riverside Basins...... 3-23 3.3.4. Elsinore – Temescal Valleys...... 3-41 3.3.5. Orange County Basins ...... 3-49 4. REGIONAL TDS AND NITROGEN IN GROUNDWATER ...... 4-1 4.1 Objective...... 4-1 4.2 Procedure for Estimating Regional Water Quality...... 4-1 4.2.1. Principal Changes to Original Procedure ...... 4-1 4.2.2. Procedure for Computing Regional Water Quality Used in this Study...... 4-2 4.3 Summary of Ambient Water Quality Statistics ...... 4-5 4.4 Estimation of Regional TDS and Nitrate Concentrations...... 4-6

5. COMPUTE TDS AND NITROGEN CONCENTRATIONS FOR MANAGEMENT ZONES (1973 AND 1997)...... 5-1 5.1 Objective...... 5-1 5.2 Procedure to Compute Ambient Concentrations (TDS and Nitrate) for Management Zones ...... 5-1 5.3 Details Related to Computation of Ambient Concentrations ...... 5-4

6. COMPLIANCE METRIC FOR THE AT PRADO DAM ...... 6-1 6.1 Objective...... 6-1 6.2 Existing August-Only Metric ...... 6-1 6.3 Water Quality and Quantity at and Below Prado ...... 6-2 6.3.1. Surface Water at Below Prado...... 6-2 6.3.2. Groundwater Recharge...... 6-4 6.3.3. Fate of Recharge Water ...... 6-5 6.3.4. TDS and TIN in Groundwater...... 6-6 6.3.4.1 TDS at Wells...... 6-9 6.3.4.2 TIN at Wells...... 6-11 6.4 Conclusions ...... 6-12

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7. NITROGEN LOSS COEFFICIENT ...... 7-1 7.1 Objective...... 7-1 7.2 Definitions ...... 7-1 7.3 Procedure...... 7-1 7.4 Nitrogen Losses in the Santa Ana River...... 7-2 7.4.1. Losing Reaches and Orange County Forebay...... 7-2 7.4.2. Nitrogen in the Santa Ana River and in Wells Under the Influence of the Santa Ana River ...... 7-2 7.5 Updated Data for RIX ...... 7-4 7.6 Nitrogen Loss Coefficients...... 7-4

8. REFERENCES ...... 8-1

APPENDIX A. COMPACT DISK (SEE NEXT PAGE FOR CONTENTS)

APPENDIX B. COMMENTS AND RESPONSES

APPENDIX C. DATA REQUEST LETTER AND ATTACHMENTS

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APPENDIX A. COMPACT DISK

Folder Folder Contents File/Folder Name(s) File Type Adobe Acrobat Installation files for Adobe Acrobat Reader. AdobeWin3_1.exe for MS AdobeWin3_1.exe Program Windows 3.1 and AdobeWin95_98_NT.exe for MS Windows 95, MS AdobeWin95_98_NT.exe Program Windows 98, MS Windows NT. For other operating systems, download Adobe Acrobat Reader at: http://www.adobe.com/products/acrobat/readermain.html Aquifer Layers Layer geometry data for groundwater basins where multiple aquifers were BunkerHillPressure_Layer.exe ArcView Shapefiles (zipped) delineated; data used for volumetric analysis to determine ambient water Chino_Layer.exe Surfer Grid Files (zipped) quality within management zones. OrangeCounty_Layer.exe ArcInfo Export Files (zipped) Bottom of Bottom of the freshwater aquifer geometry data for groundwater basins BunkerHill_BoA.exe ArcView Shapefiles (zipped) Aquifer where a single aquifer was delineated; data used for volumetric analysis to ChinoRiverside_BoA.exe ArcView Shapefiles (zipped) determine ambient water quality within management zones. ElsinoreTemescal_BoA.exe ArcView Shapefiles (zipped) SanJacinto_BoA.exe Surfer Grid File (zipped) Boundaries Management zone and Basin Plan subbasin boundaries for the entire Mz_boundaries.exe ArcInfo Export File (zipped) watershed. BasinPlan_boundaries.exe ArcInfo Export File (zipped) Database Microsoft Access 2000 database containing water quality, water level, well tintds_db.exe MS Access database (zipped) information, and well construction data used in the delineation of management zone boundaries and the development of ambient water quality estimates. Fonts Fonts to load for map symbology. addfonts.exe True Type Fonts (zipped) GIS Coordinate File containing description of coordinate system parameters for all GIS Coord_sys_parameters.txt Text file System coverages included on the CD. Parameters Grid 400 m x 400 m grid used in ambient water quality computations. Grid.shp ArcInfo Export File (zipped) Land Use GIS land use coverages of Orange County for 1957 and of Chino Basin for Chino_Landuse.exe ArcView Shapefiles (zipped) 1949, 1957, 1963, 1975, 1984, and 1993. OCWD_Landuse.exe JPEG image (zipped) Other Map GIS coverages of other features shown on maps in this report (includes Geology.exe ArcView Shapefiles (zipped) Features surface geology, faults, groundwater divides, rivers, lakes, roads, recharge GW_divides.exe ArcView Shapefiles (zipped) facilities, wastewater ponds, and well coverages). Lakes.exe ArcView Shapefiles (zipped) Ocwd_forebay-pressure.exe ArcView Shapefiles (zipped) Ocwd_recharge.exe ArcView Shapefiles (zipped) Rivers.exe ArcView Shapefiles (zipped) Roads.exe ArcView Shapefiles (zipped) Sanjacinto_ww_ponds.exe ArcView Shapefiles (zipped) Wells_LosingReach.exe ArcView Shapefiles (zipped) Specific Yield Specific yield data for freshwater aquifers; data used for volumetric BunkerHill_Riverside_SY.exe ArcInfo Export File (zipped) analysis to determine ambient water quality within management zones. Chino_SY.exe Text File (zipped) Elsinore_SY.exe ArcView Shapefile (zipped) OC_SY.exe ArcInfo Export Files (zipped) SanJacinto_SY.exe ArcInfo Export File (zipped)

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Folder Folder Contents File/Folder Name(s) File Type Technical Entire contents of technical memorandum Appendices (Folder) Adobe Acrobat Files Memorandum Tables_Figures (Folder) Adobe Acrobat Files Text (Folder) Adobe Acrobat Files WL Maps GIS coverages of groundwater elevation contours for Fall 1973 and Fall WL_contours (Folder) ArcView Shapefiles (zipped) 1997.

GIS coverages of wells with groundwater elevation measurements for Fall WL_wells (Folder) ArcView Shapefiles (zipped) 1973 and Fall 1997. WL Time Time histories of water levels for all wells where data were available. Lower Basin (Folder containing 811 Adobe Acrobat Files Histories files) Upper Basin (Folder containing Adobe Acrobat Files 2,326 files) WQ Maps Camera-ready originals of water quality maps for historic (1954-1973) and pdf (Folder) Adobe Acrobat Files current (1978-1997) time periods.

GIS coverages of water quality contours for historic (1954-1973) and WQ_Contours (Folder) ArcView Shapefiles (zipped) current (1978-1997) time periods.

GIS coverages of wells with water quality point statistics for historic WQ_Wells (Folder) ArcView Shapefiles (zipped) (1954-1973) and current (1978-1997) time periods.

WQ Statistics Summary of computed statistics for ambient water quality – Upper Basin Ambient_WQ_UB.exe MS Excel (zipped) (UB) and Lower Basin (LB) Ambient_WQ_LB.exe MS Excel (zipped) WQ Time Time histories of nitrate and TDS for all wells where data were available. Lower Basin (Folder containing Adobe Acrobat Files Histories 1,284 files) Upper Basin (Folder containing Adobe Acrobat Files 1,736 files) Time histories of nitrate and TDS for wells and surface water used in the analysis of nitrogen loss coefficients (Task 1) and compliance metrics for Task1&Task2 (Folder containing Adobe Acrobat Files the Santa Ana River (Task 2). 867 files)

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM

LIST OF TABLES

2-1 List of Agencies Queried for Data 2-2 Data Sources 3-1 References Cited by Groundwater Basins and Management Zones 5-1 Historical and Current Ambient Water Quality by Management Zones 6-1 TDS and Recharge at OCWD-SAR Recharge Facilities 6-2 Water Character Index for Source Waters and Groundwater 7-1 Literature Values of Nitrogen Loss Coefficients 7-2 Nitrogen Loss Coefficients and TIN Limitations for Santa Ana Watershed

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LIST OF FIGURES

3-1 Elevation Contours of the Effective Base of Freshwater Aquifers – San Bernardino Valley & Yucaipa/Beaumont Plains 3-2 Fall 1973 Groundwater Elevation Contours & Management Zone Boundaries – San Bernardino Valley & Yucaipa/Beaumont Plains 3-3 Fall 1997 Groundwater Elevation Contours & Management Zone Boundaries – San Bernardino Valley & Yucaipa/Beaumont Plains 3-4 Preliminary Management Zone Boundaries – San Bernardino Valley & Yucaipa/Beaumont Plains 3-5 Elevation Contours of the Effective Base of Freshwater Aquifers – San Jacinto Basins 3-6 Fall 1973 Groundwater Elevation Contours & Management Zone Boundaries – San Jacinto Basins 3-7 Fall 1997 Groundwater Elevation Contours & Management Zone Boundaries – San Jacinto Basins 3-8 Preliminary Management Zone Boundaries – San Jacinto Basins 3-9 Elevation Contours of the Effective Base of Freshwater Aquifers – Chino, Rialto-Colton, & Riverside Basins 3-10 Fall 1973 Groundwater Elevation Contours & Management Zone Boundaries – Chino, Rialto- Colton, & Riverside Basins 3-11 Fall 1997 Groundwater Elevation Contours & Management Zone Boundaries – Chino, Rialto- Colton, & Riverside Basins 3-12 Preliminary Management Zone Boundaries – Chino, Rialto-Colton, & Riverside Basins 3-13 Elevation Contours of the Effective Base of Freshwater Aquifers – Elsinore/Temescal Valleys 3-14 Fall 1973 Groundwater Elevation Contours & Management Zone Boundaries – Elsinore/Temescal Valleys 3-15 Fall 1997 Groundwater Elevation Contours & Management Zone Boundaries – Elsinore/Temescal Valleys 3-16 Preliminary Management Zone Boundaries – Elsinore/Temescal Valleys 3-17 Elevation Contours of the Effective Base of Freshwater Aquifers – Orange County Basins 3-18 Fall 1973 Groundwater Elevation Contours & Management Zone Boundaries – Orange County Basins 3-19 Fall 1997 Groundwater Elevation Contours & Management Zone Boundaries – Orange County Basins 3-20 Preliminary Management Zone Boundaries – Orange County Basins 5-1a Historical Ambient Water Quality – Total Dissolved Solids, 1954-1973 5-1b Current Ambient Water Quality – Total Dissolved Solids, 1978-1997 5-2a Historical Ambient Water Quality – Nitrate-N, 1954-1973

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5-2b Current Ambient Water Quality – Nitrate-N, 1978-1997 5-3 Difference in Ambient Water Quality (Historical minus Current) – Total Dissolved Solids 5-4 Difference in Ambient Water Quality (Historical minus Current) – Nitrate-N 6-1 Reference Map 6-2a TDS and Daily Flow at Below Prado 6-2b TDS and Components of Flow at Below Prado 6-3a TIN and Daily Flow at Below Prado 6-3b TIN and Components of Flow at Below Prado 6-4 Components of Recharge at OCWD-SAR Recharge Facilities 6-5 Water Character Index as a Function of Time for Orange County MZ Groundwater and Various Source Waters 6-6 Water Character Index in the Orange County Basin 6-7a Average TDS in Groundwater 1964 – 1966 (End of Dry Period) 6-7b Average TDS in Groundwater 1969 – 1971 (End of Wet Period) 6-7c Average TDS in Groundwater 1975 – 1977 (End of Dry Period) 6-7d Average TDS in Groundwater 1985 – 1987 (End of Wet Period) 6-7e Average TDS in Groundwater 1990 – 1992 (End of Dry Period) 6-8a Average Nitrate-N in Groundwater 1964 – 1966 (End of Dry Period) 6-8b Average Nitrate-N in Groundwater 1969 – 1971 (End of Wet Period) 6-8c Average Nitrate-N in Groundwater 1975 – 1977 (End of Dry Period) 6-8d Average Nitrate-N in Groundwater 1985 – 1987 (End of Wet Period) 6-8e Average Nitrate-N in Groundwater 1990 – 1992 (End of Dry Period) 6-9 TDS Interval Contour Map

6-10 NO3-N Interval Contour Map 6-11 TDS of Water Recharged at OCWD-SAR Recharge Facilities 6-12 Wells Receiving Groundwater within 25 Years at OCWD-SAR Recharge Facilities 6-13a Comparison of TDS in Groundwater Downgradient of OCWD-SAR Recharge Facilities and TDS of SAR at Below Prado 6-13b Comparison of TDS in Groundwater Near OCWD-SAR Recharge Facilities and TDS of SAR at Below Prado 6-14a Comparison of Nitrate-N in Groundwater Downgradient of OCWD-SAR Recharge Facilities and TIN of SAR at Below Prado 6-14b Comparison of Nitrate-N in Groundwater Near OCWD-SAR Recharge Facilities and TIN of SAR at Below Prado 6-15 Comparison of Current Reach 2 and Reach 3 TDS Metrics of the Santa Ana River

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7-1 Wells Potentially Under the Influence of the Santa Ana River with Fall 1997 Groundwater Elevation Contours – Upper Santa Ana Basin 7-2 Wells Potentially Under the Influence of the Santa Ana River with Groundwater Flow Vectors – Upper Santa Ana Basin 7-3 Wells Potentially Under the Influence of the Santa Ana River with Fall 1997 Groundwater Elevation Contours – Lower Santa Ana Basin 7-4 Average Nitrate in Groundwater (1954 to 1973) in the Losing Reach of the Santa Ana River – Upper Santa Ana Basin 7-5 Average Nitrate in Groundwater (1954 to 1973) in the Losing Reach of the Santa Ana River with 1949 Land Use – Upper Santa Ana Basin 7-6 Average Nitrate in Groundwater (1954 to 1973) in the Losing Reach of the Santa Ana River with 1957 Land Use – Upper Santa Ana Basin 7-7 Average Nitrate in Groundwater (1954 to 1973) in the Losing Reach of the Santa Ana River with 1963 Land Use – Upper Santa Ana Basin 7-8 Average Nitrate in Groundwater (1978 to 1997) in the Losing Reach of the Santa Ana River – Upper Santa Ana Basin 7-9 Average Nitrate in Groundwater (1978 to 1997) in the Losing Reach of the Santa Ana River with 1975 Land Use – Upper Santa Ana Basin 7-10 Average Nitrate in Groundwater (1978 to 1997) in the Losing Reach of the Santa Ana River with 1984 Land Use – Upper Santa Ana Basin 7-11 Average Nitrate in Groundwater (1978 to 1997) in the Losing Reach of the Santa Ana River with 1993 Land Use – Upper Santa Ana Basin 7-12 Average Nitrate in Groundwater (1954 to 1973) in the Orange County Forebay – Lower Santa Ana Basin 7-13 Average Nitrate in Groundwater (1978 to 1997) in the Orange County Forebay – Lower Santa Ana Basin 7-14 Average Nitrate in Groundwater (1954 to 1973) in the Orange County Forebay with 1957 Land Use – Lower Santa Ana Basin 7-15 TIN Concentrations at RIX (monthly averages) 7-16 TIN Concentrations at RIX (annual moving averages)

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ACRONYM AND ABBREVIATIONS LIST

mg/L micrograms per liter mmhos/cm micromhos per centimeter ADFM accumulated departure from the mean bgs below ground surface Ca calcium CBWCD Chino Basin Water Conservation District CD compact disk CD-ROM compact disk-read only memory Cl chloride CU color units DHS Department of Health Services DWR California Department of Water Resources EC electrolytic conductivity EMWD Eastern Municipal Water District EVMWD Municipal Water District F fluoride GIS geographic information system HAA haloacetic acid IEUA Utilities Agency K potassium LB Lower (Santa Ana) Basin LLNL Lawrence Livermore National Laboratories MCL maximum contaminant level meq/L milliequivalents per liter MFL Million Fibers per Liter Mg magnesium mg/L milligrams per liter MPN most probable number MS Microsoft MWD Metropolitan Water District of MWDSC Metropolitan Water District of Southern California

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Na sodium ND not detected

NO3 nitrate

NO3-N nitrate as nitrogen NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Unit OCSD Orange County Sanitation District OCWD Orange County Water District OCWD Orange County Water District pdf portable document format RWQCB State of California Regional Water Quality Control Board SAR Santa Ana River SEM standard error of the mean

SiO3 silica

SO4 sulfate SWP State Water Project T temperature TDS total dissolved solids THM trihalomethane TIN total inorganic nitrogen RWQCB Regional Water Quality Control Board, Santa Ana Region SBVMWD San Bernardino Valley Municipal Water District SBVWCD San Bernardino Valley Water Conservation District SAWPA Santa Ana Watershed Project Authority USGS US Geological Survey JCSD Jurupa Community Services District YVWD Yucaipa Valley Water District TOC total organic carbon TTHM total trihalomethane UB Upper (Santa Ana) Basin WE, Inc. Wildermuth Environmental, Inc. WWTP wastewater treatment plant

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM

Acknowledgments WE Inc. gratefully acknowledges the assistance of the Task Force Members and the following individuals and organizations for their review and comments on interim work products:

Doug Drury Inland Empire Utilities Agency Bernard Kersey City of San Bernardino Water Department Behrooz Mortazavi Eastern Municipal Water District Robert Nicklen Regional Water Quality Control Board Mark Norton Santa Ana Watershed Project Authority P. Ravishanker Eastern Municipal Water District Joanne Schneider Regional Water Quality Control Board Hope Smythe Regional Water Quality Control Board Gerald Thibeault Regional Water Quality Control Board Don Williams City of Corona Greg Woodside Orange County Water District

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM

Disclaimer The authorized use of these data is limited to basin planning purposes only, and not for design. No warranty expressed or implied is made regarding the accuracy or utility of these data for any other purpose other than that stated in the introduction of this report, nor shall the act of distribution of these data constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. WE, Inc. and the TIN/TDS Task Force shall not be held liable for improper or incorrect use of the data described and/or contained herein. WE, Inc. and the TIN/TDS Task Force assume no legal responsibility for the user’s reliance, use, or interpretation of the data provided herein. WE, Inc. and the TIN/TDS Task Force shall not be liable for any loss or injury resulting from reliance upon the information shown.

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1. INTRODUCTION

A Task Force was formed to provide oversight, supervision, and approval of a study to evaluate the impact of Total Inorganic Nitrogen (TIN) and Total Dissolved Solids (TDS) on water resources in the Santa Ana Watershed. Members of the TIN/TDS Task Force include:

· Chino Basin Water Conservation District (CBWCD)

· Chino Basin Watermaster

· City of Colton

· City of Corona

· City of Redlands

· City of Rialto

· City of Riverside

· City of San Bernardino

· Eastern Municipal Water District (EMWD)

· Elsinore Valley Municipal Water District (EVMWD)

· Inland Empire Utilities Agency (IEUA)

· Jurupa Community Services District (JCSD)

· Metropolitan Water District of Southern California (MWDSC)

· Orange County Sanitation District (OCSD)

· Orange County Water District (OCWD)

· Regional Water Quality Control Board, Santa Ana Region (RWQCB) – Advisory Member

· Riverside-Highland Water Company

· San Bernardino Valley Municipal Water District (SBVMWD)

· San Bernardino Valley Water Conservation District (SBVWCD)

· Santa Ana Watershed Project Authority (SAWPA) – Advisory Member

· US Geological Survey (USGS) – Advisory Member

· West San Bernardino County Water District

· Yucaipa Valley Water District (YVWD) Wildermuth Environmental, Inc. (WE, Inc.) was retained by the TIN/TDS Task Force, through a contract administered by SAWPA, to conduct Phase 2A of the Total Inorganic Nitrogen/Total Dissolved Solids Study (Task Order 1998-W020-1616-03). The Task Force approved a scope of work prepared by Mark J. Wildermuth, Water Resources Engineer (dba WE, Inc.) and Risk Sciences, entitled, “Conceptual Study Design to Review Existing Water Quality Objectives, Wasteload Allocations & Monitoring Programs for Inorganic Nitrogen (TIN) & Dissolved Solids in the Santa Ana River Watershed and to Develop Appropriate Alternatives Where Necessary” dated March 24, 1995. Phase 2A is comprised of the following tasks:

· Task 1: Develop Surface Water Translator for Meeting Groundwater Objectives that Accounts for Nitrogen Losses During Percolation

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· Task 2: Develop New Compliance Metric and Monitoring Plan to Replace Current August- Only Below Prado Metric

· Task 3: Develop Updated Boundary Maps for Groundwater Subbasins and New Management Zones

· Task 4: Estimate Regional TDS and Nitrogen Concentrations in Groundwater

· Task 5: Compute TDS and Nitrogen Objectives for New Groundwater Basins and Management Areas Technical memoranda for Tasks 1, 2, and 5 were defined in the original scope of work. A technical memorandum describing the results of Task 3 was included in Change Order 1 to the contract. This document combines the technical memoranda for Tasks 2, 3, and 5.

The technical memorandum for Task 1 was submitted as a draft in October 1998 and as a draft final in November 1998. Change Order 3 to the contract is an additional scope item in Task 2 to assess historical nitrogen losses from losing reaches of the Santa Ana River. The results of this change order, including updated conclusions and recommendations, are included in this document as well. Additional data reviewed as part of this change order, including data from RIX between March 1998 and September 1999, are included in this document. The Task 1 Technical Memorandum is considered a final document, given approval of the additional analyses and conclusions presented herein. An insert for inclusion with the Task 1 Technical Memorandum will be developed and submitted with this final document. This insert will summarize the final conclusion reached by the Task Force.

All tabular data (water quality, water level, well information, et cetera) have been compiled into a Microsoft (MS) Access database. This database on the CD-ROM (Appendix A).

Therefore, all documentation for Phase 2A is contained in the following three documents/deliverables:

· Wildermuth Environmental, Inc. 1998b. TIN/TDS Phase 2A: Task 1-4. Nitrogen Losses from Recycled Water Systems. Draft Final Technical Memorandum. November 1998. [now final]

· Wildermuth Environmental, Inc. 2000. TIN/TDS Phase 2A: Tasks 1 through 5. TIN/TDS Study of the Santa Ana Watershed. Technical Memorandum. July 2000. [this document]

· Wildermuth Environmental, Inc. 2000. TIN/TDS Phase 2A: MS Access Database for TIN/TDS Study of the Santa Ana Watershed. Technical Memorandum. July 2000. [Appendix A] This technical memorandum contains the following sections:

Section Task Contents 1 All Introduction

2 4 Section 2 is a summary of all the sources of data that were compiled and used in the Phase 2A study.

3 3 Section 3 is the technical memorandum specified in Change Order 1 for Task 3. This section provides documentation for the scientific and engineering decisions made in developing management zones. The documentation is of sufficient detail and clarity such that non-Task

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 1 - INTRODUCTION

Section Task Contents Force entities will be able to reconstruct the proposed management zones by applying the logic and decisions outlined in this section.

4 4 Section 4 describes the development of point statistics at wells that would represent ambient conditions for nitrate and TDS in groundwater for an historical period and for the current period. The point statistics were then used to develop regional estimates of nitrate and TDS in groundwater.

5 5 Section 5 describes the derivation of historical and current ambient conditions for each management zone from regional estimates developed in Task 4.

6 2 Section 6 describes the existing compliance metric for the Santa Ana River at Prado Dam, and reviews existing data to determine if new metrics can be developed that are equally protective of the Orange County groundwater basin and allow more upstream reclamation.

7 1 Section 7 summarizes the analyses for the nitrogen loss coefficient. The section summarizes the data reviewed for the losing reaches of the Santa Ana River and recent data from RIX that were not available when the Task 1 Draft Final Technical Memorandum was published.

8 All References

Appendix 3 - 5 Appendix A is a CD that contains data used in developing ambient water A quality estimates for management zones. The table of contents provides a detailed list of files on the CD.

Appendix 4 Appendix B is a compilation of responses to comments received from B the Task Force on the Phase 2A Draft Final Technical Memorandum.

Appendix 4 Appendix C is the letters and attachments sent to state and local agencies C requesting the data that was compiled and used in this study.

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2. DATA SOURCES

The following section describes the data collection process and summarizes the sources of data that were compiled and used in the Phase 2A study.

2.1 Data Request

During Phase 1A of the current TIN/TDS Study various groundwater, surface water, wastewater, and climatic data were collected, compiled, and reviewed from federal, state, and local agencies (Mark J. Wildermuth, 1997a). At the onset of Phase 2A, agencies that submitted data during Phase 1A were sent a data request letter asking for updated information. Agencies that did not submit data during Phase 1A were sent a data request letter for all relevant information. These data request letters and attachments are included in Appendix C.

The general types of data requested included well construction, well location, groundwater quality, and groundwater level data. A detailed description of data requested is included as an attachment to the data request letter in Appendix C. In addition, reports and publications that describe the hydrogeologic nature of the groundwater reservoirs in the area were requested from all agencies. The agencies that were sent data request letters as part of Phase 2A are listed in Table 2-1.

2.2 Other Data Sources

Other data were also necessary for volume-weighted calculations of ambient water quality, which included specific yield coverages, base of the freshwater geometry, and aquifer geometry (where multiple layered aquifers exist). These data were primarily collected from previous investigations, which are listed in Table 2-2, referenced in Section 8, and included as geographic coverages on the CD that accompanies this report (Appendix A).

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3. UPDATED BOUNDARY MAPS FOR MANAGEMENT ZONES

3.1 Objective

The objective of Task 3 is to develop spatial boundaries for groundwater management zones – formerly called subbasins in previous Basin Plans – in the Santa Ana River and San Jacinto River watersheds (hereafter collectively referred to as “the watershed”). Management zones were developed to be consistent with the groundwater flow regime in the basin and to include well-defined areas of recharge and discharge. Using these criteria to develop management zones, the associated water quality of the recharge and discharge terms can be estimated and managed effectively (Mark J. Wildermuth, 1998).

Management zones are defined herein as hydrologically-distinct groundwater units from a groundwater flow and water quality perspective. Groundwater flow was the principal phenomena studied and utilized to construct management zones; water quality data were used to augment our understanding of the flow regime.

3.2 Procedure

As mentioned above, management zones are defined as hydrologically-distinct groundwater units from a groundwater flow and water quality perspective. As such, lines delineating management zones were placed along impermeable barriers to groundwater flow, at bedrock constrictions, and between distinct flow systems. Groundwater flow between management zones is generally restricted. Exceptions were encountered in certain areas and are discussed in Section 3.3.

