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Water Resources of Borrego Valley, San Diego County, CA

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Water Resources of Borrego Valley, San Diego County, CA WATER RESOURCES OF BORREGO VALLEY SAN DIEGO COUNTY, CALIFORNIA _____________ A Thesis Presented to the Faculty of San Diego State University _____________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Geological Sciences _____________ by Steven Paul Netto Fall 2001 iii Copyright 2001 by Steven Paul Netto iv ACKNOWLEDGMENTS First and foremost I would like to thank my wife Patti. She has sacrificed much over the years while supporting me in so many ways that I cannot find words adequate to express the gratitude that I feel. She has always been there for me and has carried more than her share as I have been occupied with coursework and this thesis effort, while at many times postponing or altogether foregoing her own interests. To my parents, Arnold and Velma Netto, I owe so many thanks. They have frequently expressed their interest, support and encouragement, and from them I have experienced the deepest kindness and generosity. Inspiring words from my father have stuck with me while finishing this thesis, he reminded me that it would take a lot of tenacity, not just know how, to finally get it done. And to my mother, Joan Fordyce, I also owe a debt of gratitude, for always being there with her love, support and enthusiasm. I am very fortunate to have had the opportunity to work with Dr. David Huntley on this project. It has been an enlightening experience for me and I have learned much from him that I will carry with me throughout the rest of my career. His patient guidance and his willingness to work with me at almost anytime, at his office, over the phone, or even at his own home, have been greatly appreciated. I would also like to thank my committee members, Dr. Kathy Thorbjarnarson and Dr. Christina Tague, for their time and helpful comments during review of this thesis. I would also like to express thanks to Hargis + Associates for all the support they have given me, and all the contributions of company time that they have allowed for the graphics group to work with me on many of the figures in this thesis. Special thanks goes to Mike Palmer and to Chris Ross, for always keeping me motivated and allowing me to keep such a flexible work schedule throughout the past several months. Special thanks also goes to the graphics group, especially Alex Easton and Steve Stewart, for providing their expertise in drafting and valued suggestions with graphics, and to Anita Akacki, for her time spent formatting, reviewing the text, and copying. This thesis would not have been possible without the assistance and cooperation of John Peterson at the County of San Diego, Department of Planning and Land Use, and the many people of Borrego Valley who have contributed so much to this work. Sam and Scott Fortiner and Stan Bauer have allowed access to wells for testing and to their citrus groves for the collection of soil core samples. Andy Gorton at the De Anza Country Club also v allowed access to the golf course for collection of soil core samples. Lin Burzell, with the Borrego Water District, coordinated access to wells that were tested with the assistance of Victor Lugo. Bob Zinser contributed a wealth of information regarding wells, land use and groundwater use in the valley. Jack Laughlin, who was very much concerned with water resource issues in Borrego Valley, was a strong proponent for the forming of a cooperative groundwater management group to evaluate the future water supply for Borrego Valley. Jack Laughlin also provided valuable information for this study regarding groundwater use in the valley. I am lucky to have many friends to thank for their encouragement, help with fieldwork, and shared enthusiasm in my completing this thesis. Steve Blackwell, John Hank, Cathy Martin, Dave Renfrew and John Tyner helped with aquifer testing, soil core sampling, stream gauging, laboratory analysis, and/or drafting. Very special thanks goes to Tom Henderson, who has been both a partner in this study, and a valued friend. vi TABLE OF CONTENTS PAGE ACKNOWLEDGEMENTS ...................................................................................................... iv LIST OF TABLES .................................................................................................................. ix LIST OF FIGURES.................................................................................................................. x CHAPTER I. INTRODUCTION......................................................................................................... 1 Purpose ................................................................................................................. 1 Location and General Features of Borrego Valley ................................................ 1 Topography ..................................................................................................... 4 Climate ............................................................................................................ 4 Vegetation ....................................................................................................... 4 Surface Water Drainages ................................................................................ 9 Land and Water Use........................................................................................ 9 Previous Studies ................................................................................................. 10 II. GEOLOGY ................................................................................................................ 13 Basement Complex ............................................................................................. 13 Imperial Formation .............................................................................................. 15 Canebrake Conglomerate ................................................................................... 15 Palm Spring Formation........................................................................................ 16 Older Alluvium ..................................................................................................... 16 Lacustrine Deposits............................................................................................. 16 Younger Alluvium ................................................................................................ 17 Additional Geologic Units in the Vicinity of Borrego Valley.................................. 17 Borrego Formation......................................................................................... 17 Ocotillo Conglomerate ................................................................................... 17 Structural Features.............................................................................................. 18 Faults............................................................................................................. 18 Folds.............................................................................................................. 18 III. HYDROGEOLOGY ................................................................................................... 21 Definition of Hydrostratigraphic Units .................................................................. 21 Evaluation of Hydraulic Properties ...................................................................... 37 vii CHAPTER PAGE III. (continued) Bauer Wells 1 and 2 ...................................................................................... 39 Borrego Springs Water Company Well 5....................................................... 43 Borrego Water District Well 1 ........................................................................ 48 Borrego Water District Well 8 ........................................................................ 51 Hydraulic Testing Summary .......................................................................... 53 Groundwater Flow and Water Levels .................................................................. 54 IV. WATER BUDGET ..................................................................................................... 61 Sources of Recharge........................................................................................... 61 Precipitation................................................................................................... 64 Double-Mass Precipitation Analysis ........................................................ 65 Precipitation Over the Watershed............................................................ 67 Precipitation Summary............................................................................. 72 Stream Recharge .......................................................................................... 72 Gauged Streams...................................................................................... 75 Ungauged Streams.................................................................................. 85 Bedrock Recharge......................................................................................... 92 Summary of Groundwater Recharge........................................................... 103 Irrigation Return Flow .................................................................................. 103 Sources of Discharge ........................................................................................ 109 Agricultural Water Use................................................................................. 113 Grape Irrigation.....................................................................................
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