In order to develop “flow-based” management zones, a thorough understanding of (1) the impermeable boundaries that delineate the major groundwater basins and (2) the groundwater flow systems within the major groundwater basins is necessary. The procedure to develop management zones included:

1. Review of literature. The groundwater resources within the watershed have been studied and documented by various entities dating to the early 1900s. This literature was collected and reviewed, with special attention to the physical features that bound the major groundwater basins (e.g., bedrock, faults), groundwater flow systems, water quality studies that indicate groundwater flow directions, and maps that depict all of the above features. The publications utilized for this task are referenced in Section 8 and listed in Table 3-1.

2. Digitization of established geologic/fault maps. Some of the geologic maps collected through the literature review were digitized and brought into a geographic information system (GIS) as ArcInfo coverages. The main features digitized from these maps were (1) the geologic contacts between the consolidated bedrock (non-water bearing), semiconsolidated sediments (possibly water bearing), and unconsolidated sediments (water bearing), and (2) the surface traces of faults and groundwater barriers. Typically, these features bound the major groundwater basins within the watershed and are displayed as the background coverages on nearly all maps included in this memorandum. If warranted, they were used to delineate management zone boundaries.

It should be noted that the terms used throughout this report to describe bedrock, such as “consolidated,” “non-water bearing,” and “impermeable,” are used in a relative sense. The water content and permeability of these bedrock formations, in fact, is not zero. However, the primary point is that the permeability of the geologic formations in the areas flanking the basin is much less than the aquifers in the groundwater basins.

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3. Determination of bedrock elevation and hydrostratigraphy. The subsurface contact between non-water-bearing bedrock and the water-bearing alluvial sediments is herein referred to as the “bedrock elevation.” Typically, this contact is represented by a bedrock elevation contour map generated from driller’s logs of wells that penetrated bedrock and/or geophysical studies. Bedrock elevation data were collected from various sources (see Table 3-1 and Section 8), but also included some original work performed for this study. The data were used to develop a three- dimensional representation of the major groundwater basins. In some areas, bedrock elevation maps provided insight to groundwater flow directions, revealed subsurface bedrock constrictions, and aided in the proper placement of management zone boundaries.

In major portions of the Bunker Hill, Chino, and Orange County groundwater basins, the geologic stratification is such that major aquifers exist as vertically-separated, distinct hydrologic zones. Groundwater often exists under confined or pressurized conditions within the deeper aquifers in these areas. These stratified aquifers were delineated within the groundwater basins for work performed in Task 4, but were not defined as unique management zones since hydraulic continuity exists between forebay areas and the stratified aquifers.

4. Construction of groundwater elevation contour maps. At least two groundwater elevation contour maps were generated to determine the nature and consistency of groundwater flow systems (i.e., flow directions and/or saddle surfaces) within all the major groundwater basins in the watershed. Groundwater elevation contour maps for Fall 1973 and Fall 1997 were constructed for each major groundwater basin. These maps are displayed in Section 3.3. In many cases, additional groundwater elevation contour maps were constructed to add robustness to the flow system analysis. The procedure for constructing groundwater elevation contour maps follows:

· Collect historical groundwater elevation data for wells within the watershed. Main data sources included files from the California Department of Water Resources (DWR), Western Municipal Water District, Chino Basin Watermaster, Eastern Municipal Water District, and Orange County Water District. Other sources included the various water agencies and entities that own wells within the watershed and collect groundwater elevation data on a periodic basis.

· Plot groundwater elevation time histories for all wells versus an accumulative departure from the mean (ADFM) curve. The ADFM curve is a representation of climate/precipitation over time and, when plotted with a groundwater elevation time history, aids in understanding groundwater elevation fluctuations. As a whole, the time history plots can be used to distinguish between static and pumped groundwater levels. Groundwater elevation data that were collected while the well was under the influence of pumping was discarded for the construction of groundwater elevation contour maps.

· Extract groundwater elevation data for a certain time period. For example, for the Fall 1973 groundwater elevation contour maps, we extracted groundwater elevation data for wells with data between September 1 and December 31, 1973. After “pumping” data was discarded, we chose one groundwater elevation data point for each well in the following order of priority: November, October, December, September. If two or more data points existed for a given month, we chose the shallowest data point with the assumption that the shallowest data point represented the “most static” water level reading for that month.

· Plot groundwater elevation data on maps with background geologic/fault coverages. Well location information (including GPS locations, well location maps, and driller’s log location descriptions) was collected from various data sources. Well locations then had to be matched to the groundwater elevation data in order to plot the groundwater elevation data. If well location information was unavailable, then an estimated location was assigned to the data based on the state well numbering system.

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· Contour and digitize groundwater elevation data. Groundwater elevation contours were hand drawn based on the plotted groundwater elevation point (well) data. In addition to the geologic/fault coverages, surface hydrology was also included as background coverages on the contour maps. Knowledge of the basin’s geometry and hydrology – which included geology, surface water drainage patterns, locations of areas of artificial and natural recharge and discharge, and orientation of known groundwater contamination plumes – helped in the construction of groundwater elevation contours on all maps. The groundwater elevation contours were digitized and projected into the project GIS. The groundwater elevation contour maps were used to analyze and interpret groundwater flow directions (perpendicular to the groundwater elevation contours) within the major groundwater basins. Our maps and interpretations were always compared to maps and interpretations found in the literature review. When two or more consistent flow systems within a larger groundwater basin were documented to exist over time (through variations in climate and/or pumping), the groundwater elevation contours maps were then used to draw management zone boundaries between the flow systems.

Management zone boundaries based on groundwater flow systems are not as stationary or reliable as impermeable bedrock boundaries or fault boundaries. While a boundary between flow systems is drawn as a line, in reality, it may exist more as a narrow zone – the actual boundary oscillating within this zone over time in response to changes in climate and/or pumping. With a few exceptions, our analysis of flow systems throughout the watershed revealed consistency of flow systems over time. The consistency of flow systems and its implications for management zone boundaries is discussed in Section 3.3.

5. Discussions with experts. Commonly, we would seek the opinions of groundwater hydrologists and/or geologists that have performed work within certain areas of the watershed. Their opinions were used to confirm our conclusions and/or to resolve uncertainties regarding groundwater flow systems and management zone boundaries. The significant discussions are referenced in Section 9.

3.3 Development of Management Zone Boundaries

As described above, the groundwater flow systems within the watershed were delineated and used to construct management zone boundaries. This section describes the groundwater flow systems by major groundwater basin and by individual management zone. Detailed descriptions of surface and groundwater hydrology within the watershed, including descriptions of climate, geology, structure, groundwater movement and hydrologic budget, can be found in the Phase 1A Task 2.2 and 2.3 Final Report (Mark J. Wildermuth, 1997b).

3.3.1 San Bernardino Valley and Yucaipa/Beaumont Plains

The San Bernardino Valley and Yucaipa/Beaumont Plains overlie part of a larger, broad, alluvial-filled basin located between the San Gabriel/ to the north and the elevated / to the south. The Santa Ana River is the main tributary draining this large basin. Sediments eroded from igneous and metamorphic rocks within the surrounding mountains have filled this basin to provide reservoirs for groundwater. The San Jacinto Fault cuts through this alluvial- filled basin from northwest to southeast to form a major barrier to groundwater flow and, hence, separates the groundwater basins of the San Bernardino Valley and Yucaipa/Beaumont Plains in the east from the groundwater basins of the Chino, Rialto-Colton, and Riverside areas in the west.

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The San Bernardino Valley and the Yucaipa/Beaumont Plains overlie a number of fault-separated groundwater basins located between the active San Andreas and San Jacinto Fault Zones. Figure 3-1 is an equal elevation contour map of the effective base of the freshwater aquifers in this region. Note the highly-faulted nature of the San Bernardino Valley and Yucaipa/Beaumont Plains. This region has been sub-divided into many smaller groundwater basins in past studies – especially in the Lytle Creek and Yucaipa/Beaumont areas (Burnham & Dutcher, 1960; Dutcher & Garrett, 1963; Dutcher & Fenzel, 1972).

The faults within this area vary in their effectiveness as barriers to groundwater flow – the most competent barriers often chosen as management zone boundaries, as will be discussed below. These faults, their effects on groundwater movement, and groundwater movement in general have been studied in detail by the USGS and DWR (Eckis, 1934; Gleason, 1947; Burnham & Dutcher, 1960; Dutcher & Garrett, 1963; Dutcher & Fenzel, 1972; Izbicki et al., 1998).

Predominant recharge to the groundwater reservoirs in this area is from infiltration of stream flow out of the San Gabriel and San Bernardino Mountains. In general, groundwater flow mimics surface drainage patterns: from the areas of recharge at the apexes of alluvial cones along the mountain fronts towards the area of discharge where groundwater leaks across San Jacinto Fault in the vicinity of the Santa Ana River. Figures 3-2 and 3-3 are groundwater elevation contour maps for Fall 1973 and Fall 1997 that show this general groundwater flow pattern. Note that groundwater flow paths (perpendicular to the contours) start in the various areas of recharge and converge upon the main area of natural discharge where the Santa Ana River crosses the San Jacinto Fault.

This “convergence zone” (commonly referred to as the Pressure Zone) is a historical area of flowing wells and rising water within streambeds. Dutcher & Garrett (1963) delineated the Pressure Zone as the “original limit of flowing wells.” The Pressure Zone also coincides with the deepest (see Figure 3-1) and most geologically stratified portion of the basin. Dutcher & Garrett (1963) developed a three-layer representation of the water-bearing and confining sedimentary units underlying this area, which was the model used in our calculations of ambient water quality within the Pressure Zone (described in Section 4).

We have delineated five management zones within the San Bernardino Valley and Yucaipa/Beaumont Plains based on major impermeable boundaries, groundwater/watershed divides, and internal flow systems (Figure 3-4):

· Bunker Hill-A

· Bunker Hill-B

· Lytle

· Yucaipa

· San Timoteo

Management Zone: Bunker Hill-A

Recharge

· Infiltration of flow within the channels of Cajon Creek and other streams overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

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· Artificial recharge of imported and native waters at spreading grounds below Devil Canyon and East Twin-Waterman Canyon.

· Intermittent underflow from Lytle management zone across Loma Linda Fault and/or Barrier G.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· From Cajon Pass/Cajon Creek to the southeast towards the Shandin Hills.

· North of Shandin Hills, flow is southeast and thence due south staying west of Perris and into the Pressure Zone.

· South of Shandin Hills, flow is southeast and into the Pressure Zone. Discharge

· Groundwater production.

· Underflow to Colton management zone across San Jacinto Fault near Santa Ana River.

· Intermittent underflow to Lytle management zone across Loma Linda Fault and/or Barrier G. Boundaries

· San Andreas Fault/San Bernardino Mountains to the northeast. The San Andreas is a major active fault zone and a known groundwater barrier. The southern-most lineament was chosen and mapped as the management zone boundary.

· Bedrock constriction in Cajon Canyon to the northwest. The impermeable bedrock constricts and the alluvial aquifer thins northwest of Devore in Cajon Canyon. The management zone boundary was mapped at this constriction about 0.3 miles northwest of the City of San Bernardino’s northern-most well field (Kenwood, Vincent, and Cajon Canyon wells).

· Loma Linda Fault, Barrier G, San Jacinto Fault to the southwest. These faults and barriers separate Bunker Hill-A from the Lytle, Rialto, and Colton management zones. The locations of these faults and barriers were based on the work of Dutcher & Garrett (1963), who described hydraulic discontinuity across these features through analysis of well water- level time histories.

· Flow system boundary with Bunker Hill-B to the east. Comparison of groundwater level contour maps over time demonstrates a distinction between the flow systems of Bunker Hill- A and Bunker Hill-B (Figures 3-2 and 3-3). Water recharged north of Perris Hill (e.g., within the East Twin-Waterman Spreading Grounds) commingles with groundwater flowing around the northern flank of the Shandin Hills and, thence, flows due south, west of Perris Hill, into the Pressure Zone. Water recharged northeast of Perris Hill (e.g., within Warm Creek and City Creek) flows to the southeast, east of Perris Hill, and into the Pressure Zone. The management zone boundary that separates these flow systems is approximately parallel to groundwater flow directions and runs from the San Bernardino Mountain front east of the East Twin-Waterman Spreading Grounds to Perris Hill. The boundary is less distinct south of Perris Hill in the Pressure Zone, and is probably influenced by changes in climate and local pumping patterns. However, the boundary is essentially aligned along the course of Warm Creek to the San Jacinto Fault.

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Management Zone: Bunker Hill-B

Recharge

· Infiltration within the channels and floodplains of the upper-most Santa Ana River and Mill Creek.

· Infiltration of flow within other unlined stream channels overlying the management zone (e.g. Warm, City, and Plunge Creeks).

· Artificial recharge of imported and native waters at spreading grounds along the upper-most Santa Ana River and Mill Creek.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Minor underflow from Yucaipa and San Timoteo management zones.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Recharge in and around the upper-most Santa Ana River and Mill Creek dominates the groundwater hydrology. Flow is generally from these areas due west into the Pressure Zone, with relatively minor groundwater input from areas of recharge to the north and south. Discharge

· Groundwater production.

· Underflow to Colton management zone across the San Jacinto Fault near the Santa Ana River. Boundaries

· San Andreas Fault/San Bernardino Mountains to the northeast. The San Andreas is a major active fault zone and a known groundwater barrier. The southern-most lineament was chosen and mapped as the management zone boundary.

· Crafton Hills, Banning Fault, and Redlands Fault to the southeast. The Crafton Hills are an elevated ridge of impermeable bedrock separating the Bunker Hill-B and Yucaipa management zones. North of the Crafton Hills, the management zone boundary crosses a narrow fault trough between the Oak Glen Fault and the San Andreas Fault. Limited groundwater flow from the Yucaipa management zone may cross this boundary into Bunker Hill-B. South of the Crafton Hills, the boundary follows the Redlands Fault to the Banning Fault and, thence, to the Loma Linda Fault. Here, the boundary arbitrarily crosses a low- permeable portion of the San Timoteo Badlands to the San Jacinto Fault. The Redlands and Banning faults are known barriers to groundwater flow, but groundwater leakage occurs across these faults from the Yucaipa and San Timoteo management zones into Bunker Hill-B (Burnham and Dutcher, 1960; Dutcher and Fenzel, 1972).

· San Jacinto Fault to the southwest. The San Jacinto Fault separates Bunker Hill-B from the Colton management zone. Along most of its trace, the San Jacinto Fault is a competent barrier to groundwater flow. However, the USGS has documented and estimated leakage across the San Jacinto Fault in the vicinity of its intersection with the Santa Ana River. This groundwater leakage to the Colton management zone is likely through the upper, river- channel deposits (Dutcher & Garrett, 1963; Woolfenden and Kadhim, 1997).

· Flow system boundary with Bunker Hill-A to the northwest. Comparison of groundwater level contour maps over time demonstrates a distinction between the flow systems of Bunker

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Hill-A and Bunker Hill-B (Figures 3-2 and 3-3). Water recharged north of Perris Hill (e.g., within the East Twin-Waterman Spreading Grounds) commingles with groundwater flowing around the northern flank of the Shandin Hills and, thence, flows due south, west of Perris Hill, into the Pressure Zone. Water recharged northeast of Perris Hill (e.g., within Warm Creek and City Creek) flows to the southeast, east of Perris Hill, and into the Pressure Zone. The management zone boundary that separates these flow systems is approximately parallel to groundwater flow directions and runs from the San Bernardino Mountain front east of the East Twin-Waterman Spreading Grounds to Perris Hill. The boundary is less distinct south of Perris Hill in the Pressure Zone, and is probably influenced by changes in climate and local pumping patterns. However, the boundary is essentially aligned along the coarse of Warm Creek to the San Jacinto Fault.

Management Zone: Lytle

Recharge

· Infiltration within the channels and floodplains of Lytle Creek and Cajon Creek.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock hills.

· Artificial recharge of native waters at spreading grounds along Lytle Creek.

· Intermittent underflow from Bunker Hill-A across the Loma Linda Fault and Barrier G.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Recharge in Lytle Creek north of Barrier J either leaks across Barrier J and flows southeast into the Lytle management zone proper, or is diverted by Barrier J to the west and flows toward the Rialto and Chino basins. The Lytle management zone is segmented into several “compartments” by a number of groundwater barriers (named by Dutcher and Garrett, 1963). Groundwater flow is generally to the southeast toward the southern portion of the management zone; however, leakage occurs across the groundwater barriers between compartments and neighboring management zones. Groundwater level data was not sufficient to draw groundwater elevation contours within the compartments of the Lytle management zone (Figures 3-2 and 3-3). Discharge

· Groundwater production.

· Intermittent underflow to Bunker Hill-A management zone across Loma Linda Fault and Barrier G.

· Intermittent underflow to Rialto and Chino management zones across Barrier E and its extension north of Barrier J. Boundaries

· Loma Linda Fault and Barrier G to the northeast. The Loma Linda Fault and Barrier G, as mapped and described by Dutcher and Garrett (1963), are barriers to groundwater flow. Groundwater level time histories at wells on opposite sides of these features indicate hydraulic discontinuity. In addition, some wells directly west of Barrier G were reported to be flowing wells in the early 1900s. Leakage across these features likely occurs in both directions between Lytle and Bunker Hill-A management zones depending on climate and pumping patterns (Dutcher and Garrett, 1963).

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· San Jacinto Fault and Barrier E and its extension north of Barrier J to the southwest. The San Jacinto Fault and Barrier E (and its extension north of Barrier J) separate the Lytle and Rialto management zones. South of Barrier J, the San Jacinto Fault and Barrier E are competent barriers to groundwater flow as indicated by higher groundwater elevations within the Lytle management zone (Dutcher and Garrett, 1963). North of Barrier J, there is little evidence of the extension of Barrier E to the San Gabriel Mountains. Groundwater likely flows across the extension of Barrier E north of Barrier J into the Rialto management zone. Some underflow also may occur across Barrier E south of Barrier J into the Rialto management zone (Woolfenden and Kadhim, 1997).

· San Gabriel Mountains and the mouth of Lytle Creek Canyon to the northwest. The San Gabriel Mountains are composed of impermeable bedrock. The northern-most boundary of the Lytle management zone was chosen at the bedrock constriction at the mouth of Lytle Creek Canyon.

Management Zone: Yucaipa

Recharge

· Infiltration within the channels of streams overlying the management zone (Yucaipa and Oak Glen Creeks, for example).

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Artificial recharge at spreading grounds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flow is generally from areas of recharge in the north and east along the edges the San Bernardino Mountains and the Crafton and Yucaipa Hills toward the southwest and west and the Bunker Hill-B management zone. The Yucaipa management zone is highly faulted into a number of groundwater subbasins (Eckis, 1934; Burnham and Dutcher, 1960; Dutcher and Fenzel, 1972). Groundwater flows downgradient from subbasin to subbasin as underflow across the faults bounding the subbasins. Discharge

· Groundwater production.

· Underflow to Bunker Hill-B and, possibly, San Timoteo management zones. Boundaries

· San Andreas Fault/San Bernardino Mountains to the north. The San Andreas is a major active fault zone and a known groundwater barrier. The southern-most lineament was chosen and mapped as the management zone boundary.

· Crafton Hills and Redlands Fault to the west. The Crafton Hills are an elevated ridge of impermeable bedrock separating the Bunker Hill-B and Yucaipa management zones. North of the Crafton Hills, the management zone boundary crosses a narrow fault trough between the Oak Glen Fault and the San Andreas Fault. Limited groundwater flow from the Yucaipa management zone may cross this boundary into Bunker Hill-B. South of the Crafton Hills, the boundary follows the Redlands Fault to the Banning Fault. The Redlands Fault is a known barrier to groundwater flow, but groundwater leakage occurs across this fault from the

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Yucaipa management zone into Bunker Hill-B (Burnham and Dutcher, 1960; Dutcher and Fenzel, 1972).

· Banning Fault to the south. The Banning Fault separates Yucaipa from the San Timoteo management zone. The Banning Fault is a major geologic feature along which large-scale movement has occurred. There also is evidence that the Banning Fault is a barrier to groundwater flow. Dutcher and Fenzel (1972) noted higher water levels in wells, on the order of 100-200 feet, on the north side of the fault along its western portion south and west of Reservoir Canyon Hill. Burnham and Dutcher (1960) noted its barrier effect where San Timoteo Canyon crosses the Banning Fault south of Redlands, in the Calimesa area, and north of Beaumont. Groundwater elevation contours in Figure 3-2 and 3-3 and in the literature suggest groundwater flow approximately parallel to the Banning Fault in its vicinity within the Yucaipa and San Timoteo management zones.

· Yucaipa Hills to the northwest. The Yucaipa Hills are an elevated ridge of impermeable bedrock separating the Yucaipa management zone from the northeastern-most portion of the San Timoteo management zone.

Management Zone: San Timoteo

Recharge

· Infiltration within the channels of streams overlying the management zone (Noble Creek, for example) and in San Timoteo Wash.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· In the northeastern portion of the San Timoteo management zone, groundwater recharged within the tributaries exiting the San Bernardino Mountains and Yucaipa Hills flows southward toward Banning Fault, which likely acts as a groundwater barrier. Underflow across the Banning Fault merges with groundwater underlying the Beaumont Plain and flows west within the sediments underlying San Timoteo Canyon. Discharge

· Groundwater production.

· Underflow to Bunker Hill-B and, possibly, Yucaipa management zones. Boundaries

· San Andreas Fault/San Bernardino Mountains/Yucaipa Hills in the northeast. The San Andreas is a major active fault zone and a known groundwater barrier. The southern-most lineament was chosen and mapped as the management zone boundary. The tributaries exiting the San Bernardino Mountains in this area are surrounded by impermeable bedrock of the Yucaipa Hills.

· Surface water drainage divide to the east. This boundary is drawn along a surface drainage divide that approximately coincides with a groundwater divide near the city of Beaumont. Surface water and groundwater water east of the boundary flows east toward the ; surface and groundwater west of the boundary flows west toward San Timoteo Canyon.

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· San Jacinto Fault and a surface water drainage divide to the south. The San Jacinto Fault is a known barrier to groundwater flow, and separates the San Timoteo from the Colton management zone in the upper reaches of Reche Canyon. Further south, the San Jacinto Fault has juxtaposed impermeable bedrock with the semi-permeable sediments of the San Timoteo Badlands. Further south, the San Timoteo management zone boundary follows a surface water drainage divide within the San Timoteo Badlands.

· Banning Fault and Bunker Hill-B to the north. The Banning Fault separates Yucaipa from the San Timoteo management zone. The Banning Fault is a major geologic feature along which large-scale movement has occurred. There also is evidence that the Banning Fault is a barrier to groundwater flow. Dutcher and Fenzel (1972) noted higher water levels in wells, on the order of 100-200 feet, on the north side of the fault along its western portion south and west of Reservoir Canyon Hill. Burnham and Dutcher (1960) noted its barrier effect where San Timoteo Canyon crosses the Banning Fault south of Redlands, in the Calimesa area, and north of Beaumont. Groundwater elevation contours in Figure 3-2 and 3-3 and in the literature suggest groundwater flow approximately parallel to the Banning Fault in its vicinity within the Yucaipa and San Timoteo management zones. At the termination of the Banning Fault into the Loma Linda Fault, the management zone boundary arbitrarily crosses a low- permeable portion of the San Timoteo Badlands to the San Jacinto Fault – separating the San Timoteo and the Bunker Hill-B management zones.

3.3.2 San Jacinto Basins

The San Jacinto groundwater basins lie within the alluvial-filled valleys carved into the elevated bedrock plateau of the Perris Block. Collectively, the basins are nearly surrounded by impermeable bedrock mountains and hills. Internally, island-like masses of granitic and metamorphic bedrock rise above the valley floor. The San Jacinto River is the main tributary draining this large basin. Sediments eroded from igneous and metamorphic rocks within the surrounding mountains and internal hills have filled the valleys to provide reservoirs for groundwater. The San Jacinto and Casa Loma fault zones are the major geologic features that bound and/or cross-cut the groundwater basins, and typically are effective barriers to groundwater flow.

Figure 3-5 is an equal elevation contour map of the effective base of the freshwater aquifers within the alluvial-filled valleys west of the Casa Loma Fault. The formations underlying this surface primarily consist of consolidated igneous and metamorphic rocks – similar to the rocks exposed in the surrounding hills (MacRostie and Dolcini, 1959; Biehler and Lee, 1993). Note the “channel-like” configuration of the subsurface bedrock underlying many of the valleys west of the Casa Loma Fault. This subsurface bedrock configuration likely is of erosional origin and has since been filled with alluvial sediments. Wells within the groundwater basins exist predominantly under water table conditions.

The area between the San Jacinto and Casa Loma faults is a deep, alluvial-filled graben of tectonic origin, and is referred to herein as the San Jacinto Graben. The effective base of the freshwater is known to be deep but has not been accurately determined and, hence, is left unmapped in Figure 3-5. The San Jacinto Graben consists of a forebay area in the southeast (where surface water recharge primarily occurs) and a pressure area in the northwest (where deep aquifers exist under confined conditions). Well logs indicate that the pressure area is underlain by a thick, alternating series of fine-grained sediments (clays and silts) and coarse-grained sediments (sands and gravels). The fine-grained sediments commonly act as confining layers.

East of the San Jacinto Fault and the San Jacinto Graben forebay area is a narrow groundwater basin that occupies San Jacinto Canyon.

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The primary streams within the watershed are the San Jacinto River, which drains out of the San Jacinto Mountains across the San Jacinto Graben and into the Lakeview area; Salt Creek, which drains across the Hemet, Winchester, and Menifee valley areas; and the tributaries which drain across the Moreno and Perris areas. Surface water in these streams is able to drain out of the San Jacinto River watershed into Railroad Canyon Reservoir, but there exists no natural outlet for groundwater.

Before pumping and artificial recharge began in this area, primary recharge to the groundwater reservoirs was from infiltration of stream flow exiting the San Jacinto Mountains and the surrounding and internal mountains and hills. In general, groundwater flow mimicked surface drainage patterns. From the forebay areas in the San Jacinto Graben – the primary area of recharge for the San Jacinto Basins – groundwater flowed northwest into the pressure aquifers of the San Jacinto Graben. Some groundwater leaked across the Casa Loma Fault to recharge groundwater reservoirs in the Hemet and Lakeview areas. From there, groundwater flowed to the west into the Menifee Valley and Perris areas, where it discharged as rising water in Salt Creek and the San Jacinto River. In the north, relatively minor recharge along the flanks of the surrounding hills flowed slowly south to commingle with groundwater flowing north in the San Jacinto Graben and with groundwater flowing west out of the Lakeview area (MacRostie and Dolcini, 1959; Ruchlewicz, 1978).

Groundwater production and artificial recharge has significantly modified the groundwater flow systems within much of the region – especially west of the Casa Loma Fault. This can be seen in Figures 3-6 and 3-7, which are groundwater elevation contour maps for Fall 1973 and Fall 1997, respectively. Note that groundwater flow paths (perpendicular to the contours) are different from the original flow system described above, and even are different from 1973 to 1997. For example, groundwater production in the Hemet area created a “pumping hole” which has reversed the original westward flow of groundwater (Figures 3-6 and 3-7). As another example, westward flow of groundwater in the Lakeview area that can still be seen in 1973 (Figure 3-6) has reversed in 1997 (Figure 3-7). This reversal in hydraulic gradient is the result of groundwater overdraft in the Lakeview area and artificial recharge and returns from agricultural use in the Perris area (Boyle and Geoscience, 1997).

In contrast, groundwater flow directions within the San Jacinto Graben generally have been stable over time due to relatively consistent and abundant recharge along the San Jacinto River as it exits the San Jacinto Mountains. However, groundwater production has, in part, significantly lowered groundwater elevations compared to pre-pumping conditions within the San Jacinto Graben, and has locally altered flow directions.

The reversals in hydraulic gradient within the groundwater reservoirs west of the Casa Loma Fault are, in part, likely a result of the physical configuration of these groundwater basins (see Figure 3-5). Topographic differences across a basin typically create a hydraulic gradient within the underlying groundwater reservoir; however, the topography within the alluvial-filled valleys west of the Casa Loma Fault is relatively flat. In addition, these alluvial-filled valleys are relatively shallow and narrow and, hence, total groundwater storage is small relative to changes in storage. A small storage change (say, caused by groundwater overdraft) in a portion of a small groundwater reservoir, such as Lakeview, can change groundwater levels more readily than a small storage change in a large groundwater reservoir, such as Chino Basin.

The inconsistent nature of flow systems within the groundwater reservoirs west of the Casa Loma Fault – primarily due to groundwater production and artificial recharge – provided challenges in the determination of management zone boundaries. As a result, groundwater flow across some management zone boundaries will occur to varying degrees and may vary in magnitude and direction over time. These details will be discussed below. Nevertheless, nine management zones were delineated based on major

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impermeable boundaries, constrictions in impermeable bedrock, groundwater divides, and internal flow systems (Figure 3-8):

· Canyon

· San Jacinto Upper Graben

· San Jacinto Lower Graben

· Hemet North

· Hemet South

· Lakeview

· Perris North

· Perris South

· Menifee

Management Zone: Canyon

Recharge

· Infiltration of flow within the channels of the San Jacinto River, Poppet Creek and Indian Creek as they exit the San Jacinto Mountains.

· Infiltration of flow within other unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Artificial recharge of native waters at spreading grounds along the San Jacinto River.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· West toward the San Jacinto Fault. Discharge

· Groundwater production.

· Underflow across the San Jacinto Fault to the Upper San Jacinto Graben management zone. Boundaries

· San Jacinto Mountains. The San Jacinto Mountains are composed of consolidated crystalline bedrock and semi-consolidated sedimentary rocks. These rocks are virtually impermeable and bound the water-bearing, alluvial-filled canyons within this management zone.

· San Jacinto Fault to the west. The San Jacinto Fault is an active fault zone and typically is a competent barrier to groundwater flow. A branch of the extends southeast approximately along the channel of Bautista Creek until it intersects the Park Hill Fault. Groundwater elevations typically are about 200 feet higher on the east side of the fault (within the Canyon management zone). In the early 1900s, the barrier effect of the fault

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resulted in rising groundwater within the San Jacinto River upstream of the fault. This area was known as the Cienega (MacRostie and Dolcini, 1959).

Management Zone: Upper San Jacinto Graben

Recharge

· Infiltration of flow within channel of the San Jacinto River and, to a lesser degree, Bautista Creek overlying the forebay area.

· Infiltration of flow within other unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Artificial recharge of imported, native, and recycled water at spreading grounds, wastewater percolation ponds, and reservoirs.

· Intermittent underflow from the Lower San Jacinto Graben within the pressure aquifers.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Generally, groundwater flows from the forebay area in the southeast into the pressure aquifers in the northwest. Specific yield investigations reveal a northwest trending belt of highly permeable sediments from the forebay area into the pressure area, enhancing the northwestward flow of groundwater.

· Figures 3-6 and 3-7 show some modification of the prevailing flow system by groundwater production. Discharge

· Groundwater production.

· Underflow to the Lower San Jacinto Graben management zone within the pressure aquifers.

· Underflow across the Casa Loma Fault to the Hemet South, Hemet North, and Lakeview management zones. Boundaries

· San Jacinto Fault to the northeast. The San Jacinto Fault is a known barrier to groundwater flow, and separates the San Jacinto Graben from the San Timoteo Badlands and the San Jacinto Mountains. East of the City of San Jacinto, a branch of San Jacinto Fault Zone cuts the alluvial fill by extending southeast across the San Jacinto River and approximately along the channel of Bautista Creek until it intersects the Park Hill Fault. This branch of the San Jacinto Fault Zone separates the Upper San Jacinto Graben from the Canyon management zone. Groundwater elevations typically are about 200 feet higher on the east side of the fault (within the Canyon management zone). In the early 1900s, the barrier effect of the fault resulted in rising groundwater within the San Jacinto River upstream of the fault. This area was known as the Cienega (MacRostie and Dolcini, 1959).

· Casa Loma and Bautista Creek fault zones to the southwest. The Casa Loma and Bautista Creek fault zones are known barriers to groundwater flow as evidenced by (1) differences in groundwater elevation time histories of wells on opposite sides of the fault zones, (2) differences in groundwater elevations in wells on opposite sides of the fault zones, and (3) the

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existence of intermittent springs along the Casa Loma Fault in the vicinity of Casa Loma Hill (MacRostie and Dolcini, 1959). However, groundwater leaks across the fault zones as underflow to the Hemet South, Hemet North, and Lakeview management zones (MacRostie and Dolcini, 1959; Ruchlewicz, 1978; Williams et al., 1993).

· Flow system boundary with the Lower San Jacinto Graben management zone to the northwest. Comparison of groundwater level contour maps over time demonstrates a distinction between the flow systems of Upper and Lower San Jacinto Graben management zones (Figures 3-6 and 3-7). In the vicinity of Mystic Lake, groundwater flowing northwest and west in the Upper San Jacinto Graben begins to flow southwest toward the Casa Loma Fault. In this same area, groundwater flowing south in the Lower San Jacinto Graben also begins to flow southwest, probably commingling with groundwater in the Upper San Jacinto Graben. The management zone boundary that separates these flow systems is approximately parallel to groundwater flow directions and runs from the San Jacinto Fault Zone to the Casa Loma Fault. Groundwater discharges in the area as either groundwater production, rising water along the Casa Loma Fault, or underflow across the Casa Loma Fault to the Hemet North and Lakeview management zones (MacRostie and Dolcini, 1959; Schlehuber et al., 1989; Williams et al., 1993).

Management Zone: Lower San Jacinto Graben

Recharge

· Infiltration of flow within the unlined channels of streams overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Intermittent underflow from the Upper San Jacinto Graben within the pressure aquifers.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Generally, groundwater flows from forebay areas in the north into the pressure aquifers in the southeast. Discharge

· Groundwater production.

· Underflow to the Upper San Jacinto Graben management zone within the pressure aquifers.

· Underflow across the Casa Loma Fault to the Lakeview management zone. Boundaries

· San Jacinto Fault to the northeast. The San Jacinto Fault is a known barrier to groundwater flow, and separates the San Jacinto Graben from the San Timoteo Badlands and the San Jacinto Mountains.

· Casa Loma Fault and its northwestward extension. The Casa Loma Fault is a known barriers to groundwater flow as evidenced by (1) differences in groundwater elevation time histories of wells on opposite sides of the fault zones, (2) differences in groundwater elevations in wells on opposite sides of the fault zones, and (3) the existence of intermittent springs along the Casa Loma Fault in the vicinity of Casa Loma Hill. However, it is believed that the barrier effect diminishes to the northwest of Casa Loma Hill and that groundwater

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leaks across the fault zone as underflow to the Lakeview management zone (MacRostie and Dolcini, 1959; Schlehuber et al., 1989; Williams et al., 1993). Little well data exist to support the extension of the fault northwest of the Mount Russell Range, but the California Division of Mines and Geology has mapped the fault from Mount Russell to the northwest into Reche Canyon (Rogers, 1965). In addition, the effective base of the aquifer deepens northeast of the fault in this area (B. Mortazavi, pers. comm., 1999). These lines of evidence are the basis for alignment of the management zone boundary along the northwestward extension of the fault. However, some authors have suggested that groundwater flows from the northern portions of the Upper San Jacinto Graben across the Casa Loma Fault into the North Perris management zone (Schlehuber et al., 1989).

· Various crystalline bedrock outcrops to the north and west. Impermeable, crystalline bedrock outcrops that compose the Bernasconi Hills/Mount Russell Range to the west and the hills between the San Jacinto and Casa Loma fault zones to the north are hard rock barriers to groundwater flow.

· Flow system boundary with the Upper San Jacinto Graben management zone to the southeast. Comparison of groundwater level contour maps over time demonstrates a distinction between the flow systems of Upper and Lower San Jacinto Graben management zones (Figures 3-6 and 3-7). In the vicinity of Mystic Lake, groundwater flowing northwest and west in the Upper San Jacinto Graben begins to flow southwest toward the Casa Loma Fault. In this same area, groundwater flowing south in the Lower San Jacinto Graben also begins to flow southwest, probably commingling with groundwater in the Upper San Jacinto Graben. The management zone boundary that separates these flow systems is approximately parallel to groundwater flow directions and runs from the San Jacinto Fault Zone to the Casa Loma Fault. Groundwater discharges in the area as either groundwater production, rising water along the Casa Loma Fault, or underflow across the Casa Loma Fault to the Hemet North and Lakeview management zones (MacRostie and Dolcini, 1959; Schlehuber et al., 1989; Williams et al., 1993).

Management Zone: South Hemet

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Underflow across the Bautista Creek and Casa Loma fault zones from the Upper San Jacinto Graben management zone.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater elevation contour maps (Figures 3-6 and 3-7) indicate that groundwater flow is from the surrounding management zone boundaries inward toward the City of Hemet. As previously described, this flow system differs from original flow conditions (westward from the Casa Loma Fault into the Winchester area) due to prolonged pumping from aquifers beneath the City of Hemet. Discharge

· Groundwater production.

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Boundaries

· Casa Loma and Bautista Creek fault zones to the east. The Casa Loma and Bautista Creek fault zones are known barriers to groundwater flow as evidenced by (1) differences in groundwater elevation time histories of wells on opposite sides of the fault zones, (2) differences in groundwater elevations in wells on opposite sides of the fault zones, and (3) the existence of intermittent springs along the Casa Loma Fault in the vicinity of Casa Loma Hill (MacRostie and Dolcini, 1959). However, groundwater leaks across the fault zones as underflow from the Upper San Jacinto management zone (MacRostie and Dolcini, 1959; Ruchlewicz, 1978; Williams et al., 1993).

· Groundwater divide near Esplanade Avenue to the north. A groundwater high located between the Casa Loma Fault and the Lakeview Mountains near Esplanade Avenue is apparent in the groundwater elevation contours maps of Figures 3-6 and 3-7, as well as being indicated in the literature (MacRostie and Dolcini, 1959; Williams et al., 1993; Rees et al., 1993).

· Groundwater divide in Winchester area to the west. A groundwater high in the Winchester area near Highway 79 is apparent in the groundwater elevation contours map of Figure 3-7 (Fall, 1997), as well as being indicated in the literature (Burton et al., 1996; Kaehler et al., 1998). This groundwater divide did not exist under original flow conditions (groundwater flowed to the west through the Winchester area), but has existed, in some form, since prior to 1935 (Kaehler et al., 1998). The divide is likely an artifact of natural and artificial recharge and groundwater production patterns. As such, the position (or the very existence) of this groundwater divide may vary with changing artificial recharge and/or production patterns.

· Various crystalline bedrock outcrops to the north and south. Impermeable, crystalline bedrock outcrops that compose the Lakeview Mountains to the north and the hills surrounding the Domenigoni and Diamond valleys to the south are hard rock barriers to groundwater flow.

Management Zone: North Hemet

Recharge

· Infiltration of flow within unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the Lakeview Mountains.

· Underflow across the Casa Loma fault zone from the Upper San Jacinto Graben management zone.

· Artificial recharge of recycled water at the Hemet-San Jacinto Wetlands/Regional Water Reclamation Facility.

· Underflow through a narrow gap between the Lakeview Mountains and the Casa Loma Fault from the Lakeview management zone. This source of recharge is not supported by groundwater elevation contour maps (Figures 3-6 and 3-7), but was described by EMWD as a recent occurrence due to groundwater production in North Hemet management zone (P. Ravishanker, pers. comm., 1999).

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater elevation contour maps (Figures 3-6 and 3-7) and descriptions of groundwater flow systems in the literature indicate (MacRostie and Dolcini, 1959; Rees et al., 1993) the existence of a groundwater divide located between the Casa Loma Fault and the Lakeview

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Mountains near Esplanade Avenue. Groundwater north of this divide flows northwest through a narrow gap between the Lakeview Mountains and the Casa Loma Fault and into the Lakeview management zone. However, recent groundwater level data suggest that flow direction has reversed in this area and now exits the Lakeview management zone into Hemet North (P. Ravishanker, pers. comm., 1999). Discharge

· Groundwater production.

· Underflow through a narrow gap between the Lakeview Mountains and the Casa Loma Fault into the Lakeview management zone. Boundaries

· Casa Loma fault zone to the east. The Casa Loma fault zone is a known barrier to groundwater flow as evidenced by (1) differences in groundwater elevation time histories of wells on opposite sides of the fault zones, (2) differences in groundwater elevations in wells on opposite sides of the fault zones, and (3) the existence of intermittent springs along the Casa Loma Fault in the vicinity of Casa Loma Hill (MacRostie and Dolcini, 1959). However, groundwater leaks across the fault zones as underflow from the Upper San Jacinto management zone (MacRostie and Dolcini, 1959; Ruchlewicz, 1978; Williams et al., 1993).

· Groundwater divide near Esplanade Avenue to the south. A groundwater high located between the Casa Loma Fault and the Lakeview Mountains near Esplanade Avenue is apparent in the groundwater elevation contours maps of Figures 3-6 and 3-7, as well as being indicated in the literature (MacRostie and Dolcini, 1959; Williams et al., 1993; Rees et al., 1993).

· Lakeview Mountains to the west. Impermeable, crystalline bedrock outcrops that compose the Lakeview Mountains to the west are hard rock barriers to groundwater flow.

· Lakeview management zone to the north. To the north, the gap between the Lakeview Mountains and the Casa Loma Fault becomes narrow. This area of constriction in the water- bearing alluvium is the boundary between the Hemet North and Lakeview management zones.

Management Zone: Lakeview

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills (Bernasconi Hills and the Lakeview Mountains).

· Underflow across the Casa Loma fault zone from the Upper and Lower San Jacinto Graben management zones.

· Underflow through a narrow gap between the Lakeview Mountains and the Casa Loma Fault from the Hemet North management zone.

· Underflow through a bedrock constriction from the Perris South management zone.

· Deep percolation of precipitation and returns from use.

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Groundwater Flow

· Under original conditions, groundwater flow followed the surface drainage pattern of the San Jacinto River: across the Casa Loma Fault Zone, westward through the Lakeview basin, and through a bedrock constriction into the Perris area. Artificial recharge and groundwater production has significantly modified groundwater flow conditions. Groundwater now flows from the Perris area northeastward into the Lakeview basin toward a “pumping depression” in the groundwater table (Figure 3-7).

· Groundwater recharged along the flanks of the Bernasconi Hills and the Lakeview Mountains flows toward the center of the basin.

· Groundwater exiting Hemet North and entering the Lakeview management zone continues northward toward the “pumping depression.” However, recent groundwater level data suggest that flow direction has reversed in this area and now exits the Lakeview management zone into Hemet North (P. Ravishanker, pers. comm., 1999). Discharge

· Groundwater production.

· Underflow through a narrow gap between the Lakeview Mountains and the Casa Loma Fault into the Hemet North management zone. This discharge term is not supported by groundwater elevation contour maps (Figures 3-6 and 3-7), but was described by EMWD as a recent occurrence due to groundwater production in North Hemet management zone (P. Ravishanker, pers. comm., 1999). Boundaries

· Casa Loma fault zone to the east. The Casa Loma fault zone is a known barrier to groundwater flow as evidenced by (1) differences in groundwater elevation time histories of wells on opposite sides of the fault zones, (2) differences in groundwater elevations in wells on opposite sides of the fault zones, and (3) the existence of intermittent springs along the Casa Loma Fault in the vicinity of Casa Loma Hill (MacRostie and Dolcini, 1959). Where the fault zone separates the San Jacinto Graben from the Lakeview basin, artesian pressures originally were present within the San Jacinto Graben but where not present within the Lakeview basin, indicating the barrier effect of the fault. In addition, water quality is significantly different in wells on opposite sides of the fault (Boyle and Geoscience, 1997). The western branch of the fault zone, the Bridge Street Fault, coincides with the management zone boundary. However, groundwater may leak across the fault zone as underflow when piezometric heads are higher within the aquifers of the Upper and Lower San Jacinto Graben management zones (MacRostie and Dolcini, 1959; Ruchlewicz, 1978; Williams et al., 1993).

· Hemet North management zone to the east. To the east, the gap between the Lakeview Mountains and the Casa Loma Fault becomes narrow. This area of constriction in the water- bearing alluvium is the boundary between the Hemet North and Lakeview management zones.

· Bernasconi Hills and Lakeview Mountains to the north and south, respectively. Impermeable, crystalline bedrock outcrops that compose the Bernasconi Hills and the Lakeview Mountains to the north and south, respectively, are hard rock barriers to groundwater flow.

· Bedrock constriction/saddle to the west. To the west, the gap between the Bernasconi Hills and the Lakeview Mountains becomes narrow and the buried bedrock surface forms a saddle (Figure 3-5). This area of constriction in the water-bearing alluvium is the boundary between the Perris South and Lakeview management zones.

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Management Zone: Perris South

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Underflow from a groundwater high in the Winchester area.

· Intermittent underflow from the Perris North management zone through a broad bedrock gap.

· Artificial recharge of recycled water at various storage/percolation ponds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· From areas of recharge in the south (Winchester, Sun City, and Homeland regions), groundwater flow is generally to the north into the Perris area. Locally, groundwater flow directions are more complex due to artificial recharge and production patterns, but the general flow direction to the north is prevalent. Discharge

· Groundwater production.

· Underflow through a bedrock constriction into the Lakeview management zone.

· Intermittent underflow through a broad bedrock gap into the Perris North management zone.

· Underflow through a narrow bedrock constriction from the Winchester area into the Menifee management zone.

· Underflow through a bedrock constriction/saddle from the Sun City area into the Menifee management zone. Boundaries

· Groundwater divide in Winchester area. A groundwater high in the Winchester area near Highway 79 is apparent in the groundwater elevation contours map of Figure 3-7 (Fall, 1997), as well as being indicated in the literature (Burton et al., 1996; Kaehler et al., 1998). This groundwater divide did not exist under original flow conditions (groundwater flowed to the west from the Hemet area through the Winchester area), but has existed, in some form, since prior to 1935 (Kaehler et al., 1998). The divide is likely an artifact of natural and artificial recharge and groundwater production patterns. As such, the position (or the very existence) of this groundwater divide may vary with changing artificial recharge and/or production patterns.

· Bedrock constrictions/saddles bordering the Menifee management zone. Southwest of Winchester Ponds, a narrow constriction in the bedrock coincides with a buried bedrock saddle surface (Figure 3-5). This area of constriction in the water-bearing alluvium is a boundary between the Perris South and Menifee management zones. Groundwater can flow through this bedrock gap from the Winchester area into the Menifee management zone – especially during times of high groundwater levels. Southeast of Sun City, a similar narrow constriction in the bedrock coincides with a buried bedrock saddle surface (Figure 3-5). This area of constriction in the water-bearing alluvium also is a boundary between the Perris South and Menifee management zones. Groundwater flows through this bedrock gap from the Sun City area into the Menifee management zone.

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Analysis of groundwater level time histories indicates higher groundwater elevations in the Perris South management zone as compared to groundwater elevations in the Menifee management zone. Flow through these bedrock gaps has been documented to occur from Perris South to Menifee, but flow in the opposite direction, while theoretically possible, is indicated by analysis of historical groundwater elevations or the literature (Burton et al., 1996; Kaehler et al., 1998).

· Bedrock constriction/saddle bordering the Lakeview management zone. To the northeast, the gap between the Bernasconi Hills and the Lakeview Mountains becomes narrow and the buried bedrock surface forms a saddle (Figure 3-5). This area of constriction in the water- bearing alluvium is the boundary between the Perris South and Lakeview management zones. Under original flow conditions, groundwater flowed westward from Lakeview into Perris South. However, artificial recharge and groundwater production has significantly modified groundwater flow conditions. Groundwater now flows from Perris South eastward into Lakeview toward a “pumping depression” in the groundwater table (Figure 3-7).

· Bedrock constriction bordering the Perris North management zone. North of the San Jacinto River in the Perris area, the gap between the Bernasconi Hills and the bedrock hills to the west narrows (Figure 3-5). This area of constriction in the water-bearing alluvium is a boundary between the Perris South and the Perris North management zones. While groundwater is capable of flowing in either direction across this boundary, analyses of groundwater level contours maps generated for this study (Figure 3-6 and 3-7) and in the literature (Burton et al., 1996) indicate little flow across this boundary. Descriptions of original flow conditions suggested limited groundwater flow from the Sunnymead/Moreno area exited as rising water in the San Jacinto River in the Perris area. However, Figure 3-6 shows a broad depression in the groundwater table in the vicinity of the San Jacinto River during Fall, 1973 – probably induced by groundwater production – indicating little groundwater flow across the proposed boundary. The groundwater elevation contours in Figure 3-7 indicate groundwater flow parallel to this boundary, also suggesting little groundwater flow across this boundary. It is apparent from past and present groundwater level maps that hydraulic gradients within this area, which have been induced by natural and artificial phenomena, are such that little groundwater flow crosses this boundary in either direction.

· Surrounding bedrock mountains and hills. Impermeable, crystalline bedrock outcrops that compose the surrounding mountains and hills are hard rock barriers to groundwater flow.

Management Zone: Perris North

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Potential underflow from the Lower San Jacinto Graben management zone in the northeast.

· Intermittent underflow through a broad bedrock gap from the Perris South management zone.

· Underflow from leakage beneath the Dam.

· Artificial recharge of recycled water in storage/percolation ponds at the Moreno Valley Reclaimed Water Reclamation Facility.

· Deep percolation of precipitation and returns from use.

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Groundwater Flow

· From areas of recharge along the flanks of the surrounding hills, groundwater flows towards the deeper center of the alluvial-filled valley. The general flow direction within the center of the valley is from the north (Sunnymead, Moreno, and Lake Perris regions) to the south towards the Perris area. Locally, groundwater flow directions are more complex due to artificial recharge and production patterns, but the general flow direction to the south is prevalent. Discharge

· Groundwater production.

· Intermittent underflow through a broad bedrock gap into the Perris South management zone. Boundaries

· Bedrock constriction bordering the Perris South management zone. North of the San Jacinto River in the Perris area, the gap between the Bernasconi Hills and the bedrock hills to the west narrows (Figure 3-5). This area of constriction in the water-bearing alluvium is a boundary between the Perris South and the Perris North management zones. While groundwater is capable of flowing in either direction across this boundary, analysis of groundwater level contours maps generated for this study (Figure 3-6 and 3-7) and in the literature (Burton et al., 1996) indicate little flow across this boundary. Descriptions of original flow conditions suggested limited groundwater flow from the Sunnymead/Moreno area exited as rising water in the San Jacinto River in the Perris area. However, Figure 3-6 shows a broad depression in the groundwater table in the vicinity of the San Jacinto River during Fall, 1973 – probably induced by groundwater production – indicating little groundwater flow across the proposed boundary. The groundwater elevation contours in Figure 3-7 indicate groundwater flow parallel to this boundary, also suggesting little groundwater flow across this boundary. It is apparent from past and present groundwater level maps that hydraulic gradients within this area, which have been induced by natural and artificial phenomena, are such that little groundwater flow crosses this boundary in either direction.

· Surrounding bedrock mountains and hills. Impermeable, crystalline bedrock outcrops that compose the surrounding mountains and hills are hard rock barriers to groundwater flow.

· Perris Lake Dam to the east. Perris Dam extends across an alluvial-filled valley located between the Mount Russell Range and the Bernasconi Hills. The dam is the management zone boundary in this area. Water impounded behind Perris Dam seeps beneath the dam and enters the Perris North management zone as underflow (EMWD, 1998).

· Northwestward extension of the Casa Loma Fault. The Casa Loma Fault is a known barrier to groundwater flow. However, it is believed that the barrier effect diminishes to the northwest (MacRostie and Dolcini, 1959). Little well data exist to support the extension of the fault northwest of the Mount Russell Range, but the California Division of Mines and Geology has mapped the fault from Mount Russell to the northwest into Reche Canyon (Rogers, 1965). In addition, the effective base of the aquifer deepens northeast of the fault in this area (B. Mortazavi, pers. comm., 1999). These lines of evidence are the basis for alignment of the management zone boundary along the northwestward extension of the fault. However, some authors have suggested that groundwater flows from the northern portions of the Upper San Jacinto Graben across the Casa Loma Fault into the North Perris management zone (Schlehuber et al., 1989).

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Management Zone: Menifee

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Underflow through a narrow bedrock constriction from the Winchester area.

· Underflow through a bedrock constriction/saddle from the Sun City area.

· Artificial recharge of recycled water in storage/percolation ponds at the Sun City Reclaimed Water Reclamation Facility (currently unused).

· Deep percolation of precipitation and returns from use. Groundwater Flow

· From areas of recharge along the flanks of the surrounding hills and from the sources of underflow at bedrock gaps, groundwater flows towards the deeper center of the alluvial-filled valley and, thence, southeast towards the Domenigoni Valley. Discharge

· Groundwater production.

· Intermittent underflow through a bedrock gap into the Domenigoni Valley. Boundaries

· Bedrock constrictions/saddles bordering the Perris South management zone. Southwest of Winchester Ponds, a narrow constriction in the bedrock coincides with a buried bedrock saddle surface (Figure 3-5). This area of constriction in the water-bearing alluvium is a boundary between the Perris South and Menifee management zones. Groundwater can flow through this bedrock gap from the Winchester area into the Menifee management zone – especially during times of high groundwater levels. Southeast of Sun City, a similar narrow constriction in the bedrock coincides with a buried bedrock saddle surface (Figure 3-5). This area of constriction in the water-bearing alluvium also is a boundary between the Perris South and Menifee management zones. Groundwater flows through this bedrock gap from the Sun City area into the Menifee management zone. Analysis of groundwater level time histories indicates higher groundwater elevations in the Perris South management zone as compared to groundwater elevations in the Menifee management zone. Flow through these bedrock gaps has been documented to occur from Perris South to Menifee, but flow in the opposite direction, while theoretically possible, is indicated by analysis of historical groundwater elevations or the literature (Burton et al., 1996; Kaehler et al., 1998).

· Bedrock constriction to the east. A narrow constriction in the bedrock coincides with a surface water drainage divide (Figure 3-5). This area of constriction in the water-bearing alluvium is a boundary between the Menifee management zones and the Domenigoni Valley. Limited groundwater flow occurs in either direction through this bedrock depending on prevailing recharge and/or production patterns.

· Surrounding bedrock mountains and hills. Impermeable, crystalline bedrock outcrops that compose the surrounding mountains and hills are hard rock barriers to groundwater flow.

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3.3.3 Chino – Rialto/Colton – Riverside Basins

The Chino, Rialto-Colton, and Riverside groundwater basins are part of a larger, broad, alluvial-filled basin located between the San Gabriel/San Bernardino Mountains to the north and the elevated Perris Block/San Jacinto Mountains to the south. The Santa Ana River is the main tributary draining the basin. Sediments eroded from igneous and metamorphic rocks within the surrounding mountains have filled this basin to provide reservoirs for groundwater. The San Jacinto Fault cuts through this alluvial-filled basin from the northwest to the southeast to form a major barrier to groundwater flow and, hence, separates the groundwater basins of the San Bernardino Valley and Yucaipa/Beaumont Plains in the east from the groundwater basins of the Chino, Rialto-Colton, and Riverside areas in the west.

In general, the Chino, Rialto-Colton, and Riverside basins are bounded by the San Gabriel Mountains in the north, the Chino/Puente Hills to the west, the elevated bedrock hills of the Perris Block to the south, and the San Jacinto Fault to the east. Figure 3-9 is an equal elevation contour map of the effective base of the freshwater aquifers in this region. Note that numerous faults and bedrock protrusions sub-divide the larger area into numerous groundwater subbasins with unique bedrock configurations. The most prominent features of the base of the freshwater include the deep trough within the central region (Chino Basin) and the relatively shallow, irregular configuration in the present-day region of the Santa Ana River (Riverside Basins).

The major internal faults within this area – the Rialto-Colton Fault, the Red Hill Fault, and the San Jose Fault – are known barriers to groundwater flow. These faults, their effects on groundwater movement, and groundwater movement in general have been studied in detail by various entities and authors (Eckis, 1934; Gleason, 1947; Burnham, 1953; MacRostie and Dolcini, 1959; Dutcher & Garrett, 1963; DWR, 1965a; Gosling, 1966; DWR, 1970; Woofenden and Kadhim, 1997) and will be discussed below.

Groundwater within the Rialto-Colton and Riverside basins primarily exists under unconfined to semi- confined conditions. Historically, however, the southwestern portion of the Chino Basin was an area of flowing wells – indicating the presence of fine-grained, confining sedimentary layers at depth (Fife et al., 1976). A three-layer representation of the water-bearing and confining sedimentary units within the Chino Basin was developed for Chino Basin Water Resources Management Study (Montgomery et al., 1994). This layer geometry was used for our calculations of ambient water quality within a portion of the Chino Basin (described in Section 4).

Predominant recharge to the groundwater reservoirs in the area is from percolation of direct precipitation and infiltration of stream flow within tributaries exiting the surrounding mountains and hills and within the Santa Ana River. In general, groundwater flow mimics surface drainage patterns: from the areas of high elevation towards areas of discharge near the Santa Ana River and at Prado Flood Control Basin. Figures 3-10 and 3-11 are groundwater elevation contour maps for Fall 1973 and Fall 1997 that show this general groundwater flow pattern. Comparing these two contour maps, note that groundwater flow paths (perpendicular to the contours) are generally similar. Groundwater elevation contour maps from other periods (either from the literature or constructed for this study) also show similar flow paths, indicating consistent flow systems within this area.

Also note in Figures 3-10 and 3-11 three general flow systems:

· within the Chino Basin, where groundwater flows south and southwestward from areas of recharge in the north and east (areas flanking the San Gabriel and ) to converge low in the basin and discharge as rising water within Prado Basin;

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· within the Rialto-Colton Basin, located between the San Jacinto and Rialto-Colton faults, where groundwater flows from areas of recharge near mountain fronts in the north and south toward discharge areas near the Santa Ana River; and

· within the Riverside Basins, where groundwater flows from areas of recharge along the flanks of the surrounding hills to converge beneath the Santa Ana River until discharging as rising water at the Riverside Narrows. The three flow systems described above can be further sub-divided into hydrologically-distinct management zones if internal flow systems are shown to be consistent over time. We have delineated fourteen management zones within the Chino, Rialto-Colton, and Riverside basins based on major impermeable boundaries, groundwater divides, and internal flow systems (Figure 3-12):

· Cucamonga

· Chino-1 through Chino-5

· Rialto

· Colton

· Riverside-A through Riverside-F

Management Zone: Cucamonga

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the San Gabriel Mountains.

· Artificial recharge of storm flow at spreading grounds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flow generally is southward from areas of recharge in the north towards the Red Hill Fault in the south. Groundwater flow in the eastern part of the basin is less well-defined, but is believed to flow south towards the Red Hill fault and then southwest along the Red Hill Fault. Discharge

· Groundwater production.

· Underflow as seepage across the Red Hill Fault to Chino-1 and Chino-2 management zones.

· Rising water within Cucamonga Creek when groundwater elevations are high. Boundaries

· Cucamonga Fault Zone/San Gabriel Mountains to the north. The Cucamonga Fault is a major, active fault zone, and is in part responsible for uplift of the San Gabriel Mountains, which are composed of impermeable metamorphic and igneous bedrock. The management zone boundary was mapped along the mountain front at the contact between the impermeable bedrock and the water-bearing alluvium.

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· Red Hill Fault to the south. The Red Hill Fault is a recently active fault evidenced by recognizable fault scarps such as Red Hill at the extreme southern extent of the fault near Foothill Boulevard. The fault is a known barrier to groundwater flow and groundwater elevation differences on the order of several hundred feet on opposite sides of the fault are typical (Eckis, 1934; DWR, 1970). Groundwater seeps across the Red Hill Fault as underflow to the Chino-1 and Chino-2 management zones, especially during periods of high groundwater elevations within the Cucamonga management zone.

Management Zone: Chino-1

Recharge

· Infiltration of flow (and, locally, imported water) within unlined stream channels overlying the management zone.

· Underflow from the saturated sediments and fractures within the Puente/Chino Hills.

· Artificial recharge at spreading grounds of storm water, imported water, and water released from San Antonio Dam that is not recharged at spreading grounds operated by Pomona Valley Protective Agency.

· Underflow from seepage across the Red Hill Fault (from Cucamonga management zone) and the San Jose Fault (from the Claremont Heights and Pomona basins).

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flow generally is southward from areas of recharge in the north towards Prado Basin and the Santa Ana River in the south. Localized groundwater production has modified the general southward flow direction in parts of the management zone – especially in the Pomona and Montclair areas, where groundwater flows toward a broad depression in the groundwater table (see Figures 3-10 and 3-11). The Central Avenue Fault trends northwest beneath the west side of Chino-1. Groundwater elevation data analyzed for this study and reports from well driller’s (M. Roberts, 1999) indicate that while the Central Avenue Fault offsets bedrock, it does not impede the flow of groundwater. Discharge

· Groundwater production.

· Rising water within Chino Creek and within Prado Basin near the Santa Ana River.

· Evapotranspiration within Prado Basin where groundwater is near or at the ground surface. Boundaries

· Red Hill Fault to the northeast. The Red Hill Fault is a recently active fault evidenced by recognizable fault scarps such as Red Hill at the extreme southern extent of the fault near Foothill Boulevard. The fault is a known barrier to groundwater flow and groundwater elevation differences on the order of several hundred feet on opposite sides of the fault are typical (Eckis, 1934; DWR, 1970). Groundwater seeps across the Red Hill Fault as underflow to the Chino-1 and Chino-2 management zones, especially during periods of high groundwater elevations within the Cucamonga management zone.

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· San Jose Fault to the northwest. The San Jose Fault is known as an effective barrier to groundwater flow with groundwater elevation differences on the order of several hundred feet on opposite sides of the fault (Eckis, 1934; DWR, 1970). Groundwater seeps across the San Jose Fault as underflow to the Chino-1 management zone, especially during periods of high groundwater elevations within the Pomona and Claremont Heights management zones.

· Groundwater divide to the west. A natural groundwater divide separates the Chino-1 management zone from the Spadra Basin in the west. The divide, which extends from the eastern tip of the San Jose Hills southward to the Puente Hills, is produced by groundwater seepage from the Pomona Basin across the southern portion of the San Jose Fault (Eckis, 1934).

· Puente Hills/Chino Hills to the southwest. The Chino Fault extends from the northwest to the southeast along the western boundary of the Chino Basin. It is, in part, responsible for uplift of the Puente Hills and Chino Hills, which form a continuous belt of low hills west of the fault. The Chino and Puente Hills, primarily composed of consolidated sedimentary rocks, form an impermeable barrier to groundwater flow within the Chino-1 management zone.

· Prado Flood Control Basin to the south. Similar to the other management zones within the Chino Basin, Chino-1 pinches out to the south as groundwater is consumed by production and/or rises to become surface water in Chino Creek, the Santa Ana River, or Prado Basin.

· Flow system boundary with Chino-2 to the east. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within Chino- 1 and Chino-2 management zones. Figures 3-10 and 3-11 are two such maps that show areas of recharge located in the northern portions of Chino-1 and Chino-2 are distinct and spatially separated, in part, by the Cucamonga management zone. Water recharged in the northern portion of Chino-1 generally flows south (and, locally, to the west as a result of groundwater production patterns) staying southwest of the Cucamonga management zone. Water recharged in the northern portion of Chino-2 flows to the southwest, staying southeast of the Cucamonga management zone. Where these two flow systems meet, south of the Cucamonga management zone, groundwater flow directions are approximately parallel to each other. As groundwater flow continues south, the groundwater elevation contours suggest little, if any, cross-flow between flow systems. Nearing the southwestern (lowest) portion of the basin, these two flows systems become less distinct as all groundwater flow within Chino Basin converges and rises beneath Prado Basin. By analyzing groundwater elevation contours over a time, the management zone boundary that separates these consistent flow systems was drawn approximately parallel to groundwater flow direction from the point where the flow systems meet to discharge areas within Prado Basin.

Management Zone: Chino-2

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Artificial recharge at spreading grounds of storm water and imported water.

· Underflow from seepage across the Red Hill Fault (from Cucamonga management zone) and the northwest extension of the Rialto-Colton Fault (from the Rialto management zone).

· Deep percolation of precipitation and returns from use.

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Groundwater Flow

· Groundwater flow generally is southwestward from areas of recharge in the northeast towards Prado Basin in the southwest. Localized groundwater production has modified the general southwestward flow direction in parts of the management zone (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Rising water within Prado Basin.

· Evapotranspiration within Prado Basin where groundwater is near or at the ground surface. Boundaries

· Red Hill Fault to the northeast. The Red Hill Fault is a recently active fault evidenced by recognizable fault scarps such as Red Hill at the extreme southern extent of the fault near Foothill Boulevard. The fault is a known barrier to groundwater flow and groundwater elevation differences on the order of several hundred feet on opposite sides of the fault are typical (Eckis, 1934; DWR, 1970). Groundwater seeps across the Red Hill Fault as underflow to the Chino-1 and Chino-2 management zones, especially during periods of high groundwater elevations within the Cucamonga management zone.

· Extension of the Rialto-Colton Fault north of Barrier J. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along most of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto- Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). However, little well data exist to support its extension north of Barrier J (although hydraulic gradients are steep through this area, as shown in Figures 3-10 and 3-11). Groundwater flowing south out of Lytle Creek Canyon, in part, is deflected by Barrier J and likely flows across the extension of the Rialto-Colton Fault north of Barrier J and into the Chino-2 management zone.

· Flow system boundary with Chino-1 to the west. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within Chino- 1 and Chino-2 management zones. Figures 3-10 and 3-11 are two such maps that show areas of recharge located in the northern portions of Chino-1 and Chino-2 are distinct and spatially separated, in part, by the Cucamonga management zone. Water recharged in the northern portion of Chino-1 generally flows south (and, locally, to the west as a result of groundwater production patterns) staying southwest of the Cucamonga management zone. Water recharged in the northern portion of Chino-2 flows to the southwest, staying southeast of the Cucamonga management zone. Where these two flow systems meet, south of the Cucamonga management zone, groundwater flow directions are approximately parallel to each other. As groundwater flow continues south, the groundwater elevation contours suggest little, if any, cross-flow between flow systems. Nearing the southwestern (lowest) portion of the basin, these two flows systems become less distinct as all groundwater flow within Chino Basin converges and rises beneath Prado Basin. By analyzing groundwater elevation contours over a time, the management zone boundary that separates these consistent flow systems was drawn approximately parallel to groundwater flow direction from the point where the flow systems meet to discharge areas within Prado Basin.

· Flow system boundary with Chino-3 to the east. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within Chino- 2 and Chino-3 management zones. Figures 3-10 and 3-11 are two such maps that show the barrier effect of Barrier J (offset water levels) with groundwater elevations higher on the north

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side of Barrier J as it extends southwest of the Rialto-Colton Fault. Groundwater recharged north of Barrier J within Chino-2 flows to the southwest, staying north of Barrier J. Water recharged south of Barrier J within Chino-3 flows west and southwest, staying south of Barrier J. The barrier effect of Barrier J apparently diminishes to the southwest, but the flow systems in Chino-2 and Chino-3 continue to flow parallel to its southwestward extension. As groundwater flow continues southwest, the groundwater elevation contours suggest little, if any, cross-flow between flow systems. Nearing the southwestern (lowest) portion of the basin, these two flows systems become less distinct as all groundwater flow within Chino Basin converges and rises beneath Prado Basin. By analyzing groundwater elevation contours over a time, the management zone boundary that separates these consistent flow systems was drawn approximately parallel to groundwater flow direction from the location where Barrier J ceases to offset groundwater levels to discharge areas within Prado Basin.

· Prado Flood Control Basin to the south. Similar to the other management zones within the Chino Basin, Chino-2 pinches out to the south as groundwater is consumed by production and/or rises to become surface water in Prado Basin.

Management Zone: Chino-3

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills (Jurupa Mountains).

· Artificial recharge at spreading grounds.

· Underflow from the Rialto management zone as seepage across the Rialto-Colton Fault north of Slover Mountain. This underflow creates a groundwater mound (divide) in the vicinity of Bloomington and, hence, has been named the Bloomington Divide.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· North of the Jurupa Mountains, groundwater flow is westward from the Bloomington Divide and, thence, southwestward around the western tip of the Jurupa Mountains towards Prado Basin. Localized groundwater production has modified the general westward and southwestward flow directions in parts of the management zone (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Rising water within Prado Basin.

· Evapotranspiration within Prado Basin where groundwater is near or at the ground surface. Boundaries

· Flow system boundary with Chino-2 to the west. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within Chino- 2 and Chino-3 management zones. Figures 3-10 and 3-11 are two such maps that show the barrier effect of Barrier J (offset water levels) with groundwater elevations higher on the north side of Barrier J as it extends southwest of the Rialto-Colton Fault. Groundwater recharged north of Barrier J within Chino-2 flows to the southwest, staying north of Barrier J. Water

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recharged south of Barrier J within Chino-3 flows west and southwest, staying south of Barrier J. The barrier effect of Barrier J apparently diminishes to the southwest, but the flow systems in Chino-2 and Chino-3 continue to flow parallel to its southwestward extension. As groundwater flow continues southwest, the groundwater elevation contours suggest little, if any, cross-flow between flow systems. Nearing the southwestern (lowest) portion of the basin, these two flows systems become less distinct as all groundwater flow within Chino Basin converges and rises beneath Prado Basin. By analyzing groundwater elevation contours over a time, the management zone boundary that separates these consistent flow systems was drawn approximately parallel to groundwater flow direction from the location where Barrier J ceases to offset groundwater levels to discharge areas within Prado Basin.

· Rialto-Colton Fault to the northeast. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along much of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto-Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). The disparity in groundwater elevations across the fault decreases to the south. To the north of Slover Mountain, a gap in the Rialto-Colton Fault exists. Groundwater within the Rialto-Colton Basin passes through this gap to form a broad groundwater mound (divide) in the vicinity of Bloomington and, hence, is called the Bloomington Divide (Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970).

· Bloomington Divide to the east. A flattened mound of groundwater exists beneath the Bloomington area as a likely result of groundwater flow from the Rialto-Colton Basin through a gap in the Rialto-Colton Fault north of Slover Mountain (Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). This mound of groundwater extends from the gap in the Rialto- Colton Fault to the southwest towards the northeast tip of the Jurupa Mountains. Groundwater to the northwest of this divide recharges the Chino-3 management zone and flows westward staying north of the Jurupa Mountains. Groundwater southeast of the divide recharges the Riverside-B management zone and flows southwest towards the Santa Ana River.

· Jurupa Mountains to the south. The Jurupa Mountains are primarily composed of impermeable bedrock and form a barrier to groundwater flow between the Chino-3 management zone and the Chino-4 and Riverside-C management zones.

· Flow system boundary with Chino-4 and Chino-5 to the south. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within Chino-3 from the flow systems within the Chino-4 and Chino-5 management zones (Figures 3-10 and 3-11). As groundwater within Chino-3 flows around the western tip of the Jurupa Mountains, it converges with a relatively small flow system that exits the Glen Avon area south of the Jurupa Mountains (Chino-4). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two systems. The management zone boundary that separates Chino-3 and Chino-4 was drawn approximately parallel to groundwater flow direction from the northwest tip of the Jurupa Mountains toward Prado Basin. The “pinching out” of Chino-4 reflects the production of all groundwater that exits the Glen Avon area before it reaches Prado Basin. Based on a decision by the TIN/TDS Task Force, this boundary was altered slightly so that a JCSD well field is now included in Chino-3 (Figure 3-12). As groundwater within Chino-3 continues to flow southwest toward Prado Basin, in converges with the groundwater flow system associated with the Santa Ana River (Chino-5). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two flow systems. The management zone boundary that separates Chino-3 from Chino-5 was drawn approximately parallel to groundwater flow direction from the point where Chino-4 pinches out to the Prado Basin.

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· Prado Flood Control Basin to the south. Similar to the other management zones within the Chino Basin, Chino-3 pinches out to the south as groundwater is consumed by production and/or rises to become surface water in Prado Basin.

Management Zone: Chino-4

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills (Jurupa Mountains and Pedley Hills).

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flow is away from areas of recharge along bordering mountain fronts and, thence, westward toward the central Chino Basin. Localized groundwater production has modified the general westward flow direction in parts of the management zone (see Figures 3- 10 and 3-11). Discharge

· Groundwater production. Boundaries

· Flow system boundaries with Chino-3 and Chino-5 to the northwest and southwest, respectively. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within the Chino-3, Chino-4, and Chino-5 management zones (Figures 3-10 and 3-11). As the relatively small flow system of Chino-4 exits the Glen Avon area south of the Jurupa Mountains, it converges with groundwater flowing around the northwestern tip of the Jurupa Mountains (Chino-3). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two systems. The management zone boundary that separates Chino-3 and Chino-4 was drawn approximately parallel to groundwater flow direction from the northwest tip of the Jurupa Mountains toward Prado Basin. The “pinching out” of Chino-4 reflects the production of all groundwater that exits the Glen Avon area before it reaches Prado Basin. As the relatively small flow system of Chino-4 exits the Glen Avon area north of the Pedley Hills, in converges with the groundwater flow system associated with the Santa Ana River (Chino-5). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two flow systems. The management zone boundary that separates Chino-4 from Chino-5 was drawn approximately parallel to groundwater flow direction from the southern Pedley Hills to the point where Chino-4 pinches out.

· Jurupa Mountains and Pedley Hills to the north and south, respectively. The Jurupa Mountains and Pedley Hills are primarily composed of impermeable bedrock and form a barrier to groundwater flow that separates the Chino-4 management zone from the Chino-3, Riverside-C, and Chino-5 management zones.

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Management Zone: Chino-5

Recharge

· Infiltration of storm water flow and municipal wastewater discharges within the channel of the Santa Ana River.

· Infiltration of flow within other unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock hills.

· Intermittent underflow from the Temescal management zone.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flow generally follows the course of the Santa Ana River westward from the Riverside Narrows and, thence, southwestward around the La Sierra Hills towards Prado Basin (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Rising water within Prado Basin (and potentially other locations along the Santa Ana River depending on climate and season).

· Evapotranspiration within Prado Basin (and potentially other locations along the Santa Ana River depending on climate and season) where groundwater is near or at the ground surface. Boundaries

· Flow system boundaries with Chino-3 and Chino-4 to the northwest. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between the flow systems within the Chino-3, Chino-4, and Chino-5 management zones (Figures 3-10 and 3-11). As the relatively small flow system of Chino-4 exits the Glen Avon area north of the Pedley Hills, it converges with the groundwater flow system associated with the Santa Ana River (Chino-5). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two flow systems. The management zone boundary that separates Chino-4 from Chino-5 was drawn approximately parallel to groundwater flow direction from the southern Pedley Hills to the point where Chino-4 pinches out as a result of groundwater production. As groundwater within Chino-5 continues to flow westward, it converges with the groundwater flowing southwest within Chino-3, and begins to flow southwest towards Prado Basin. Analysis of groundwater elevation contour maps over time suggest little, if any, cross- flow between these two flow systems. The management zone boundary that separates Chino-3 from Chino-5 was drawn approximately parallel to groundwater flow direction from the point where Chino-4 pinches out to the Prado Basin.

· Pedley Hills and La Sierra Hills to the north and south, respectively. The Pedley and La Sierra Hills are primarily composed of impermeable bedrock and form a barrier to groundwater flow between the Chino-5 management zone and the Chino-4, Riverside-C, and Arlington management zones.

· Shallow bedrock at the Riverside Narrows to the east. Between the communities of Pedley and Rubidoux, the impermeable bedrock that outcrops on either side of the Santa Ana River narrows considerably. In addition, the alluvial thickness underlying the Santa Ana River thins

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to approximately 100 feet or less (i.e. shallow bedrock). This area of narrow and shallow bedrock along the Santa Ana River is commonly referred to as the Riverside Narrows. Groundwater upgradient of the Riverside Narrows is forced to the surface to become rising water within the Santa Ana River (Eckis, 1934). Downstream of the Riverside Narrows, the bedrock configuration widen and deepens, and surface water within the Santa Ana River can infiltrate to become groundwater.

· Flow system boundary with Temescal management zone to the south. Comparison of groundwater elevation contour maps over time suggest a consistent distinction between flow systems within the Chino-5 and Temescal management zones. As groundwater within Chino- 5 flows southwest into the Prado Basin area, it converges with groundwater flowing northwest out of the Temescal Valley (Temescal management zone). These groundwaters commingle and flow southwest toward Prado Dam and rise to become surface water in Prado Basin. This area of convergence of Chino-5 and Temescal groundwaters is indistinct and probably varies with changes in climate and production patterns. As a result, the management zone boundary that separates Chino-5 from Temescal was drawn along the legal boundary of the Chino Basin (Chino Basin Municipal Water District v. City of Chino, et al., San Bernardino Superior Court, No. 164327).

· Prado Flood Control Basin to the southwest. Similar to the other management zones within the Chino Basin, Chino-5 pinches out to the southwest as groundwater is consumed by production and/or rises to become surface water in Prado Basin.

Management Zone: Rialto

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the San Gabriel Mountains.

· Artificial recharge at spreading grounds.

· Underflow from the Lytle management zone as seepage across Barrier E.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southeastward from areas of recharge in the north toward areas of discharge in the south. However, Barrier J is an effective barrier to groundwater flow in the north, especially during times of relatively low groundwater elevations (Dutcher and Garrett, 1963). Groundwater north of Barrier J is, in part, deflected by Barrier J and flows to the southwest toward Chino-2 management zone. During times of relatively high groundwater elevations, groundwater north of Barrier J, in part, overtops Barrier J and flows southeastward toward the Colton management zone (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow across the Rialto-Colton Fault north of Barrier J into the Chino-2 management zone.

· Underflow across the Rialto-Colton Fault north of Slover Mountain into the Chino-3 and Riverside-B management zones.

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Boundaries

· Cucamonga Fault Zone/San Gabriel Mountains to the north. The Cucamonga Fault is a major, active fault zone, and is in part responsible for uplift of the San Gabriel Mountains, which are composed of impermeable metamorphic and igneous bedrock. The management zone boundary was mapped along the mountain front at the contact between the impermeable bedrock and the water-bearing alluvium.

· San Jacinto Fault and Barrier E to the northeast. The San Jacinto Fault and Barrier E separate the Rialto from the Bunker Hill-A and Lytle management zones, respectively. South of Barrier J, the San Jacinto Fault and Barrier E are competent barriers to groundwater flow as indicated by higher groundwater elevations within the Lytle management zone (Dutcher and Garrett, 1963). North of Barrier J, there is little evidence of the extension of Barrier E to the San Gabriel Mountains. Groundwater likely flows across the extension of Barrier E north of Barrier J into the Rialto management zone. Some underflow also may occur across Barrier E south of Barrier J into the Rialto management zone (Woolfenden and Kadhim, 1997).

· Rialto-Colton Fault to the southwest. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along much of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto-Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). The disparity in groundwater elevations across the fault decreases to the south. To the north of Slover Mountain, a gap in the Rialto-Colton Fault exists. Groundwater within the Rialto management zone passes through this gap to form a broad groundwater mound (divide) in the vicinity of Bloomington and, hence, is called the Bloomington Divide (Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). Little well data exist to support the extension of the Rialto-Colton Fault north of Barrier J (although hydraulic gradients are steep through this area, as shown in Figures 3-10 and 3-11). Groundwater flowing south out of Lytle Creek Canyon, in part, is deflected by Barrier J and likely flows across the extension of the Rialto-Colton Fault north of Barrier J and into the Chino-2 management zone.

· Flow system boundary with the Colton management zone to the south. In the Colton area, groundwater flowing south in the Rialto management zone meets groundwater flowing west in the Colton management zone and, thence, flows southwest to discharge across the Rialto- Colton Fault into the Riverside Basins. (Eckis, 1934; Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two flow systems. The management zone boundary that separates the Rialto and Colton management zones was drawn approximately parallel to groundwater flow direction where these two flow systems meet from the San Jacinto Fault to the Rialto-Colton Fault.

Management Zone: Colton

Recharge

· Infiltration of flow within the channels of the Santa Ana River and Warm Creek.

· Infiltration of storm water within unlined stream channels exiting Reche Canyon and the San Timoteo Badlands.

· Underflow from the saturated sediments and fractures within the surrounding bedrock mountains and hills.

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· Underflow as seepage across the San Jacinto Fault from the Bunker Hill-A and Bunker Hill-B management zones.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows westward from the primary area of recharge in the east (underflow across the San Jacinto Fault) toward areas of discharge in the west (underflow across the Rialto-Colton Fault). Groundwater within the alluvium and semi-consolidated rocks in Reche Canyon flows northwest to commingle with groundwaters in the main aquifer underlying the Santa Ana River (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow across the Rialto-Colton Fault (primarily within the shallow, recent alluvium underlying the Santa Ana River floodplain) into the Riverside-A management zone. Boundaries

· Flow system boundary with the Rialto management zone to the north. In the Colton area, groundwater flowing southeast in the Rialto management zone meets groundwater flowing northwest in the Colton management zone and, thence, flows southwest to discharge across the Rialto-Colton Fault into the Riverside Basins. (Eckis, 1934; Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two flow systems. The management zone boundary that separates the Rialto and Colton management zones was drawn approximately parallel to groundwater flow direction where these two flow systems meet from the San Jacinto Fault to the Rialto-Colton Fault.

· San Jacinto Fault to the northeast. The San Jacinto Fault separates the Colton from the Bunker Hill-A and Bunker Hill-B management zones. The San Jacinto Fault is competent barrier to groundwater flow in this area within the deep, older alluvium, but not within the shallow, recent alluvium underlying the channels of the Santa Ana River and Warm Creek (Dutcher and Garrett, 1963). Groundwater flows across the San Jacinto Fault within the shallow alluvium from the upgradient Bunker Hill Basin into the Colton management zone.

· Rialto-Colton Fault to the southwest. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along much of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto-Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). However, the disparity in groundwater elevations across the fault decreases to the south, indicating the barrier effect of the fault also decreases to the south. Many studies have postulated that groundwater flows freely across the Rialto-Colton Fault within aquifers underlying the Santa Ana River (Eckis, 1934; Gosling, 1966; DWR, 1970). However, in this same area, recent geophysical investigations (Ryland Associates, 1995) and hydrologic studies (Gosling, 1966) indicate the existence and the barrier effect of the Rialto-Colton Fault within the deep, older alluvium.

· Bedrock Mountains bordering Reche Canyon to the south. The mountains bordering Reche Canyon to the west and south are composed of impermeable metamorphic and igneous bedrock. The San Jacinto Fault borders Reche Canyon to the northeast. The fault cuts through the semi-consolidated sediments of the San Timoteo Badlands to form an impermeable barrier to groundwater flow.

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Management Zone: Riverside-A

Recharge

· Infiltration of flow within the channel of the Santa Ana River.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock hills.

· Underflow as seepage across the Rialto-Colton Fault from the Colton management zone.

· Underflow from the surrounding management zones (Riverside B through Riverside F).

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southwestward following the course of the Santa Ana River. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Rising water within the channel of the Santa Ana River upstream of the Riverside Narrows.

· Evapotranspiration along the Santa Ana River where groundwater is near or at the ground surface. Boundaries

· Rialto-Colton Fault to the northeast. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along much of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto-Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). However, the disparity in groundwater elevations across the fault decreases to the south, indicating the barrier effect of the fault also decreases to the south. Many studies have postulated that groundwater flows freely across the Rialto-Colton Fault within aquifers underlying the Santa Ana River (Eckis, 1934; Gosling, 1966; DWR, 1970). However, in this same area, recent geophysical investigations (Ryland Associates, 1995) and hydrologic studies (Gosling, 1966) indicate the existence and the barrier effect of the Rialto-Colton Fault within the deep, older alluvium.

· Flow system boundaries with the surrounding Riverside management zones. The flow systems of Riverside-B through Riverside-F surround and are tributary to Riverside-A. Conversely, groundwater within Riverside-A is not tributary to the surrounding Riverside management zones. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration. {Note: One possible exception to the above is the northern boundary between Riverside-A and Riverside-F in the Grand Terrace area. Eckis (1934) speculated that groundwater beneath the Santa Ana River (Riverside-A) can flow into the Grand Terrace area (Riverside-F) based on groundwater elevation contour maps. However, Basin Planning Model simulations indicate

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that this flow is minor compared to flow around the north side of La Loma Hills (i.e. groundwater flow within Riverside-A). (Wildermuth, pers. comm., 1999).} Lastly, Riverside-A includes the areas recharged by groundwater underflow from the Colton management zone, since Colton also is recharged by surface water in the Santa Ana River.

· Numerous internal bedrock hills. Numerous hills protruding from the valley floor of the Riverside Basins are composed of impermeable metamorphic and igneous bedrock. These hills typically act as impermeable barriers between distinct flow systems and, hence, are used as management zone boundaries.

· Shallow bedrock at the Riverside Narrows to the southwest. Between the communities of Pedley and Rubidoux, the impermeable bedrock that outcrops on either side of the Santa Ana River narrows considerably. In addition, the alluvial thickness underlying the Santa Ana River thins to approximately 100 feet (i.e. shallow bedrock). This area of narrow and shallow bedrock along the Santa Ana River is commonly referred to as the Riverside Narrows. Groundwater upgradient of the Riverside Narrows (flowing southwest within Riverside-A) is forced to the surface to become rising water within the Santa Ana River (Eckis, 1934).

Management Zone: Riverside-B

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains.

· Underflow as seepage across the Rialto-Colton Fault from the Rialto management zone.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southwestward from areas of recharge along the Rialto-Colton Fault toward the Jurupa Mountains and, thence, south toward the Santa Ana River and Riverside-A. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow to Riverside-A management zone. Boundaries

· Rialto-Colton Fault to the northeast. The Rialto-Colton Fault separates the Rialto-Colton Basin from the Chino and Riverside basins. The fault is a known barrier to groundwater flow along much of its length – especially in its northern reaches (south of Barrier J) where groundwater elevations can be hundreds of feet higher within the Rialto-Colton Basin (Dutcher and Garrett, 1963; DWR, 1970; Woolfenden and Kadhim, 1997). However, the disparity in groundwater elevations across the fault decreases to the south. To the north of Slover Mountain, a gap in the Rialto-Colton Fault exists. Groundwater within the Rialto management zone passes through this gap to form a broad groundwater mound (divide) in the vicinity of Bloomington and, hence, is called the Bloomington Divide (Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). To the south of this gap, many studies have postulated that groundwater flows freely across the Rialto-Colton Fault (Eckis, 1934; Gosling, 1966; DWR, 1970). However, recent geophysical investigations (Ryland Associates, 1995) and

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hydrologic studies (Gosling, 1966) indicate the existence and the barrier effect of the Rialto- Colton Fault within the deep, older alluvium.

· Bloomington Divide to the northwest. A flattened mound of groundwater exists beneath the Bloomington area as a likely result of groundwater flow from the Rialto-Colton Basin through a gap in the Rialto-Colton Fault north of Slover Mountain (Dutcher and Moyle, 1963; Gosling, 1966; DWR, 1970). This mound of groundwater extends from the gap in the Rialto- Colton Fault to the southwest towards the northeast tip of the Jurupa Mountains. Groundwater to the northwest of this divide recharges the Chino-3 management zone and flows westward staying north of the Jurupa Mountains. Groundwater southeast of the divide recharges the Riverside-B management zone and flows southwest towards the Santa Ana River.

· Jurupa Mountains/groundwater divide to the west. The Jurupa Mountains are composed of impermeable metamorphic and igneous bedrock. Within these mountains, a narrow alluvial-filled canyon connects the Riverside-B and Riverside-C management zones. A groundwater divide within this canyon delineates the management zone boundary between Riverside-B and Riverside-C.

· Flow system boundary with Riverside-A management zone to the southeast. The flow system of Riverside-B is tributary to Riverside-A. Conversely, the flow system of Riverside- A is not tributary to Riverside-B. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone, and has no water quality impact upon Riverside-B. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration. Riverside-A also includes areas recharged by groundwater underflow from the Colton management zone, since Colton also is recharged by surface water in the Santa Ana River. Riverside-B includes areas recharged by groundwater underflow from the Rialto management zone. As a result, the management zone boundary between Riverside-A and Riverside-B intersects the Rialto-Colton Fault at the same location as the boundary between the Rialto and Colton management zones.

Management Zone: Riverside-C

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southward toward the Santa Ana River and Riverside-A. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow to Riverside-A management zone.

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Boundaries

· Pedley Hills and Jurupa Mountains/groundwater divide to the north. The surrounding Pedley Hills and Jurupa Mountains are composed of impermeable metamorphic and/or igneous bedrock. Within these mountains, a narrow alluvial-filled canyon connects the Riverside-B and Riverside-C management zones. A groundwater divide within this canyon delineates the management zone boundary between Riverside-B and Riverside-C.

· Flow system boundary with Riverside-A management zone to the south. The flow system of Riverside-C is tributary to Riverside-A. Conversely, the flow system of Riverside-A is not tributary to Riverside-C. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone, and has no water quality impact upon Riverside-C. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration.

Management Zone: Riverside-D

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows northward from areas of recharge along the bedrock hills in the south toward the Santa Ana River and Riverside-A. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow to Riverside-A management zone. Boundaries

· Groundwater divide to the west. A flattened mound of groundwater exists beneath the Arlington area, and acts as a groundwater divide between the Arlington and Riverside basins (Eckis, 1934). This mound of groundwater extends from the bedrock hills in the south to the eastern La Sierra Hills in the north, approximately coinciding with Adams Street. Groundwater to the southwest of this divide flows westward within the Arlington management zone. Groundwater northeast of the divide flows northward within the Riverside- D management zone towards the Santa Ana River.

· Bedrock hills to the southeast. The elevated bedrock hills that separate the Riverside Basins from the San Jacinto Basins are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Flow system boundary with Riverside-E to the east. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between flow systems within the Riverside-D and Riverside-E management zones (Figures 3-10 and 3-11). The irregular configuration of the bedrock hills to the southeast separates the recharges areas flanking these

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hills within Riverside-D from recharge areas within Riverside-E. As groundwater flows northwestward from these recharge areas, the flow systems merge, and continue to flow northwestward toward the Santa Ana River. Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two systems. The management zone boundary that separates Riverside-D and Riverside-E was drawn approximately parallel to groundwater flow direction from the bedrock hills in the southeast to the Riverside-A management zone.

· Flow system boundary with Riverside-A management zone to the north. The flow system of Riverside-D is tributary to Riverside-A. Conversely, the flow system of Riverside-A is not tributary to Riverside-D. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone, and has no water quality impact upon Riverside-D. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration.

Management Zone: Riverside-E

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows westward from areas of recharge along the bedrock hills in the southeast toward the Santa Ana River and Riverside-A. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow to Riverside-A management zone. Boundaries

· Bedrock hills to the southeast. The elevated bedrock hills that separate the Riverside Basins from the San Jacinto Basins are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Flow system boundaries with Riverside-D and Riverside-F to the south and north, respectively. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between flow systems within the Riverside-D, Riverside-E, and Riverside-F management zones (Figures 3-10 and 3-11). The irregular configuration of the bedrock hills to the southeast separates the recharges areas flanking these hills within Riverside-E from recharge areas within Riverside-D and Riverside-F. As groundwater flows northwestward from these recharge areas, the flow systems merge, and continue to flow northwestward toward the Santa Ana River. Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two systems. The management zone boundaries that separate Riverside-E from Riverside-D and Riverside-F were drawn

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approximately parallel to groundwater flow direction from the bedrock hills in the southeast to the Riverside-A management zone.

· Flow system boundary with Riverside-A management zone to the north. The flow system of Riverside-E is tributary to Riverside-A. Conversely, the flow system of Riverside-A is not tributary to Riverside-E. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone, and has no water quality impact upon Riverside-E. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration.

Management Zone: Riverside-F

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Potentially small amounts of underflow from Riverside-A management zone northeast of La Loma Hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southwestward from areas of recharge along the bedrock hills in the east toward the Santa Ana River and Riverside-A. (see Figures 3-10 and 3-11). Discharge

· Groundwater production.

· Underflow to Riverside-A management zone. Boundaries Flow system boundary with Riverside-A management zone to the north. This management zone boundary is drawn along an elevated cut-bank of the Santa Ana River, which also is a geologic contact between the recent deposits of the Santa Ana River and the older alluvial deposits of the Grand Terrace/Riverside area (Eckis, 1934). Eckis (1934) speculated that groundwater beneath the Santa Ana River (Riverside-A) can flow into the Grand Terrace area (Riverside-F) based on groundwater elevation contour maps. However, Basin Planning Model simulations indicate that this flow is minor compared to flow around the north side of La Loma Hills (i.e. groundwater flow within Riverside-A). (Wildermuth, pers. comm., 1999).

· Bedrock hills to the southeast. The elevated bedrock hills that separate the Riverside Basins from the San Jacinto Basins and Reche Canyon are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Flow system boundary with Riverside-E to the south. Comparison of groundwater level contour maps over time demonstrates a consistent distinction between flow systems within the Riverside-F and Riverside-E management zones (Figures 3-10 and 3-11). The irregular configuration of the bedrock hills to the southeast separates the recharges areas flanking these

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hills within Riverside-F from recharge areas within Riverside-E. As groundwater flows westward from these recharge areas, the flow systems merge, and continue to flow westward toward the Santa Ana River. Analysis of groundwater elevation contour maps over time suggest little, if any, cross-flow between these two systems. The management zone boundary that separates Riverside-F and Riverside-E was drawn approximately parallel to groundwater flow direction from the Box Springs Mountains in the east to the Riverside-A management zone.

· Flow system boundary with Riverside-A management zone to the west. The flow system of Riverside-F is tributary to Riverside-A along this boundary. Conversely, the flow system of Riverside-A is not tributary to Riverside-F along this boundary. The philosophy behind this alignment of management zones is that water recharged within the Santa Ana River channel is confined to the Riverside-A management zone. Analysis of groundwater elevation contour maps over time determined the extent of lateral migration of groundwater recharged within the Santa Ana River channel. The management zone boundaries were then drawn along these lines of extent of lateral migration.

3.3.4 Elsinore – Temescal Valleys

The Elsinore and Temescal Valleys are a northwest-trending faulted graben (commonly known as the Elsinore Trough) bounded by the elevated Perris Block on the northeast and the on the southwest. The Elsinore and Chino fault zones are the primary structural features in the valley and are responsible for uplift of the Santa Ana Mountains and depression of the Elsinore Trough (Eckis, 1934). Temescal Wash is the main tributary draining these valleys. Sediments eroded from igneous and metamorphic rocks within the surrounding mountains have filled these valleys to provide reservoirs for groundwater.

The groundwater basin underlying Arlington (Arlington Basin) is northeast of the Temescal Valley between the La Sierra Hills to the north and low bedrock hills of the Perris Block to the south. While the Arlington Basin is similar to the Riverside Basins in its physical configuration and structural origin, it is included in this description of the groundwater basins within the Elsinore and Temescal valleys because its groundwater is tributary to the Temescal Valley.

Figure 3-13 is an equal elevation contour map of the effective base of the freshwater aquifers in this region. Note the numerous bounding faults and the steep slope of the base of the freshwater beneath (Elsinore Basin). The Elsinore Basin is shallow on its perimeter, but is extremely deep at its center (greater than 2,000 feet below ground surface) due to intense faulting and contemporaneous sedimentation (Geoscience, 1994). The Coldwater Basin, located northwest of the Elsinore Basin between the North Glen Ivy and South Glen Ivy faults, is similar in structural origin and reaches a maximum depth of about 700 feet. The Temescal and Arlington basins to the north are comparatively broad and shallow, but exhibit a channel-like bedrock feature parallel to the long axis of each basin (Eckis, 1934; DWR, 1970).

The base of the aquifer underlying the central portion of the Temescal Valley is unmapped, and the literature review performed in this study did not locate such a map. The significant aquifers within this region are restricted to a narrow band of saturated alluvium along Temescal Wash. Analysis of driller’s logs of wells located along this reach of Temescal Wash indicates consolidated, non-water-bearing bedrock at a depth of about 100 feet below ground surface.

Predominant recharge to the groundwater reservoirs in the area is from percolation of precipitation and infiltration of stream flow within tributaries exiting the surrounding mountains and hills. In addition,

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municipal wastewater is discharged at a number of points along unlined portions of Temescal Wash, which also percolates to become groundwater.

In general, groundwater flow mimics surface drainage patterns. Figures 3-14 and 3-15 are groundwater elevation contour maps for Fall 1973 and Fall 1997 that show this general groundwater flow pattern. The Elsinore Basin is practically surrounded by impermeable bedrock hills, and surface water drains internally to Lake Elsinore. Similarly, groundwater flows internally – from the flanks of the surrounding hills (areas of recharge) towards the main groundwater reservoirs underlying Lake Elsinore. Groundwater does not exit the Elsinore Basin except via groundwater production and evapotranspiration where and when groundwater is near the ground surface. In the Temescal Valley and the Arlington Basin, groundwater flows from the flanks of the surrounding hills (areas of recharge) toward surface drainage tributaries (e.g. Temescal Wash and the Arlington Drain) and, thence, toward Prado Basin (area of discharge).

Comparing the groundwater elevation contour maps of Figures 3-14 and 3-15, note that groundwater flow paths (perpendicular to the contours) are generally similar. Groundwater elevation contour maps from other periods (either from the literature or constructed for this study) also show similar flow paths, indicating consistent flow systems within this area.

We have delineated seven management zones within the Elsinore – Temescal Valleys based on major impermeable boundaries, bedrock constrictions, groundwater divides, and surface water divides (Figure 3-16):

· Elsinore

· Warm Springs Valley

· Lee Lake

· Bedford

· Coldwater

· Temescal

· Arlington

Management Zone: Elsinore

Recharge

· Infiltration of flow within the channel of the San Jacinto River, which receives intermittent discharge from Railroad Canyon Reservoir (Black & Veatch, 1994).

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Artificial recharge of native waters at spreading grounds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flows internally from the flanks of the surrounding bedrock hills (areas of recharge) toward the main groundwater reservoir underlying Lake Elsinore. (see Figures 3-14

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and 3-15). Numerous faults along the flanks of the surrounding bedrock hills are barriers to groundwater flow. However, groundwater can leak through these faults to recharge the main aquifers underlying Lake Elsinore (Geoscience, 1994).

· Under pre-pumping conditions, rising groundwater on the upgradient side of the surrounding faults occurred in some areas, and groundwater within the main reservoir flowed toward Lake Elsinore. Pumping has significantly lowered groundwater elevations throughout the basin – in some areas by several hundred feet – such that rising groundwater no longer occurs and groundwater gradients away from Lake Elsinore now exist (note the “pumping hole” in Figure 3-15 located in the vicinity of Corydon Road). Discharge

· Groundwater production.

· Evapotranspiration where and when groundwater is near the ground surface. Boundaries

· Bedrock hills surrounding most of the management zone. The elevated bedrock hills that surround Lake Elsinore are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Surface water divide to the southeast. A surface water divide between the Lake Elsinore watershed and the Murrieta Creek watershed is mapped as the management zone boundary to the southeast. Groundwater elevation contours in 1997 (see Figure 3-15) show a groundwater gradient across this boundary from the Murrieta Creek area toward Lake Elsinore. However, sediments that compose the groundwater reservoirs in this area are known to be of low permeability (MacRostie and Dolcini, 1959) and groundwater flow across this boundary is of low volume (D. Williams, pers. comm., 1999).

· Shallow, narrow bedrock gap along Temescal Wash outlet. A narrow gap in the bedrock exists where Lake Elsinore discharges to Temescal Wash during times of high lake levels. The bedrock is shallow and the alluvium is thin in this area, and groundwater does not escape through this gap from the main groundwater reservoirs of the management zone. The management zone boundary is drawn at the narrowest bedrock constriction within this gap.

Management Zone: Warm Springs Valley

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Infiltration of municipal wastewater discharged to Temescal Wash.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater elevation data could not be obtained for wells within this management zone and, hence, the construction of groundwater elevation contour maps was impossible. The literature collected for this study did not include hydrogeologic descriptions of this area.

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· Currently, the alluvium along Temescal Wash upstream of Walker Canyon is completely saturated due, in part, to municipal wastewater discharge to Temescal Wash. It is unclear how this discharge has impacted groundwater flow in the area. Discharge

· Groundwater production, if it exists.

· Temescal Wash through Walker Canyon is the only surface water discharge from Warm Springs Valley. Currently, the alluvium along Temescal Wash upstream of Walker Canyon is completely saturated due, in part, to municipal wastewater discharge to Temescal Wash. It is unclear how this discharge has impacted groundwater discharge from this area.

· Evapotranspiration where groundwater is near the ground surface. Boundaries

· Bedrock hills surrounding most of the management zone. The elevated bedrock hills that surround Warm Springs Valley are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Shallow, narrow bedrock gap along Temescal Wash at Walker Canyon. A narrow gap in the bedrock exists where Temescal Wash discharges to Walker Canyon (and to the Lee Lake management zone). The bedrock is shallow and the alluvium is thin at this gap. However, the alluvium is completely saturated upstream of Walker Canyon, and groundwater may escape through the gap into Walker Canyon. The management zone boundary is drawn at the upstream mouth of Walker Canyon.

Management Zone: Lee Lake

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone, primarily Temescal Wash.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Percolation of water within Lee Lake reservoir.

· Artificial recharge of native waters at spreading grounds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flows from the flanks of the surrounding bedrock hills (areas of recharge) toward Temescal Wash and, thence, northwestward following the downstream course of Temescal Wash (see Figures 3-14 and 3-15). Discharge

· Groundwater production.

· Evapotranspiration where and when groundwater is near the ground surface.

· Underflow through a narrow bedrock canyon along Temescal Wash.

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Boundaries

· Shallow, narrow bedrock gap along Temescal Wash at Walker Canyon. A narrow gap in the bedrock exists where Temescal Wash discharges to Walker Canyon (from the Warm Springs Valley management zone). The bedrock is shallow and the alluvium is thin at this gap. However, the alluvium is completely saturated upstream of Walker Canyon, and groundwater may escape through the gap into Walker Canyon. The management zone boundary is drawn at the upstream mouth of Walker Canyon.

· Bedrock hills surrounding most of the management zone. The elevated bedrock hills that surround Temescal Valley (and Lee Lake management zone) are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Narrow bedrock canyon along Temescal Wash downstream of Lee Lake reservoir. Temescal Wash enters a narrow bedrock canyon directly downstream of Lee Lake reservoir. The bedrock is shallow and the alluvium is thin in this area, but groundwater can exit Lee Lake management zone (and enter Bedford management zone) as underflow through the sediments underlying Temescal Wash. The management zone boundary is drawn within this canyon.

Management Zone: Bedford

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone, primarily Temescal Wash.

· Underflow from the saturated alluvium and fractures within the surrounding bedrock mountains and hills.

· Underflow through a narrow bedrock canyon along Temescal Wash from the Lee Lake management zone.

· Underflow from the Coldwater Basin as seepage across the North Glen Ivy Fault.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flows from the flanks of the surrounding bedrock hills (areas of recharge) toward Temescal Wash and, thence, northwestward following the downstream course of Temescal Wash (see Figures 3-14 and 3-15). Discharge

· Groundwater production.

· Evapotranspiration where and when groundwater is near the ground surface.

· Underflow through a narrow bedrock canyon along Temescal Wash to the Temescal management zone. Boundaries

· Narrow bedrock canyon along Temescal Wash downstream of Lee Lake reservoir. Temescal Wash enters a narrow bedrock canyon directly downstream of Lee Lake reservoir. The bedrock is shallow and the alluvium is thin in this area, but groundwater can exit Lee

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Lake management zone (and enter Bedford management zone) as underflow through the sediments underlying Temescal Wash. The management zone boundary is drawn within this canyon.

· Bedrock hills surrounding most of the management zone. The elevated bedrock hills that surround Temescal Valley (and Bedford management zone) are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· North Glen Ivy Fault to the west. The North Glen Ivy Fault separates the relatively deep Coldwater Basin from the thin aquifers associated with Temescal Wash (within the Bedford management zone). This fault is an effective barrier to groundwater flow, and underflow across this fault to the Bedford management zone occurs only after extensive recharge has filled the Coldwater Basin to capacity (John S. Murk Engineers, 1987).

· Narrow bedrock canyon along Temescal Wash downstream of Cajalco Road. Temescal Wash enters a narrow bedrock canyon directly downstream of Cajalco Road. The bedrock is shallow and the alluvium is thin in this area, but groundwater can exit Bedford management zone (and enter Temescal management zone) as underflow through the sediments underlying Temescal Wash. The management zone boundary is drawn within this canyon.

Management Zone: Coldwater

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the Santa Ana Mountains.

· Artificial recharge of storm flow at spreading grounds.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flows from the flanks of the Santa Ana Mountains (areas of recharge) toward the North Glen Ivy Fault and areas of extensive groundwater production (see Figures 3-14 and 3-15). Discharge

· Groundwater production.

· Evapotranspiration where and when groundwater is near the ground surface.

· Underflow to the Bedford management zone as seepage across the North Glen Ivy Fault. Boundaries

· Santa Ana Mountains to the west. The Santa Ana Mountains bound the Coldwater Basin to the west, and are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· North Glen Ivy Fault to the east. The North Glen Ivy Fault separates the relatively deep Coldwater Basin from the thin aquifers associated with Temescal Wash (within the Bedford management zone). This fault is an effective barrier to groundwater flow, and underflow

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across this fault to the Bedford management zone occurs only after extensive recharge has filled the Coldwater Basin to capacity (John S. Murk Engineers, 1987).

Management Zone: Temescal

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills.

· Percolation of water within a quarry pit south of Magnolia Avenue (Temescal Wash water).

· Artificial recharge of municipal wastewater at percolation ponds.

· Underflow from the Arlington and Bedford management zones.

· Intermittent underflow from the Chino management zones.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater flows from the flanks of the Santa Ana Mountains and other surrounding hills (areas of recharge) toward the center of the basin and, thence, northward toward the primary area of discharge at Prado Basin (see Figures 3-14 and 3-15). Discharge

· Groundwater production.

· Intermittent underflow to the Chino management zones.

· Rising water within or near Prado Basin and Temescal Wash.

· Evapotranspiration within or near Prado Basin and Temescal Wash where and when groundwater is at or near the ground surface. Boundaries

· Narrow bedrock canyon along Temescal Wash downstream of Cajalco Road. Temescal Wash enters a narrow bedrock canyon directly downstream of Cajalco Road. The bedrock is shallow and the alluvium is thin in this area, but groundwater can exit Bedford management zone (and enter Temescal management zone) as underflow through the sediments underlying Temescal Wash. The management zone boundary between Bedford and Temescal is drawn within this canyon.

· Santa Ana Mountains to the west and other surrounding hills. The Santa Ana Mountains and other surrounding hills are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Bedrock constriction to the east. Within the Arlington management zone to the east, the gap between the bedrock hills that boarder Arlington becomes narrow to the southwest (Figure 3- 13). Groundwater flows from Arlington through this narrow constriction of the water-bearing alluvium into the Temescal management zone (Eckis, 1934; DWR, 1970). The management zone boundary between Arlington and Temescal is drawn within the bedrock gap.

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· Flow system boundary with the Chino management zones to the north. Comparison of groundwater elevation contour maps over time suggest a consistent distinction between flow systems within the Chino and Temescal management zones. As groundwater within the Chino management zones flows south and southwest into the Prado Basin area, it converges with groundwater flowing northwest out of the Temescal management zone. These groundwaters commingle and flow southwest toward Prado Dam and rise to become surface water in Prado Basin. This area of convergence of Chino and Temescal groundwaters is indistinct and probably varies with changes in climate and production patterns. As a result, the management zone boundaries that separate Chino management zones from Temescal were drawn along the legal boundary of the Chino Basin (Chino Basin Municipal Water District v. City of Chino, et al., San Bernardino Superior Court, No. 164327).

Management Zone: Arlington

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows northward from the flanks of the bedrock hills in the south (areas of recharge) toward the center of the basin and, thence southwestward to exit the basin as underflow through a bedrock gap into the Temescal management zone. Some groundwater in the eastern portion of the management zone flows northward toward and discharges to Hole Lake (see Figure 3-14). Discharge

· Groundwater production.

· Underflow to Temescal management zone.

· Discharge to Hole Lake. Boundaries

· Groundwater divide to the west. A flattened mound of groundwater exists beneath the Arlington area, and acts as a groundwater divide between the Arlington and Riverside basins (Eckis, 1934). This mound of groundwater extends from the bedrock hills in the south to the eastern La Sierra Hills in the north, approximately coinciding with Adams Street. Groundwater to the southwest of this divide flows northwestward within the Arlington management zone. Groundwater northeast of the divide flows northward within the Riverside- D management zone.

· Bedrock hills. The elevated bedrock hills that surround the Arlington management zone are composed of impermeable metamorphic and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Bedrock constriction to the west. The gap between the bedrock hills that boarder the Arlington management zone becomes narrow to the southwest (Figure 3-13). Groundwater flows from Arlington through this narrow constriction of the water-bearing alluvium into the

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Temescal management zone (Eckis, 1934; DWR, 1970). The management zone boundary between Arlington and Temescal is drawn within the bedrock gap.

3.3.5 Orange County Basins

The Orange County groundwater basins overlie a broad, alluvial coastal plain located between the Santa Ana Mountains/Chino Hills to the northeast and the Pacific Ocean to the southwest. Structural folding and faulting along the basin margins, together with downwarping and contemporaneous sedimentation within the central portion of the basin, created the alluvial groundwater reservoirs underlying this region.

Figure 3-17 is an equal elevation contour map of the effective base of the freshwater aquifers in this region. The formations underlying the freshwater aquifers consist of consolidated low-permeability sedimentary rocks (Herndon et al., 1997). Note that the groundwater reservoirs lie within a northwest- trending synclinal structure that extends from the Irvine area to the Santa Monica Mountains in the far northwest (off the map). Also note the dramatic deepening of the base of the aquifer to the northwest – from the relatively shallow Irvine area (where thickness of freshwater-bearing sediments averages about 500 feet) to the deep central portion of the basin (where thickness of freshwater-bearing sediments can be greater than 4,000 feet).

Other major geologic features that relate to the physical boundaries of the Orange County Basins are the Newport-Inglewood Fault Zone and the Coyote Hills. The Newport-Inglewood Fault Zone parallels the coast and has uplifted impermeable bedrock to shallow depths, creating a natural barrier to seawater intrusion. The Coyote Hills, a folded and faulted uplift in the north, is primarily composed of impermeable bedrock and separates groundwaters in the La Habra area from the main Orange County basin.

The Santa Ana River is the main tributary draining the region from the Santa Ana Canyon (Prado Dam) to the Pacific Ocean at Huntington Beach. Other tributaries include San Diego Creek, which drains the Irvine area south of the Santa Ana River; and Coyote Creek, Brea Creek, and Carbon Creek, which drain the La Habra and Yorba Linda areas north of the Santa Ana River.

Predominant recharge to the groundwater reservoirs in the region is from infiltration of flow within the Santa Ana River channel, infiltration of flow within other tributaries exiting the surrounding mountains and hills, percolation of native and imported waters at recharge facilities operated by Orange County Water District (OCWD), groundwater injection at the Talbert Gap and Alamitos Barriers to inhibit seawater intrusion, and percolation of precipitation and returns from use. In general, recharge occurs at forebay areas in the northeast where the Santa Ana River exits Santa Ana Canyon. In the Irvine area, the forebay areas flank the hills to the east. Groundwater flow is from the forebay areas into the so-called Pressure Area in the central and coastal portions of the basin.

Figures 3-18 and 3-19 are groundwater elevation contour maps for Fall 1973 and Fall 1997 that show this general groundwater flow pattern. Comparing these two contour maps, note that groundwater flow paths (perpendicular to the contours) are generally similar. Groundwater elevation contour maps from other periods (constructed and provided by OCWD) also show similar flow paths, indicating consistent flow systems within this area. Variations in climate and groundwater production patterns modify flow directions locally, but the prevailing flow systems have remained intact over time.

Groundwater underlying the forebay areas typically exists under water-table to semi-confined conditions. Within the Pressure Area, groundwater typically exists under pressurized conditions due to the occurrence

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of extensive clay and silt layers that act to confine groundwater within underlying, coarse-grained aquifers.

We have delineated four management zones within the Orange County Basins based on major impermeable boundaries, bedrock constrictions, surface water divides, hydrogeologic parameters, internal flow systems, and the Pacific Ocean (Figure 3-20):

· Orange County

· Irvine

· La Habra

· Santiago

Management Zone: Orange County

Recharge

· Infiltration of flow within the Santa Ana River channel north of Katella Avenue. These flows include runoff from urban, agricultural and undeveloped areas, discharges from upstream wastewater treatment facilities, and discharges of imported water.

· Infiltration of flow within other unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills.

· Percolation of Santa Ana River water and imported water at OCWD recharge facilities located along the river, off-river, and along Santiago Creek.

· Groundwater injection at the Talbert Gap and Alamitos Barrier to inhibit seawater intrusion.

· Underflow through a bedrock gap in the Coyote Hills from the La Habra management zone.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southwestward from the forebay areas into the pressure aquifers occupying the central and coastal portions of the basin. Variations in climate and groundwater production patterns can modify flow directions locally, but the prevailing flow system remains intact (see Figures 3-18 and 3-19). Note the presence of a number of “pumping holes” in the Pressure Area during 1997 (Figure 3-19). Discharge

· Groundwater production.

· Underflow to the Central Basin across the Orange County/Los Angeles County line. Boundaries

· Bedrock mountains and hills the northeast. The Santa Ana Mountains and Chino Hills surround the Santa Ana Canyon and border the forebay area of the Orange County management zone on the northeast. These mountains and hills are composed of impermeable sedimentary, metamorphic, and/or igneous bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

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· Coyote Hills and flow system boundaries with the La Habra management zone to the north. The Coyote Hills are primarily composed of impermeable bedrock and separate the La Habra and Orange County management zones. However, the alluvium is continuous between the management zones in two areas. Groundwater within La Habra flows southward through a bedrock gap between the West Coyote Hills and the East Coyote Hills into the Orange County management zone. The management zone boundary is drawn at the narrowest point in this bedrock gap. To the east of the Coyote Hills, a flow system boundary exists between the La Habra and Orange County management zones. The management zone boundary is drawn from the eastern tip of the Coyote Hills to the Chino Hills in the northeast. Comparison of groundwater elevation maps show that groundwater west of this boundary flows to the north of the Coyote Hills in the La Habra management zone, while groundwater east of this boundary flows to the south of the Coyote Hills in the Orange County management zone (William R. Mills & Associates, 1987).

· Bedrock constriction along Santiago Creek. Santiago Creek flows out of the foothills of Santa Ana Mountains within a narrow bedrock canyon. The saturated alluvium within this canyon is the Santiago management zone. Downstream of Irvine Lake (and Villa Park Dam), the canyon widens and Santiago Creek flows onto the main coastal plain. The boundary between the Santiago and Orange County management zones is drawn across the mouth of the narrow canyon. Groundwater within the alluvium in the Santiago management zone can flow across this boundary and recharge the aquifers within the Orange County management zone.

· Hydrogeologic boundary with the Irvine management zone to the southeast. The groundwater reservoirs underlying the Irvine and Orange County management zones, while hydraulically continuous, are distinct and different in their hydrogeologic nature. The management zone boundary is aligned along State Highway 55, and represents the transition between the hydrogeologic regimes of the two management zones. Much of the information to support this management zone boundary comes from Singer (1973). First, recharge areas within the Irvine and Orange County management zones are spatially distinct. Recharge areas within Orange County are along the Santa Ana River and Santiago Creek, while recharge areas within Irvine are along the foothills of the Santa Ana Mountains and San Joaquin Hills. Second, thickness of the water-bearing alluvium increases dramatically from Irvine to Orange County across this boundary. Third, permeability of the water-bearing alluvium increases significantly from Irvine to Orange County – the percentage of clay within sediments is much higher within the Irvine management zone. Lastly, the amount of groundwater flow crossing this boundary is relatively small. This is shown by the groundwater elevation contour maps (see Figure 3-19) and in groundwater models constructed by OCWD (G. Woodside, pers. comm., 1999).

· Orange County/Los Angeles County line to the northwest. This is a political boundary that is unrelated to groundwater hydrology. Groundwater flows across this boundary, generally from the Orange County management zone into the Central Basin.

· Pacific Ocean to the west. This boundary is drawn along the shoreline. The Newport- Inglewood Fault Zone parallels the coast and has uplifted the impermeable bedrock to shallow depths, creating a natural barrier to seawater intrusion. However, groundwater production within the Orange County management zone has lowered groundwater levels and created a hydraulic gradient from the Pacific Ocean toward the aquifers underlying Orange County.

Management Zone: Irvine

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

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· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows westward from the forebay areas into the pressure aquifers occupying western and southwestern portions of the management zone. Variations in climate and groundwater production patterns can modify flow directions locally, but the prevailing flow system remains intact (see Figures 3-18 and 3-19). Discharge

· Groundwater production.

· Limited underflow to the Orange County management zone. Boundaries

· Bedrock mountains and hills the northeast. The San Joaquin Hills and the foothills of the Santa Ana surround the Irvine management zone on the south and north. These mountains and hills are primarily composed of impermeable sedimentary bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Surface water divide to the east. A surface water divide between the San Diego Creek and Aliso Creek watersheds is the management zone boundary to the east. The alluvium is extremely thin in this area and contains little groundwater.

· Hydrogeologic boundary with the Orange County management zone to the west. The groundwater reservoirs underlying the Irvine and Orange County management zones, while hydraulically continuous, are distinct and different in their hydrogeologic nature. The management zone boundary is aligned along State Highway 55, and represents the transition between the hydrogeologic regimes of the two management zones. Much of the information to support this management zone boundary comes from Singer (1973). First, recharge areas within the Irvine and Orange County management zones are spatially distinct. Recharge areas within Orange County are along the Santa Ana River and Santiago Creek, while recharge areas within Irvine are along the foothills of the Santa Ana Mountains and San Joaquin Hills. Second, thickness of the water-bearing alluvium increases dramatically from Irvine to Orange County across this boundary. Third, permeability of the water-bearing alluvium increases significantly from Irvine to Orange County – the percentage of clay within sediments is much higher within the Irvine management zone. Lastly, the amount of groundwater flow crossing this boundary is relatively small. This is shown by the groundwater elevation contour maps (see Figure 3-19) and in groundwater models constructed by OCWD (G. Woodside, pers. comm., 1999).

· Pacific Ocean to the west. This boundary is drawn along the shoreline. The Newport- Inglewood Fault Zone parallels the coast and has uplifted the impermeable bedrock to shallow depths, creating a natural barrier to seawater intrusion. However, groundwater production within the Orange County and Irvine management zones has lowered groundwater levels and created a hydraulic gradient from the Pacific Ocean toward the coastal aquifers.

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Management Zone: La Habra

Recharge

· Infiltration of flow within the unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock hills.

· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows southwestward from the flanks of the Chino Hills (recharge areas) toward the Coyote Hills. Groundwater in the east flows through a gap in the Coyote Hills into the Orange County management zone, while groundwater in the west flows north of the Coyote Hills into the Central Basin (see Figures 3-18 and 3-19). Discharge

· Groundwater production.

· Underflow to the Orange County management zone and the Central Basin. Boundaries

· Chino Hills the northeast. The Chino Hills border the La Habra management zone in the northeast. These hills are primarily composed of impermeable sedimentary bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Coyote Hills and flow system boundaries with the Orange County management zone to the south. The Coyote Hills are primarily composed of impermeable bedrock and separate the La Habra and Orange County management zones. However, the alluvium is continuous between the management zones in two areas. Groundwater within La Habra flows southward through a bedrock gap between the West Coyote Hills and the East Coyote Hills into the Orange County management zone. The management zone boundary is drawn at the narrowest point in this bedrock gap. To the east of the Coyote Hills, a flow system boundary exists between the La Habra and Orange County management zones. The management zone boundary is drawn from the eastern tip of the Coyote Hills to the Chino Hills in the northeast. Comparison of groundwater elevation maps show that groundwater west of this boundary flows to the north of the Coyote Hills in the La Habra management zone, while groundwater east of this boundary flows to the south of the Coyote Hills in the Orange County management zone (William R. Mills & Associates, 1987).

· Orange County/Los Angeles County line to the northwest. This is a political boundary that is unrelated to groundwater hydrology. Groundwater flows across this boundary, generally from the La Habra management zone into the Central Basin.

Management Zone: Santiago

Recharge

· Infiltration of flow within the Santiago Creek channel.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills.

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· Deep percolation of precipitation and returns from use. Groundwater Flow

· Groundwater generally flows northwestward within the alluvium underlying Santiago Creek, following the direction of flow within the creek. However, little well data was available to analyze the groundwater hydrology of the Santiago management zone. Discharge

· Groundwater production.

· Discharge to Santiago Reservoir and Irvine Lake.

· Evapotranspiration where groundwater along the creek is near the ground surface.

· Underflow to the Orange County management zone through a narrow bedrock gap downstream of Irvine Lake. Boundaries

· Bedrock mountains and hills the northeast. The foothills of the Santa Ana Mountains surround Santiago Creek. These mountains and hills are composed primarily of impermeable sedimentary bedrock. The management zone boundary is drawn along the geologic contact between the bedrock and the unconsolidated alluvium.

· Bedrock constriction along Santiago Creek. Downstream of Irvine Lake (and Villa Park Dam), the Santiago Creek canyon widens and Santiago Creek flows onto the main coastal plain. The boundary between the Santiago and Orange County management zones is drawn across the mouth of the narrow canyon. Groundwater within the alluvium in the Santiago management zone can flow across this boundary and recharge the aquifers within the Orange County management zone.

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4. REGIONAL TDS AND NITROGEN IN GROUNDWATER

4.1 Objective

The objective of Task 4 was to develop point statistics at wells that would represent ambient conditions for nitrate and TDS in groundwater for an historical period and for the current period. [Webster’s defines ambient as the “surrounding atmosphere or environment.” In the context of this study, ambient nitrate and TDS refers to concentrations that are representative of a given volume of groundwater for a given period.] The computed statistics are intended to account for variability resulting from sampling error, analytical error, hydrological/climatic events, and non-homogeneous hydrogeological properties. The point statistics were then used to develop regional estimates of nitrate and TDS in groundwater. Historical and current ambient conditions for each management zone were derived from these regional estimates in Task 5.

4.2 Procedure for Estimating Regional Water Quality

The original procedure for estimation of regional TDS and nitrogen in groundwater is described in the Phase 1B Final Technical Memorandum for Task 3.1 Define Points of Compliance and Management Areas and Task 3.2 Describe Methods to Define Ambient Water Quality, February 1998 (Mark J. Wildermuth, 1998).

4.2.1 Principal Changes to Original Procedure

The TIN/TDS Task Force voted on April 27, 1999 to slightly revise the methodology used to compute the ambient water quality for both historical (objective-setting) and current (compliance) periods. The principal changes were codified in Change Order 2 to Task Order No. 1998-W020-1616-03, dated May 5, 1999. The principal changes to the original procedure are the following:

· formal adoption of mean plus “t” times the standard error of the mean (where “t” is Student’s t) as the statistic that will be computed and contoured for both data sampling periods;

· formalized data sampling period at 20 years:

· 1954 to 1973 for historical ambient water quality, and

· 1978 to 1997 for current ambient water quality;

· eliminated consideration of any trends in the data (climatic or time-trending). The standard error of the mean (SEM) quantifies how accurately the true population mean is known. The standard error of the mean is calculated with the following formula:

s SEM = x n

where sx = standard deviation n = number of observations

Standard deviation is a measure of the dispersal or uncertainty in a random variable and is the square root of sample variance.

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Mathematically, the definition of standard deviation for a random variable X is:

SD = E[(X - E(X )2 ]

where E() signifies an expected value.

4.2.2 Procedure for Estimating Regional Water Quality Used in this Study

Step 1. Develop Updated Boundary Map for Management Zones (described in Section 3)

· Defined boundaries of groundwater subbasins and significant flow systems. The subbasin and flow system delineations were used to delineate management zones. The management zones were reviewed and approved by the Task Force as part of Task 3.

· Reviewed reports and acquired data to delineated aquifer geometry in regions considered to have multiple, layered aquifers. These regions include the Orange County groundwater basin, a portion of the Chino groundwater basin, and the so-called Bunker Hill Pressure Zone. Step 2. Develop Water Quality Point Statistics (for TDS and Nitrate) at Wells in the Watershed

· Reviewed TDS and nitrate time histories. The TDS and nitrate histories for all wells used in developing the estimate of ambient water quality are provided in Appendix A. Each time history includes an accumulated departure from the mean (ADFM) curve. The ADFM curve is useful in characterizing the occurrence and magnitude of wet and dry climatic periods. Negatively sloping segments (trending down to the right) in ADFM curves indicate dry periods; and positively sloping segments (trending up to the right) indicate wet periods. The format of the files in Appendix A is Adobe Acrobat pdf on compact disk (CD). Each CD includes an installation file for Adobe Acrobat Reader.

· Defined data sampling periods. For historical ambient water quality, the data sampling period is January 1, 1954 to December 31, 1973. For current ambient water quality, the data sampling period is a 20-year period ending in the calendar year with the latest complete set of data. As of the date of this technical memorandum, this period is January 1, 1978 to December 31, 1997. Current ambient water quality will be computed as a rolling 20-year average. Future ambient water quality determinations (beyond 1978 to 1997) are not included in the scope of work for the existing contract.

· Applied appropriate statistical tests for normality and outliers. The assumption of the “mean + t*standard error of the mean” approach is that the data are normally distributed or that a transformation can approximate a normal distribution. The use of the Shapiro-Wilk test for both normality and outlier testing was recommended and adopted by the Task Force at the June 15, 1999 meeting. Shapiro and Wilk (1965) developed a test for normality based on normal order statistics. In the Shapiro-Wilk test, a value for the variable, W, is calculated with the formula below. The calculated value of W is then compared with a critical W found in reference tables (e.g., Gibbons, 1994).

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2 æ n ö çåai,n × xi ÷ è i=1 ø W = n 2 å(X i - X avg ) i=1

where: ai,n = coefficients based on the order of the observation, i, and the number of observations, n. (see for example, Gibbons [1994]). th Xi = i observation

Xavg = mean of n observations

A second series of data quality tests were conducted based on the results of general mineral analyses, if data were available. These tests are describe in Standard Methods for the Examination of Water and Wastewater (Greenberg et al., 1992): 1030 F. Checking Correctness of Analyses.

1. Anion-Cation Balance cations - anions % difference =100× å å åcations +åanions with the following acceptance criteria:

Anion Sum (milliequivalents per liter [meq/L]) Acceptable % Difference 0 – 3 ±0.2 meq/L 3 – 10 ±2% 10 - 800 ±2-5%

2. Measured TDS = Calculated TDS measured TDS 1.0 < <1.2 calculated TDS where:

calculated TDS = 0.6 (alkalinity) + Na + K + Ca + Mg + Cl + SO4 + SiO3 + NO3 + F

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3. Measured EC and Ion Sums 0.9× EC <100× anion (or cation) sum, meq / L <1.1× EC

4. TDS to EC Ratios measured TDS 0.55 < < 0.7 EC

and

calculated TDS 0.55 < < 0.7 EC

· If a well had more than one observation of TDS or nitrate per calendar year, the values were averaged prior to computing the statistics. Only one value per year – the annual average – was used in the computation of ambient water quality.

· Computed the following statistics for both TDS and nitrate: mean, standard deviation, standard error of the mean, and mean plus t times the standard error of the mean. Mean plus t times the standard error of the mean is the statistic that was plotted and used to define historical and current ambient water quality. The one-tailed t-values for 85 percent probability based on the degrees of freedom calculated from the number of observations in a given well in a given period were determined using MS Excel functions and checked against reference tables. Step 3. Estimate Regional TDS and Nitrate in Groundwater

· For both TDS and nitrate, mapped the location of wells where statistics have been computed. These locations were annotated with the computed statistic. In addition, wells with mean values (but where statistics could not be computed [e.g., less than the required three data points]) were also plotted. For each groundwater basin, the following maps were developed:

· TDS statistic – historical ambient (1954 to 1973)

· TDS statistic – current ambient (1978 to 1997)

· Nitrate statistic – historical ambient (1954 to 1973)

· Nitrate statistic – current ambient (1978 to 1997)

· For regions with multi-layered aquifers, well construction data was compared to the hydrostratigraphy developed in Step 1 to identify which aquifers are tributary to each well. The water quality maps listed above were developed for each aquifer.

· Developed and digitized contours of TDS and nitrate statistics. The computed statistics for each period, each aquifer layer (if appropriate), and each water quality constituent were carefully contoured and digitized, taking into account:

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· management zone boundaries;

· ancillary water quality data (mean values). These ancillary water quality data were given less weight when contouring than wells with computed statistics; however, they were used to help in guiding contours in areas where there was a paucity of computed statistics. 4.3 Summary of Ambient Water Quality Statistics

A summary of ambient water quality statistics is provided in Appendix A. The format of this file is a Microsoft (MS) Excel workbook on CD. Having the data in digital format will facilitate searching for specific well statistics. Wells in the table are listed by State Well Number. The fields (columns) in the tables are explained in the following table:

Page Column/Field Explanation WEID Key field. Unique identifier for each well in Santa Ana Watershed State Well State Well Number Number Local Name Local name Total Total number of observations in a given well General Minerals Number of observations in well with general mineral analyses Nitrate Number of observations in well with nitrate analyses Number of Nitrate+GM Number of observations in well with concurrent Observations nitrate and general mineral analyses TDS Number of observations in well with TDS analyses TDS+GM Number of observations in well with concurrent TDS and general mineral analyses Total Number of nitrate analyses in Period 1 (1954 to 1 Observations 1973) Obsv with GM Number of nitrate analyses with concurrent general mineral analyses Raw Data Obsv Rejected Number of analyses rejected due to results of general mineral analyses Retained Obsv Number of analyses retained after general mineral screening Average Average nitrate for Period 1 Nitrate in Standard Standard deviation of nitrate for Period 1 Period 1 Deviation Observations Number of observations after annualization after Annualization Outlier R/N Shapiro-Wilk Outlier Test – Rejected (R) or Not Annualized Data (N) Crit W Critical W for Shapiro-Wilk Test Calc W Calculated W for Shapiro-Wilk Test Observations Number of observations after the outlier test after Outlier Average Average nitrate for Period 1 (annualized data)

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 4 –REGIONAL TDS AND NITROGEN CONCENTRATIONS IN GROUNDWATER

Page Column/Field Explanation Standard Standard deviation of nitrate for Period 1 Deviation (annualized data) Ambient mean plus “t” times the standard error of the Nitrate mean – This is the statistic that is contoured

The table continues with TDS in Period 1, Nitrate in Period 2 (1978 to 1997), and TDS in Period 2. If the table were printed, groups of four pages would constitute all the analyses for a given set of wells. There are 184 total pages in the worksheet.

4.4 Estimation of Regional TDS and Nitrate Concentrations

The ambient water quality statistics provided in Appendix A and described in Section 4.3 were plotted and contoured. These maps are provided in Appendix A as Adobe Acrobat files (.pdf). Each of the water quality maps is E-sized and can be viewed with Adobe Acrobat Reader. This will allow the reader to scroll and zoom in order to read the actual point statistic associated with each well. In addition, the .pdf files can be printed E-size for more traditional viewing. The following table describes the maps that are included in Appendix A:

Nitrate TDS Groundwater Basin Management Zone or (1954- (1978- (1954- (1978- Total Area 1973) 1997) 1973) 1997) Number of Maps Bunker Hill, Non- 1 1 1 1 4 San Bernardino Valley Pressure Areas Pressure Area 2 2 2 2 8 San Jacinto Basins 1 1 1 1 4 Chino-Riverside- Chino 1, 2, 3 3 3 3 3 12 Rialto/Colton Basins Chino 4, Riverside, 1 1 1 1 4 Rialto/Colton Elsinore-Temescal Valleys 1 1 1 1 4 Orange County Basins 2 2 2 2 8 All Basins 44

Also included in Appendix A are ArcView shape files of the water quality contours for all the basins in the watershed. These contours can be brought directly into any ArcView project file or imported into other geographic information system (GIS) platforms. The following self-extracting zip files contain the ArcView Shapefiles of the water quality contours:

· BunkerHill_WQ_73_97.exe

· Chino_WQ_73_97.exe

· Coldwater_WQ_73_97.exe

· Cucamonga_WQ_73_97.exe

· Elsinore_WQ_73_97.exe

· Lytle_WQ_73_97.exe

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· RialtoColton_WQ_73_97.exe

· Riverside_WQ_73_97.exe

· SanJacinto_WQ_73_97.exe

· SanTimoteo_WQ_73_97.exe

· Temescal_WQ_73_97.exe

· Yucaipa_WQ_73_97.exe

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5. COMPUTE TDS AND NITROGEN CONCENTRATIONS FOR MANAGEMENT ZONEs (1973 AND 1997)

5.1 Objective

The objective of Task 5 was to generate estimates of ambient water quality (TDS and nitrate) for individual management zones for a historical period (1954 to 1973) and a current period (1978 to 1997). The work performed in Task 5 utilized the work products of Task 3 and Task 4, which are provided in Appendix A.

5.2 Procedure to Compute Ambient Concentrations (TDS and Nitrate) for Management Zones

The final steps in the development of ambient water quality determinations were to develop a rectangular grid coverage over the watershed, estimate the value of the statistic at each grid cell, compute the volume- weighted statistic for each aquifer in each management zone, and then compute the volume weighted statistics for each management zone. If the management zone contains only one aquifer, the last step is not necessary. The specific steps are outlined below:

· Developed fine rectangular grid. The grid size was the same in each basin and was fine enough so that the resulting ambient quality determinations would not be significantly influenced by grid size. Numerical tests were done to determine the appropriate grid size. The grid size used was 400x400 meters. The grid was created using a Fortran routine and then imported into ArcInfo, where each grid cell was assigned a management zone designation. Where a grid cell was split by a management zone boundary, that grid cell would be assigned parameters based on the apportionment of the grid cell into each management zone (determined by area).

Management Zone Boundary

400 m

400 m

· Computed volume of groundwater in storage in each grid cell for each time period. The groundwater elevation contour maps for Fall 1973 and Fall 1997 (generated in Task 3) were used to calculate volume of groundwater in grid cells for the historic and current periods, respectively. The groundwater elevations for each grid cell were estimated by an automated gridding program that interpolated between contours. The volume of groundwater in a grid cell for a single-layer aquifer is operationally-defined as:

Vi = Ai * (WLi – Bi) * SY th where Vi = volume of groundwater in i grid cell Ai = grid cell area (1600 square meters)

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th WLi = average elevation of groundwater in i grid cell (feet above mean sea level [MSL]) th Bi = average elevation of the effective base of aquifer in i grid cell (feet above MSL) SY = specific yield (essentially a weighting factor)

Water Level

Grid Cell Properties: Specific yield, concentration

Bottom of Aquifer

GIS coverages of specific yield were developed to estimate specific yield at each grid cell. The use of specific yield (as opposed to porosity) causes the computed volume of groundwater to represent the volume that can be pumped, not the actual amount of water in storage.

· Computed volume of groundwater in storage in each layer of a multi-layer aquifer. Groundwater in storage for each layer in a multi-layer aquifer was computed in exactly the same fashion as in a single-layer aquifer. However, the top of a confined aquifer was used to calculate the water in storage if the groundwater level was above the top of the aquifer. The volume of groundwater in storage in each grid cell was then summed.

· Computed volume of groundwater in a management zone. Total volume of groundwater within a management zone was calculated by summing the volume of groundwater in all grid cells within the management zone.

· Estimated value of statistic for each grid cell. The value of TDS and nitrate statistic for each grid cell were estimated by an automated gridding program that interpolated between contours of the statistics.

· Computed volume-weighted statistic for each aquifer in each management zone using the following formula:

1 Cavg = ( ) × å Ci ×Vi VT

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where: Cavg is the average concentration in a management zone VT is the total volume of groundwater within a management zone Ci is the concentration in small control volume i Vi is the volume of water stored in control volume i and with concentration Ci

· Computed volume-weighted statistic for each management zone. If the management zone contains only one aquifer, this step is not necessary. Ambient water quality values for management zones for both periods are shown in Table 5-1. The difference in ambient water quality (current minus historical) was also calculated and included in Table 5- 1. Figures 5-1 and 5-2 show historical ambient water quality for TDS and nitrate, respectively. Computed volume-weighted values for each management zone are depicted in the figures. The figure is also color- coded by class interval:

Historical Ambient Water Quality Class TDS Nitrate Interval (mg/L) (mg/L) 7 >1000 6 700 to 1000 5 500 to 700 >16 4 400 to 500 8 to 16 3 300 to 400 4 to 8 2 250 to 300 2 to 4 1 <250 <2

Figures 5-3 and 5-4 show the difference between current ambient water quality and historical ambient water quality for TDS and nitrate, respectively. Values for each management zone are depicted in the figures along with color-coding by class interval:

Historical Ambient Water Quality Minus Current Ambient Water Quality Class TDS Nitrate Interval (mg/L) (mg/L) 7 >100 >2 6 50 to 100 1 to 2 5 0 to 50 0 to 1 4 -50 to 0 -1 to 0 3 -100 to -50 -2 to -1 2 -500 to -100 -5 to -2 1 <-500 <-5

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5.3 Details Related to Computation of Ambient Concentrations

The methodology described above was the template used to compute ambient concentrations of TDS and nitrate for management zones. In some instances, the methodology was modified to accommodate the available data. In some instances, where data availability was not sufficient, ambient concentrations were not computed for those management zones. The following is a list of details related to the computation of ambient concentrations for management zones:

· For the Orange County groundwater basin, the shallow and principal (middle) aquifers were used in the calculation of ambient water quality. The deep aquifer was not used because relatively few wells produce from this aquifer, water quality data is sparse and, hence, ambient water quality could not be characterized.

· For the Bunker Hill groundwater basin, the shallow and middle aquifers within the so-called Pressure Zone were used in the calculation of ambient water quality. The deep aquifer was not used because relatively few wells produce from this aquifer, water quality data is sparse and, hence, ambient water quality could not be characterized.

· For the Chino groundwater basin, the shallow, middle, and deep aquifers were used in the calculation of ambient water quality within Chino-1, Chino-2, and Chino-3 management zones. The confining units that separate the aquifers in Chino-1, Chino-2, and Chino-3 become thin or “pinch out” within the Chino-4 and Chino-5 management zones and, hence, Chino-4 and Chino-5 were treated as single-aquifer systems in the calculation of ambient water quality.

· OCWD provided groundwater elevation contour maps for the principal (middle) aquifer. However, estimates of groundwater levels in the shallow aquifer were necessary to calculate regional water quality in the shallow aquifer. OCWD staff and WE, Inc. agreed to estimate water levels in the shallow aquifer by using groundwater elevation contours of the principal aquifer in the forebay areas and using the top of shallow aquifer in the pressure areas (i.e. assuming complete saturation of the shallow aquifer in the pressure area).

· For the Orange County groundwater basin, OCWD provided aquifer geometry data from its current groundwater model. In some areas, the model boundary did not extend to the management zone boundaries. As a result, some grid cells did not contain aquifer geometry data and were not used to calculate ambient water quality. In most cases, these grid cells were located at the periphery of the basin where saturated aquifer thickness was small or non- existent.

· The following is a list of management zones where not enough water quality data exists to characterize regional TDS and nitrate in groundwater for the historic period (1954 to 1973):

· Bedford

· Lee Lake

· Warm Springs Valley

· La Habra

· Santiago

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6. COMPLIANCE METRIC FOR THE SANTA ANA RIVER AT PRADO DAM

6.1 Objective

This section presents a review of existing (historical) data to determine if new metrics could be developed that are equally protective of the Orange County groundwater basin and allow more upstream reclamation. The analysis of existing data focused on identification of correlations between surface water quality in the Santa Ana River (SAR) at below Prado and groundwater quality at wells in the Orange County groundwater basin.

6.2 Existing August-Only Metric

The quality of SAR water is function of the quality and quantity of the various sources of water to the SAR (RWQCB, 1995). The Santa Ana River Watermaster (Watermaster) has divided the discharge in the SAR into three components consisting of storm flow, base flow and non-tributary flow. Storm flow is discharge caused by direct runoff of precipitation and usually occurs in December through April. With some exceptions, the TDS and TIN of storm flows are generally very low – the exceptions being runoff from agricultural lands. Base flow consists of rising groundwater and the direct discharge of recycled water to the SAR and its tributaries. The TDS and TIN of rising water is not well characterized, but is significantly higher in concentration than storm water. The TDS and TIN of the recycled water discharges varies among the treatment plants. Non-tributary flows primarily consist of the direct discharge of imported water to the SAR and its tributaries. The Watermaster also distinguishes other non-tributary flows, such as groundwater that is pumped in the San Bernardino area and discharged to the SAR upstream of Prado and treated groundwater from the Arlington Desalter that is discharged to the SAR upstream of Prado.

The RWQCB has established TDS and TIN objectives for Reaches 2 and 3 of the SAR (Figure 6-1). Reach 3 runs from Prado Dam to the Mission Boulevard bridge in Riverside. The TDS and TIN objectives for Reach 3 are 700 mg/L and 10 mg/L, respectively, for base flow measured in the SAR below Prado in August. Non-point surface inflows (storm water and urban nuisance flows) and agricultural surface returns to the SAR are managed by Best Management Practices where appropriate. The quantity and quality of base flow are most consistent in August (RWQCB, 1995). The RWQCB believes that the dominant source of water during August is recycled water discharged to the SAR. The purpose of the August-only objective is to verify the wasteload allocation and to determine if assimilative capacity exists (RWQCB, 1995). The RWQCB reviews water quality data from OCWD and the USGS, and conducts its own sampling program in the SAR at below Prado in August. The RWQCB uses water quality models to develop wasteload allocations for the recycled water dischargers to the SAR. These models do not include storm flows. Storm flows have increased due to urbanization in the SAR watershed upstream of Prado Dam. Urban storm water runoff has been shown by the Chino Basin Watermaster (Mark J. Wildermuth, 1998b) to be very low in TDS and TIN – generally less than 100 mg/L and 1 mg/L, respectively.

Reach 2 runs from 17th Street in Santa Ana upstream to Prado Dam. Surface water discharge from Reach 3 flows into Reach 2. The TDS objective for Reach 2 is 650 mg/L measured in the SAR below Prado – the same location that compliance with the Reach 3 objective is determined. The TDS objective for the Santa Ana Forebay subbasin in the 1995 Basin Plan is 600 mg/L. In contrast to Reach 3, the RWQCB computes a five-year moving average of TDS for the SAR below Prado based on Watermaster’s annual average estimate of TDS in the total flow (excludes non-tributary discharges and groundwater that is pumped and discharged to the SAR upstream of Prado Dam). The use of this moving average allows the effects of wet and dry years to be smoothed out over the five-year period (RWQCB, 1995). The Basin Plan does not have a TIN objective for Reach 2. The Basin Plan assumes that TIN compliance in Reach 3 is protective of Reach 2.

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The TDS objectives for Reaches 2 and 3 are measured at the same physical location – the SAR below Prado dam. The Reach 3 objective uses a portion of the data used to measure compliance for Reach 2 for TDS. The watershed upstream of Prado Dam is rapidly urbanizing and the storm runoff and recycled water discharges to the SAR have increased significantly. The increased use of recycled water upstream of Prado could lead to higher TDS concentrations in the SAR below Prado Dam in the summer. This would occur because the upstream agencies will preferentially reuse their lower TDS recycled water and will continue to discharge their higher TDS recycled water to the SAR. The following questions will need to be answered: 1. Does managing Reach 3 to 700 mg/L in August protect the MUN beneficial use in the existing Orange County Forebay subbasin and the proposed Orange County management zone? 2. Should the increasing storm water component of surface flow be used to offset the TDS in recycled water discharges upstream of Prado?

The answer to the first question is yes based on review of historical data presented herein. The second question is a policy question that depends on two technical findings:

· The flow-weighted TDS and TIN concentration of all sources of recharge in the Orange County management zone must be less than or equal to its respective objectives.

· The groundwater basin must be able to buffer the temporal fluctuations in SAR recharge quality such that impairment does not occur at any well in the basin. The first finding may be done in Phase 2B or some other subsequent effort. The second finding is discussed in the remainder of this section.

6.3 Water Quality and Quantity at and Below Prado

6.3.1 Surface Water at Below Prado

Surface water flow and TDS and TIN concentration of the SAR are measured at a point just below Prado Dam (Figure 6-1). The USGS maintains a gauging station at this location to measure instantaneous flow and, in 1973, installed a water quality recorder to obtain continuous measurements of specific conductance. Surface water grab samples are taken by the USGS and analyzed for both specific conductance and TDS to establish a mathematical relationship between the two parameters, which is used to convert the continuous record of specific conductance to a daily average TDS concentration time history. Other agencies, including OCWD and the RWCQB, also collect grab samples at this location to measure TIN and TDS concentration of the SAR. The above data was collected, compiled, and analyzed in an effort to characterize the time history of surface water quality of the SAR at below Prado.

Figure 6-2a illustrates the time history for instantaneous surface water flow and TDS of the SAR at below Prado from 1950 through 1998. Note the distinct inverse correlation between flow and TDS concentration. During storm flow conditions, runoff dilutes the base flow TDS reducing the TDS concentration in the total flow sometimes to below 200 mg/L.

Figure 6-2b is a time history of TDS and components of flow of the SAR at below Prado for the period 1950 to 1998. Flow is displayed as an annual value that is sub-divided based on source component (i.e. storm flow, base flow, etc.). From water year 1969-70 to 1997-98, flow and source component breakdown was obtained from Santa Ana River Watermaster annual reports. Prior to 1969-70, flow and source component breakdown was obtained from a report prepared for use in Orange County v. City of Chino, et al (Leeds, Hill and Jewett, 1969). Comparison of TDS and source components of flow provides insight to TDS trends in SAR water at below Prado.

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TDS in SAR water at below Prado ranged from a maximum of 1,160 mg/L on January 29, 1970 to a minimum of 109 mg/L on February 20, 1978. However, Figure 6-2b shows that the 1-year moving average of TDS fluctuated between 450 to 800 mg/L. Also note in Figure 6-2b that the August-only TDS concentration at below Prado, as measured by the RWQCB, is typically greater than or equal to moving TDS averages. A notable exception occur in 1997 when State Water Project water released upstream of Prado in August decreased TDS concentrations in the SAR.

The major TDS trends in Figures 6-2a and 6-2b are (1) generally increasing TDS concentrations from 1950 to about 1970, followed by (2) generally decreasing TDS concentrations from 1970 to 1998. These trends may be explained by the following factors:

· A dry climatic period during the 1950s and 1960s that resulted in base flow and Colorado River Water discharges to the SAR at Pedley (for purposes of groundwater recharge in Orange County in the 1950s) as the major components of flow.

· Adoption of the Basin Plan in the early 1970s, setting TDS limitations on wastewater discharges.

· Availability of relatively low-TDS State Water Project (SWP) water in the early 1970s for water supply and groundwater recharge.

· A wetter climatic period from 1978 to the present, which increased the relatively low-TDS storm flow component of SAR flow. Shorter-period TDS fluctuations also are readily apparent in Figures 6-2a and 6-2b, and include:

· A depression in TDS concentrations during the mid-1970s, due to the purchase of low-TDS State Water Project water by OCWD and its subsequent release to San Antonio Creek upstream of Prado.

· Prolonged periods (~2 years) of relatively high TDS following extreme wet years (e.g. 1969, 1980, 1993).

· Seasonal decreases in TDS due to increased storm water flow. Figures 6-3a and 6-3b are similar to Figures 6-2a and 6-2b, but characterize TIN at below Prado instead of TDS. Figure 6-3a illustrates the time history for instantaneous surface water flow and TIN of the SAR below Prado from 1950 through 1998. Figure 6-3b is a time history of TIN and components of flow of the SAR at below Prado for the period 1950 to 1998. Note the absence of TIN data for the SAR at below Prado prior to 1969.

TIN in SAR water below Prado ranged from below detection limits to a maximum of 18.7 mg/L on October 31, 1977. However, Figure 6-3b shows that the 1-year moving average of TIN fluctuated between about 4 to 11 mg/L.

The major TIN trends in Figures 6-3a and 6-3b are: (1) generally increasing TIN concentrations from 1979 to about 1991, followed by (2) generally decreasing TIN concentrations from 1991 to 1998. In contrast, TDS in the SAR at below Prado generally decreased during the 1982-1998 period. The TIN trends in SAR water below Prado may be explained by the following factors:

· Increasing effluent discharges from wastewater treatment facilities upstream of Prado from 1979 to 1991.

· Decreasing TIN concentrations in effluent discharges from wastewater treatment facilities upstream of Prado during the 1990s.

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· A wetter climatic period from 1993 to 1998.

6.3.2 Groundwater Recharge

After exiting Prado, SAR water flows down the Santa Ana Canyon and percolates to the shallow, narrow alluvial aquifer underlying the river (Figure 6-1). Groundwater flow parallels the river in the Santa Ana Canyon and, ultimately, is produced by wells or discharged as underflow to the main Orange County groundwater basin (the Orange County management zone as defined in Task 3).

At the mouth of the Santa Ana Canyon, the SAR discharges onto the forebay region of the Orange County management zone in Anaheim. The Orange County management zone is recharged primarily in the forebay region by various sources listed below:

· Infiltration of flow within the SAR channel north of Katella Avenue. These flows include:

· runoff from urban, agricultural and undeveloped areas;

· upstream discharges from wastewater treatment facilities,

· and upstream discharges of imported water.

· Infiltration of SAR water at OCWD recharge facilities located off-river in Anaheim and along Santiago Creek.

· Direct discharge and infiltration of Colorado River Aqueduct (CRA) water at Anaheim Lake, Miller, and Kraemer recharge basins.

· Infiltration of flow within other unlined stream channels overlying the management zone.

· Underflow from the saturated alluvium and fractures within the bordering bedrock mountains and hills.

· Groundwater injection at the Talbert Gap and Alamitos Barrier to inhibit seawater intrusion.

· Underflow through a bedrock gap in the Coyote Hills from the La Habra management zone.

· Deep percolation of precipitation and returns from use. Volumetrically, the most significant recharge to the Orange County groundwater basin occurs at OCWD recharge facilities along the SAR and Santiago Creek (OCWD-SAR recharge facilities). A tabular and graphical representation of the volumes and sources of water recharged at the OCWD-SAR recharge facilities is shown in Table 6-1 and Figure 6-4, respectively, for the period 1950 to 1998. Note that CRA water was the dominant source of recharge from about 1957 to 1971. Annual average TDS concentrations of CRA water during this period ranged from 609 to 815 mg/L, and averaged 710 mg/L. SAR water was the most significant source of recharge from about 1971 to the present. Flow-weighted annual average TDS concentrations of SAR water during this period ranged from 462 to 732 mg/L, and averaged 588 mg/L. The volumetric increase in recharge of SAR water is due to:

· the expansion and improvement of OCWD-SAR recharge facilities;

· the availability of imported State Water Project water at a discharge point upstream of Prado Dam;

· the increase of base flow in the SAR largely due to increased discharges from upstream wastewater treatment facilities, and

· a generally wetter climatic period.

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6.3.3 Fate of Recharge Water

As discussed previously, a portion of Task 2.1 is to determine if a causative relationship between water quality in the SAR at below Prado and groundwater in the Orange County management zone can be developed. Groundwater in the forebay region of the Orange County management zone is recharged by a variety of sources (see above, Section 6.3.2), but primarily SAR and imported water at OCWD-SAR recharge facilities:

In order to begin to parse the causative effects of various sources of recharge, one needs to know which wells are impacted by recharge at OCWD-SAR recharge facilities to a greater degree than other wells. Various methods for determining the area impacted by recharge at OCWD-SAR recharge facilities were employed:

· review of historical groundwater elevation maps;

· review of tritium-helium age dating of groundwater (Clemens-Knott et al., 1998); and

· an analysis of general water character. Figure 6-1 shows an approximate area where underlying groundwater was recharged less than 25 year ago at OCWD-SAR recharge facilities. This area was delineated based on tritium-helium age dating of groundwater (Clemens-Knott et al., 1998). Groundwater elevation contours are also shown in this figure.

A third method was used to corroborate the delineation based on tritium-helium age dating of groundwater. The water character index (WCI) is a unitless parameter that provides a numerical estimation of water character. WCI can be used to assess the ionic distribution of constituents in a water sample. This is analogous to a trilinear or Piper diagram, which is a graphical means of displaying the ratios of the principal ionic constituents in water (Piper, 1944; Watson and Burnett, 1995). Water character is defined by the following equation:

æ Ca + Mg ìCO + HCO üö çì ü 3 3 ÷ WCI =100×çí ý + í ý÷ èî Na + K þ î Cl + SO4 þø where Ca, Mg, et cetera, are expressed in terms of milliequivalents per liter (meq/L) rather than milligrams per liter (mg/L). The first term on the right hand side of the equation is the ratio of divalent to monovalent cations and the second term on the right hand side of the equation is a ratio of carbonate character to chloride/sulfate character. The utility of the WCI method, compared with a Stiff or Piper/trilinear diagram, is that many data points can be plotted as time histories for a given well or surface water station. The points can also be plotted to show areal and spatial distributions of water character. In addition, the WCI method can be used to provide a quantitative estimate of mixing of source waters with differing WCIs. WCI as a function of time is shown on Figure 6-5 for

· the Santa Ana River at below Prado;

· CRA water (Lake Mathews);

· SWP water (Lake Silverwood);

· groundwater affected by recent recharge (based on the tritium-helium age dating data); and

· groundwater not affected by recent recharge. The WCI for SWP water responds dramatically to climatic changes (cf. the ADFM curve shown in Figure 6-5), while the WCI for CRA water is much more stable. The WCI for SAR water at below Prado shows

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some climatic variability, especially in 1969 and 1978. Table 6-2 summarizes the averages, standard deviations, and ranges of WCI for source waters and for groundwater

Based on these results, it is possible to delineate areas where groundwater is affected by recharge at OCWD-SAR recharge facilities. Figure 6-6 shows the areal distribution of WCI for the Orange County groundwater basin. The class intervals were defined based on historical values of WCI, listed in Table 6- 2. Note that in Figure 6-6, (i) most of the groundwater samples represent a mixture of water from two or more sources; and (ii) the values plotted represent average values for a given well over time.

Range WCI Range Probable Source Orange County MZ: seawater intrusion Irvine MZ: mineralization of local alluvium and unconsolidated bedrock 1 < 149 Other MZs: mineralization of local alluvium, returns from use, or local recharge of tributary sources high in sodium chloride/sulfate character (low WCI) Near OCWD-SAR recharge facilities: CRA, SWP water 2 150 to 199 Other areas: Mixture of Range 1 water with other local groundwater Near OCWD-SAR recharge facilities: SAR water or a mixture of Range 2 water 3 200 to 249 with other local groundwater Groundwater affected by recent recharge; mixtures of CRA, SWP, SAR, and local 4 250 to 349 groundwater. 5 350 to 599 Groundwater not affected by recent recharge. 6 > 600 Native Groundwater

Figure 6-6 also depicts an approximate area where underlying groundwater was recharged less than 25 year ago at OCWD-SAR recharge facilities, based on tritium-helium age dating of groundwater (Clemens-Knott et al., 1998). Figure 6-6, thus demonstrates the corroboration of the tritium-helium age dating data by the WCI analysis.

6.3.4 TDS and TIN in Groundwater

The distribution of TDS and TIN concentrations within the principal aquifer (OCWD Model Layer 2) of the Orange County groundwater basin is depicted in Figures 6-7 through 6-10. Figures 6-7 through 6-8 display TDS and TIN average values, respectively, for wells over various three-year periods that correspond to various climatic conditions. Figures 6-9 and 6-10 are concentration contour interval maps of TDS and TIN, respectively, for a historical (1954-73) and a current (1978-97) period. The latter figures were constructed from the ambient water quality maps generated for Task 4 (see Section 4 and Appendix A).

In the above-mentioned figures that depict TDS distributions, note the elevated TDS concentrations (>600 mg/L) underlying the area west and southwest of the OCWD-SAR recharge facilities. This area is downgradient of these facilities, and coincides spatially with groundwater of recent age and of low water character values – indicating an imported and/or recent SAR component of recharge.

[Note: The term “recent” in reference to the age of groundwater is used in an approximate sense, and corresponds to water recharged at OCWD-SAR recharge facilities after about 1950. Figures 2-1 displays an approximate area where underlying groundwater was recharged less than 25 year ago at OCWD-SAR recharge facilities based on tritium-helium age dating of groundwater (Clemens-Knott et al., 1998).

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Groundwater of “recent” age, therefore, would underlie this area as well as areas slightly downgradient (west and southwest) of this area.]

In contrast, the aquifer underlying the central and coastal portions of the basin contains groundwater with relatively low TDS concentrations (< 600 mg/L). This area also is downgradient of OCWD-SAR recharge facilities, but coincides spatially with groundwater of relatively older age (>50 years old) and of high water character values – indicating that groundwater is un-impacted by imported and/or recent SAR recharge.

In Figure 6-9, comparison of TDS distributions in the historical (1954-73) and current (1978-97) periods shows a general decrease in TDS concentration near and downgradient of OCWD-SAR recharge facilities. This apparent decrease in TDS over time is the result of the following factors:

· Decreased recharge of relatively high-TDS CRA water at OCWD-SAR recharge facilities (Figure 6-4),

· Generally lower TDS concentrations in SAR water during the current period (Figures 6-2a and 6-2b),

· Increased recharge of SAR water at OCWD-SAR recharge facilities (Figure 6-4), and

· Differences in the data sets used to map TDS distributions in groundwater. A time history of combined, flow-weighted annual TDS concentration of all waters recharged at OCWD- SAR recharge facilities (SAR water and CRA water) is displayed in Figure 6-11. Note that annual TDS concentrations of recharged water during the historical period (1954-73) are generally above 600 mg/L and averaged 665 mg/L. Annual TDS concentrations of recharged water during the current period (1978- 97) averaged 585 mg/L. These data corroborate the observation that TDS in groundwater near and directly downgradient of OCWD-SAR recharge facilities has decreased from the historical to the current period.

Time histories of TDS and TIN for each well in the Orange County groundwater basin were plotted against 182-day averages of TDS and TIN at below Prado and the accumulative departure from mean precipitation (ADMF) curve. For TDS time histories, annual average TDS of CRA water was also plotted. These time histories are included in Appendix A in Adobe Acrobat (pdf) format.

The TDS and TIN time histories were analyzed to identify wells that respond to water quality trends in the SAR at below Prado. Figures 6-1 and 6-12 display an approximate area where underlying groundwater was recharged less than 25 year ago at OCWD-SAR recharge facilities. This area was delineated based on tritium-helium age dating of groundwater (Clemens-Knott et al., 1998). Analysis of TDS time histories focused on wells located within this area.

Within this area of 25-year-old groundwater, the wells that were analyzed in detail for this study are listed in the following table:

State Well Number Local Name WE_ID 3S/9W-31Q1 KBS-2 10226 3S/9W-32F2 ABS-1 5607 3S/9W-32K6 A-30 2585 3S/9W-32K7 A-31 2587 3S/9W-32K8 A-32 2589

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State Well Number Local Name WE_ID 3S/9W-32L1 A-43 101 3S/9W-32M1 A-44 106 3S/9W-32P4 A-28 2591 3S/9W-32P5 A-42 102 3S/9W-33K1 YLWD-5 2593 3S/9W-33K3 YLWD-9 2595 3S/9W-33K4 YLWD-7 2597 3S/9W-33K5 YLWD-12 2599 3S/9W-33K6 YLWD-10 2601 3S/9W-33K7 YLWD-1 2603 3S/9W-34N1 YLWD-15 1521 3S/10W-35K3 F-10 7000 4S/9W-2D1 OCWD-HG1 2858 4S/9W-4A1 WBS-3 10154 4S/9W-4C2 WBS-2A 10233 4S/9W-4G1 YLWD-11 531 4S/9W-4M3 WBS-4 6415 4S/9W-5B3 AM-5A 2733 4S/9W-5K2 SAR-7 6168 4S/9W-5M4 AM-6 552 4S/9W-5Q2 SAR-8 6190 4S/9W-6H2 AMD-1 5623 4S/9W-6K2 AM-13 554 4S/9W-7B2 SAR-6 6138 4S/9W-7N1 SAR-1 5961 4S/10W-11Q2 A-29 889 4S/10W-12B3 AMD-2 5653 4S/10W-13R1 SAR-2 6001 4S/10W-14D2 A-22 1058 4S/10W-14F1 AMD-5 7318 4S/10W-14H2 A-15 1057 4S/10W-14M1 A-25 1056 4S/10W-15B5 A-34 1055 4S/10W-17H1 A-35 891 4S/10W-17J2 A-10 893 4S/10W-17L2 A-18 895 4S/10W-1F1 A-26 537 4S/10W21L1 A-36 1054 4S/10W-3P1 A-6 1069 4S/10W-3P1 A-6 1069 4S/10W-3P2 A-7 1068 4S/10W-3R3 AMD-3 6433 4S/10W-4Q2 A-20 539 4S/10W-4R1 F-3 1067 4S/10W-4R3 F-4 1066

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State Well Number Local Name WE_ID 4S/10W-4R4 F-6 1065 4S/10W-4R5 F-5 1064 4S/10W-4R7 F-7 1063 4S/10W-4R8 F-8 1062 4S/10W-9B2 A-14 1059 4S/10W-9B3 A-23 887 4S/10W-9B5 AMD-4 7101

It is important to note that a time lag exists between the time history of SAR water quality at below Prado and the time history of water quality at a well receiving recharge of such water. OCWD, in conjunction with other entities, has conducted a number of investigations downgradient of its recharge facilities to determine flow paths, travel times and mixing ratios of recharged waters. The results of these studies were reviewed and used to estimate reasonable lag times between SAR and groundwater time histories.

6.3.4.1 TDS AT WELLS

Representative examples of TDS time histories of the wells analyzed were re-plotted on an expanded time-scale (1950 to 1999) and with 1-year to 5-year moving TDS averages of SAR water at below Prado. These TDS time histories are shown in Figures 6-13a and 6-13b. Figure 6-13a displays TDS time histories of two wells that are located about 3-4 miles downgradient of the OCWD-SAR recharge facilities, and likely receive SAR water several years after recharge. In this scenario, a significant time lag will exist between TDS trends in SAR water and well water, if indeed such correlations exist. Figure 6- 13b displays TDS time histories of two wells that are located close to the OCWD-SAR recharge facilities, and likely receive SAR water quicker than the wells located 3-4 miles downgradient (i.e. shorter lag time). The well locations are shown on Figure 6-12 and labeled by State Well Number.

Well A-22 (04S/10W-14D02) is located at about the center of the 25-year-old groundwater outline in Figure 6-12. This well is perforated from 378-421 feet-bgs, which is within the principal aquifer and presumably receives groundwater recharged at OCWD-SAR recharge facilities. TDS of groundwater at well A-22 has ranged between 550-864 mg/L and averaged 686 mg/L over the period 1969 to 1998 (Figure 6-13a). The TDS time history of well A-22 shows decreasing TDS from concentrations greater than 750 mg/L in the early 1970s to less than 600 mg/L in the early 1980s. Since the early 1980s, TDS at well A-22 has been relatively constant between 600-700 mg/L.

The decreasing TDS trend at well A-22 in the early 1980s may correspond to recharge of relatively low- TDS SWP water by OCWD in the mid-1970s. The observation that TDS concentrations since the early 1980s never returned to levels higher than 700 mg/L (with the exception of an anomalously high concentration of 864 mg/L in 1992) suggests that the decreasing TDS trend in SAR water since the early 1970s is influencing TDS in well A-22.

Well F-4 (04S/10W-04R03) is located at the northwest corner of the 25-year-old groundwater outline in Figure 6-12. This well is perforated from 315-405 feet-bgs, which is within the principal aquifer and presumably receives groundwater recharged at OCWD-SAR recharge facilities. TDS of groundwater at well F-4 has ranged between 557-845 mg/L and averaged 675 mg/L over the period 1956 to 1998 (Figure 6-13a). The TDS time history of well F-4 shows increasing TDS concentrations from about 600 mg/L in the late 1950s to a maximum of 845 mg/L in the early 1970s. A data gap exists in the 1970s. From the early 1980s to 1998, TDS at well F-4 has been relatively constant between 650-750 mg/L.

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The increasing TDS trend at well F-4 from the 1950s to the 1970s follows the increasing trend in SAR water during the same period. However, the trends are likely unrelated given that well F-4 is about 4 miles from the OCWD-SAR recharge facilities and that a travel time of several years is probable. Other TDS trends at well F-4 that correspond to TDS trends of SAR water are not apparent.

Well YLWD-11 (04S/09W-04G01) is located adjacent to the SAR and other OCWD-SAR recharge facilities (Figure 6-12). This well is perforated from 115-514 feet-bgs, and presumably receives groundwater recharged at OCWD-SAR recharge facilities. TDS of groundwater at well YLWD-11 has ranged between 462-858 mg/L and averaged 676 mg/L over the period 1956 to 1997 (Figure 6-13b). The TDS time history of well YLWD-11 shows increasing concentrations from about 650 mg/L in the 1950s to greater than 750 mg/L in the late 1960s. From the early 1970s, TDS decreased from concentrations greater than 750 mg/L to less than 600 mg/L in the late 1970s. Since the late 1970s, TDS at well YLWD- 11 has been relatively constant between 600-725 mg/L.

In general, the TDS trends at well YLWD-11 followed the TDS trends in the SAR with little or no time lag. However, the apparent absence of a decreasing TDS trend at well YLWD-11 in the 1990s that corresponds to decreasing TDS in the SAR suggest the existence of additional sources of recharge for well YLWD-11.

Well YLWD-12 (03S/09W-33K05) is located about 0.5 mile north (downgradient) of the OCWD-SAR recharge facilities (Figure 6-12). This well is perforated from 80-498 feet-bgs, and presumably receives groundwater recharged at OCWD-SAR recharge facilities. TDS of groundwater at well YLWD-12 has ranged between 625-876 mg/L and averaged 727 mg/L over the period 1966 to 1998 (Figure 6-13b). The TDS time history of well YLWD-12 shows decreasing TDS from concentrations greater than 800 mg/L in the early 1970s to less than 650 mg/L in the late 1970s. Since the late 1970s, TDS at well YLWD-12 has ranged between 625-775 mg/L with no apparent pattern.

In the 1970s, the decreasing TDS trend at well YLWD-12 followed the decreasing TDS trend in the SAR with a possible time lag of about 2 years. However, the apparent absence of a decreasing TDS trend at well YLWD-12 in the 1990s that corresponds to decreasing TDS in the SAR suggests the existence of additional sources of recharge for well YLWD-12.

The following conclusions are drawn from analysis of TDS time histories of wells downgradient of OCWD-SAR recharge facilities:

· Groundwater sampling typically was not frequent enough to identify trends in groundwater caused by short-term (e.g. seasonal) fluctuations in recharge waters, if indeed such trends existed in groundwater.

· In general, some long-term TDS trends at wells followed similar TDS trends in SAR water. However, these trends are typically subtle, difficult to identify (i.e. may not be identified as trends under a more rigorous statistical analysis), and not always consistent over the entire time history of the well.

· In general, TDS concentration at wells frequently is greater than TDS moving averages in SAR water at below Prado (Figures 6-13b, for example). Mixing with other higher-TDS source waters (e.g. CRA water, returns from use, older SAR water, etc.) may explain this observation.

· Mixing of groundwaters of different ages and of different sources (CRA water recharged at Anaheim Lake, percolation of returns from use and local runoff, etc.), both within the aquifer and within the well column, influences the TDS time histories at wells. This mixing

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phenomenon, even for wells located adjacent to SAR recharge facilities, is documented by OCWD-sponsored groundwater investigations in the forebay area (Clemens-Knott et al., 1998; Davisson et al., 1999).

6.3.4.2 TIN AT WELLS

Representative examples of TIN time histories of the wells analyzed were re-plotted on an expanded time-scale (1950 to 1999) and with the 1-year to 5-year moving TIN averages of SAR water at below Prado. These TIN time histories are shown in Figures 6-14a and 6-14b. [Note: TIN in groundwater is expressed as nitrate-nitrogen, since ammonia and nitrite are typically found at less than detectable concentrations in groundwater]. Figure 6-14a displays TIN time histories of two wells that are located about 4 miles downgradient of the OCWD-SAR recharge facilities, and likely receive SAR water several years after recharge. In this scenario, a significant time lag will exist between TIN trends in SAR water and well water, if indeed such correlations exist. Figure 6-14b displays TIN time histories of two wells that are located close to the OCWD-SAR recharge facilities, and likely receive SAR water quicker than wells 3-4 miles downgradient (i.e. shorter lag time). The well locations are shown on Figure 6-12 and labeled by State Well Number.

TIN of groundwater at well A-22 (04S/10W-14D02, located about 3 miles downgradient of OCWD-SAR recharge facilities) has ranged between 0.7-7.2 mg/L and averaged 3.8 mg/L over the period 1962 to 1998 (Figure 6-14a). The TIN time history of well A-22 shows increasing TIN from concentrations in the 1-3 mg/L range prior to 1978 to the 5-6 mg/L range in the late 1990s. This increasing TIN trend at well A-22 corresponds to increasing TIN in the SAR from the 1970s to the early 1990s, when considered with a time lag of several years.

TIN of groundwater at well F-4 (04S/10W-04R03, located about 4 miles downgradient of OCWD-SAR recharge facilities) has ranged between 0.5-10.2 mg/L and averaged 5.0 mg/L over the period 1956 to 1998 (Figure 6-14a). The TIN time history of well F-4 shows decreasing TIN concentrations from about 8 mg/L in the late 1950s to concentrations below 1 mg/L in the early to mid 1960s. From the late 1960s to the mid 1980s, TIN fluctuated between 2-4 mg/L, although data was relative sparse during this period. During the 1990s, TIN at well F-4 increased and fluctuated between 4-7 mg/L. TIN trends at well F-4 that correspond to TIN trends of SAR water are not readily apparent.

TIN of groundwater at well YLWD-11 (04S/09W-04G01, located adjacent to the SAR and other OCWD- SAR recharge facilities) has ranged between 0.3-8.6 mg/L and averaged 4.6 mg/L over the period 1956 to 1997 (Figure 6-14b). The TIN time history of well YLWD-11 shows relatively constant TIN concentrations between 0-2 mg/L from 1956 to 1971. TIN data for the SAR at below Prado was not available for comparison. From 1971 to 1997, TIN at well YLWD-11 followed the pattern of TIN fluctuations in the SAR with little or no time lag, but at lesser concentrations.

Well YLWD-9 (03S/09W-33K03) is located about 0.5 mile north (downgradient) of the OCWD-SAR recharge facilities (Figure 6-12). This well is perforated from 72-327 feet-bgs, and presumably receives groundwater recharged at OCWD-SAR recharge facilities. TIN of groundwater at well YLWD-9 has ranged between 0.2-5.5 mg/L and averaged 3.8 mg/L over the period 1979 to 1998 (Figure 6-13b). The TIN time history of well YLWD-9 shows almost constant TIN concentration of about 4 mg/L. The apparent absence variation of TIN concentrations at well YLWD-9, while TIN concentrations in SAR water fluctuated widely between about 2-12 mg/L, suggests the existence of additional sources of recharge for well YLWD-9.

Conclusions drawn from analysis of TIN time histories of wells downgradient of OCWD-SAR recharge facilities are similar to conclusions drawn from analysis of TDS time histories discussed above:

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· Groundwater sampling typically was not frequent enough to identify trends in groundwater caused by short-term (e.g. seasonal) fluctuations in recharge waters, if indeed such trends existed in groundwater. A possible exception is well YLWD-11 during the 1990s, where groundwater sampling and analysis was quite frequent and TIN concentrations at the well mimicked TIN concentrations in the SAR at below Prado with little or no time lag.

· Long-term TIN trends that correspond to long-term TIN trends in SAR water are difficult to identify (with the exception YLWD-11). This is likely due to insufficient frequency of groundwater sampling at wells and/or mixing of groundwaters of differing sources and ages (discussed below).

· In general, TIN concentration at wells frequently is less than TIN moving averages in SAR water at below Prado (Figures 6-14b, for example). This indicates an apparent nitrogen loss from the SAR at below Prado to the well.

· Mixing of groundwaters of different ages and of different sources (CRW recharged at Anaheim Lake, percolation of returns from use and local runoff, etc.), both within the aquifer and within the well column, influences the TIN time histories at wells. This mixing phenomenon, even for wells located adjacent to SAR recharge facilities, is documented by OCWD-sponsored groundwater investigations in the forebay area (Clemens-Knott et al., 1998; Davisson et al., 1999). 6.4 Conclusions

Our scope of work included efforts to correlate the TDS and TIN time histories in the SAR at below Prado to comparable time histories at wells and to the spatial distribution of TIN and TDS at wells. Time history plots and maps were developed in this effort. Our goal was to identify correlations if they existed and to suggest new metrics that would be equally protective of the Orange County groundwater basin and encourage more upstream reclamation. The data available for our analysis was not sufficient to develop useful correlations and suggest new metrics. No new metrics have been proposed.

The observed TDS concentrations at wells that are under recent influence of SAR recharge are frequently higher than the TDS in the SAR suggesting the influence of other sources of recharge including returns from use (easily exceeding 1,000 mg/L) and CRA water (532 to 815 mg/L). The observed TIN concentrations at the same wells are frequently lower than the TIN concentrations in the SAR suggesting the influence of other sources of recharge and nitrogen loss.

The presence of other sources of recharge and the variability in their magnitude (climatic and anthropogenic) greatly complicate the development of a metric based on data at below Prado alone. For example, the source water TDS concentration for potable and non-potable uses in the Orange County basin strongly influences the TDS levels in returns from use. The continued use of CRA water with a TDS almost always greater than 585 mg/L for basin replenishment may require the lowering of the below Prado metric in order to protect beneficial uses in the basin. Recall from Figure 6-4 and Table 6-1 that the use of CRA water for replenishment purposes was significantly greater than SAR water recharge for the historical period used to compute the proposed objective of 585 mg/L; and significantly less than the recharge of SAR water during the current period where ambient TDS concentration was estimated to be 564 mg/L. The predominant use of CRA water for replenishment during the historical period may have created the appearance of assimilative capacity in the current period.

The existing metrics for Reaches 2 and 3 were designed to protect the Santa Ana Forebay subbasin, which has an objective of 600 mg/L. Figure 6-15 is a plot of these metrics for the period 1975 through 1999. The August-only metric is available starting 1983. With the exception of two years (1983 and 1993), the

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August-only TDS metric is always below the Reach 3 objective of 700 mg/L; and the five-year moving average TDS metric for Reach 2 is less than the objective of 650 mg/L since 1978. These same metrics and reach objectives seem to have protected the Orange County management zone as delineated in Phase 2A effort with a proposed objective of 585 mg/L. Basin management changes in the Orange County management zone in the current period, including the use of lower TDS supplies for replenishment, and wetter climatic conditions have also contributed to the appearance of assimilative capacity.

It would take 20 or more years to collect data that could be used to develop a new metric that would be equally protective of the Orange County management zone and encourage more upstream reclamation. Hypotheses, procedures to evaluate/test hypotheses, and supporting studies would be required to design and implement a monitoring program to meet new metric goals. The monitoring period would be long – greater than 20 years. New metrics would be developed after the data is collected and analyzed. Changes in basin management activities in the Orange County management zone during the monitoring period could reduce the utility (invalidate) of the data. The only way to develop a new metric that meets the goal stated above in the next few years will be to conduct modeling studies ranging from the salt flux methods (as discussed by the Task Force) to comprehensive flow and transport modeling.

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7. NITROGEN LOSS COEFFICIENT

The technical memorandum for Task 1, Nitrogen Losses from Recycled Water Systems, was submitted as a draft in October 1998 and as a draft final in November 1998 (WE, Inc., 1998a and 1998b). This section effectively finalizes the technical memorandum for Task 1, with the following additional analyses. Change Order 3 to the contract is an additional scope item in Task 2 to assess historical nitrogen losses from losing reaches of the Santa Ana River.

The original scope of Task 1 was to look at nitrogen transformations/losses beneath four ponds/recharge facilities. The Task Force raised the question about nitrogen losses in the Santa Ana River. WE, Inc. related anecdotal observations that wastewater treatment plants (WWTPs) have discharged nitrogen at greater than 20 milligrams per liter (mg/L) for decades and there has never been a nitrogen problem in groundwater wells influenced by the river, i.e., losing reaches. WE, Inc. also provided a semi-quantitative assessment as part of Task 1 for the reach of the Santa Ana River between the San Jacinto Fault and La Loma Hills. For the purposes of this study, this reach will be called La Loma Hills Reach.

7.1 Objective

The objective of the additional scope item in Task 2 is to assess historical nitrogen losses from other losing reaches of the Santa Ana River, i.e., extend the analyses begun in Task 1 to show it is valid for other reaches of the river and not just unique to the studied reach.

7.2 Definitions

The following definitions are applicable for all phases of the TIN/TDS study:

· Surface Water Translator – Process for quantifying expected transformation of TIN

· Nitrogen Loss Coefficient – Apparent fraction of TIN transformed in system

· TIN Limitation – Concentration of TIN in system effluent to attain water quality objective, at the point of recharge, given nitrogen loss coefficient The TIN Limitation is based only on the nitrogen loss coefficient associated with a given facility. Additional losses and transformations will occur as water moves downstream.

7.3 Procedure

The procedure outlined in Change Order 3 is as follows:

· Define losing reaches of the Santa Ana River

· Compare historical water elevations with ground elevations for near-river wells.

· Develop water elevation contour maps

· Anecdotal information

· Estimate wells that are influenced by the Santa Ana River

· Iterative process losing-reach analysis

· Analyze historical water chemistry.

· Buffer distance from centerline of the Santa Ana River

· Define discharges to the river

· WWTPs

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· Other (Hole Lake, Evans Lake, etc.)

· Estimate N contribution from discharges

· Review historical N and TDS data from WWTPs

· Estimate contributions from other discharge points

· Attempt to account for nonpoint source N contributions

· Develop time-histories of nitrogen at the wells

· Time histories of N in each well influenced by the Santa Ana River in losing reaches.

· ADFM curve

· Water levels 7.4 Nitrogen Losses in the Santa Ana River

7.4.1 Losing Reaches and Orange County Forebay

The losing reaches of the Santa Ana River were estimated by comparing groundwater levels with ground surface elevations. There are two primary reaches that recharge groundwater downstream of the San Jacinto Fault and upstream of Prado Dam: (i) La Loma Hills Reach; and (ii) the reach below Riverside Narrows and upstream of Prado Dam. Figures 3-10 and 3-11 are groundwater elevation contour maps for the Chino, Rialto-Colton, and Riverside Basins for Fall 1973 and Fall 1997, respectively. Figures 3-18 and 3-19 are groundwater elevation contour maps for the Orange County Basins for Fall 1973 and Fall 1997, respectively. These two figures also show the OCWD-Santa Ana River (SAR) recharge facilities and the approximate boundary between the Forebay and the Pressure Zone. Note that there appears to be a groundwater mound downgradient of the OCWD-SAR facilities in the 1973 map. A similar mound is observed downgradient of the Santiago Basins in 1997.

ArcView was used to create a one-mile buffer around the centerline of the Santa Ana River in the losing reaches in the Upper Basin (Figure 7-1). In addition to comparing water level and groundwater level information, the Rapid Assessment Model (RAM) was used to determine wells that are potentially under the influence of the Santa Ana River in Chino Basin. The RAM Tool was developed for the Chino Basin Watermaster. The RAM Tool is currently used in assessing the impacts of projects – recharge basins, desalter well fields, et cetera – on flow patterns in Chino Basin. The RAM Tool utilizes the USGS MODFLOW model. Figure 7-2 shows flow vectors for a 1987 simulation using the RAM tool. The vectors indicate the groundwater flow direction and are proportional to the flow velocity. Figure 7-3 offers corroborating evidence that this reach just north of the La Sierra Hills is a losing reach. (For the purposes of this study, this reach will be called La Sierra Hills Reach.)

In the Orange County Forebay, ArcView was again used to create a one-mile buffer around the centerline of the Santa Ana River. The buffer zone was increased to include a one-mile radius around the OCWD- SAR recharge facilities and to follow the 1973 groundwater mound downgradient of the recharge facilities into the Pressure Zone.

General water chemistry was not conclusive in the losing reach analyses.

7.4.2 Nitrogen in the Santa Ana River and in Wells Under the Influence of the Santa Ana River

Nitrogen loss analyses were conducted previously in La Loma Hills Reach (WE, Inc., 1998b). There are a number of wells along the river in this reach that may have had a significant contribution from the City of San Bernardino WWTP’s discharge upstream of the San Jacinto Fault.

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Historical TIN values averaged 22 mg/L and ranged from 10 to 31 mg/L. TIN values prior to 1976 were estimated to be 23 mg/L (JMM, 1989a). Time histories of nitrate concentrations, groundwater elevations, and ADFM precipitation were plotted (WE, Inc. 1998b). Two observations are apparent in these data:

· While the average TIN concentration in the discharge historically averaged 23 mg/L, nitrate concentrations in the wells in this reach of the Santa Ana River are typically below 10 mg/L.

· Nitrate concentrations tend to increase as water levels decrease. These observations may be a result of the following:

· The ammonium content of the discharge from the WWTP was variable over the period of the analyses, and ammonium may be sorbed to the silt and clay fraction of the river sediments.

· The observed nitrate concentrations in well samples are influenced by well construction, water levels, and local pumping patterns. Nitrate from the WWTP moves as a dissolved component of groundwater near the water table. There would be little vertical dispersion, and the only significant vertical migration of nitrate would be caused by pumping. As water levels decrease, a greater percentage of the groundwater pumped would be discharge from the WWTP.

· Denitrification reactions could be occurring, resulting in the loss of nitrogen from the system. Although, the mechanism(s) are not known, it is important to note that all of the wells potentially impacted by historical discharge from the WWTP have had nitrate concentrations significantly below 10 mg/L. Apparent nitrogen loss coefficients combine losses of nitrogen from the system with ammonium sorption reactions and uptake by plants that may ultimately return nitrogen to the system.

Based on the previous analyses, a similar operational or “black-box” approach was used for assessing nitrogen losses and determining apparent nitrogen loss coefficients in La Sierra Hills Reach and the Orange County Forebay. Time histories of nitrate concentrations with ADFM curves for all the wells depicted in Figures 7-1 and 7-3 were developed and are included in Appendix A. The time histories for the wells in La Sierra Reach also include time histories of nitrate concentrations in the Santa Ana River at the Metropolitan Water District of Southern California (MWD) Crossing. The time histories for the wells in the Orange County Forebay also include time histories of nitrate concentrations in the Santa Ana River at Prado Dam. These time histories were reviewed extensively, and the following observations can be made:

· With relatively few exceptions, nitrate in groundwater samples collected from wells influenced by the Santa Ana River was significantly lower than nitrate concentrations at the respective upstream control point (either MWD Crossing or at Prado Dam).

· Nitrate in groundwater could not be consistently correlated with climatic trends (ADFM) or with fluctuations of concentrations of nitrate in the Santa Ana River.

· Nitrate concentrations decreased by approximately 25 to 75 percent. Figure 7-4 depicts the average nitrate concentration in groundwater for the historical period (1954 to 1973) in the vicinity of La Sierra Hills Reach. Average concentrations in the wells under the influence of the river are typically below 8 mg/L. Figures 7-5 through 7-7 show the average nitrate concentration in groundwater for the historical period in the same reach along with land use for 1949, 1954, and 1963, respectively. Note the increase in dairy and feedlot operations over time.

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Figure 7-8 depicts the average nitrate concentration in groundwater for the current period (1978 to 1997). Average concentrations in the wells under the influence of the river have increased and can exceed 10 mg/L. However, there is considerable evidence that this is a result of land use (dairy and feed lot operations) rather than the river. Indeed, the concentrations in many of these wells far exceed the concentrations in the river, clearly indicating that the river is not the source of high nitrate groundwater. Stable isotope analyses of nitrogen in groundwater collected from wells in this area suggest strongly that the nitrogen in the southern portion of Chino Basin is of animal waste origin (WE, Inc. 1999). Figures 7-9 through 7-11 show the average nitrate concentration in groundwater for the historical period in the same reach along with land use for 1975, 1984, and 1993, respectively.

Figure 7-12 depicts the average nitrate concentration in groundwater for the historical period (1954 to 1973) in the Orange County Forebay. Average concentrations in the wells under the influence of the river and the OCWD-SAR recharge facilities are typically below 5 mg/L. Figure 7-13 depicts the average nitrate concentration in groundwater for the current period (1978 to 1997). Figure 7-14 shows the average nitrate concentration in groundwater for the historical period along with 1957 land use. Note that much of the Forebay area was in irrigated agriculture, historically. Again, the individual well time histories show that there is a significant reduction in nitrate concentrations from Prado Dam to the wells in the Orange County Forebay (Appendix A).

7.5 Updated Data for RIX

Influent and effluent water quality data were only available through March 1998 during the initial study (WE, Inc. 1998a and 1998b). More recent data (April 1998 through November 1999) were processed and analyzed in exactly the same fashion as in the previous study. TIN concentrations of the influent and the effluent are provided in Figures 7-15 (monthly averages) and 7-16 (annual moving averages). The 25 percent nitrogen loss in March 1998 had become a 50 percent loss (from 16 mg/L to less than 8 mg/L) by the fall of 1999. Most of this additional loss is likely due to operational changes at the WWTP (less nitrification).

7.6 Nitrogen Loss Coefficients

Based on additional work performed as part of Change Order 3, the initial recommended nitrogen loss coefficients have been updated. Table 7-1 summarizes the literature review conducted and provides ranges of nitrogen loss reported in the literature and expected ranges if the systems were operated to optimize nitrogen loss. Table 7-2 gives the ranges of apparent nitrogen loss observed in the Santa Ana Watershed:

· Constructed wetlands (Hidden Valley Wetlands Enhancement Project). 50 to 90 percent apparent nitrogen loss. Fifty percent loss was achieved in the water column. Based on the lysimeter and groundwater well data, about 90 percent loss is expected from the influent water to groundwater at the downgradient edge of the site. This can be confirmed with further characterization of the groundwater and influent water (e.g., tracer tests). See further recommendations in the Task 1 Technical Memorandum.

· Recharge basins (Anaheim Lake). No apparent losses to the wells that were studied, Anaheim production well A-27 and monitoring well AMD-9/1. This finding contradicts expected losses from literature review and is not corroborated by other wells near the recharge basins. Not enough data exists to make a definitive recommendation on nitrogen loss from recharge basins.

· RIX. 25 to 75 percent apparent nitrogen loss, depending on operations.

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 7 – NITROGEN LOSS COEFFICIENT

· River Discharge (Losing Reaches of the Santa Ana River and the Orange County Forebay). 25 to 75 percent apparent nitrogen loss. Table 7-2 also provides examples of proposed TIN Limitations based on hypothetical TIN objectives. Note that the upper end of the range is extrapolated and may be out of the linear range.

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 8 – REFERENCES

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 8 – REFERENCES

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TIN/TDS STUDY PHASE 2A FINAL TECHNICAL MEMORANDUM SECTION 8 – REFERENCES

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