ENVIRONMENTALSETTING OFTHE SAN JOAQUIN-TULARE BASINS, CALIFORNIA by Jo Ann M. Gronberg, Neil M. Dubrovsky, Charles R. Kratzer, Joseph L. Domagalski, Larry R. Brown, and Karen R. Burow U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 97-4205 National Water-Quality Assessment Program r- o CD Sacramento, California 1998 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Branch of Information Services Water Resources Division Box 25286 Placer Hall Denver, CO 80225-0286 6000 J Street Sacramento, CA 95819-6129 FOREWORD The mission of the U.S. Geological Survey Improve understanding of the primary (USGS) is to assess the quantity and quality of the natural and human factors that affect earth resources of the Nation and to provide informa­ water-quality conditions. tion that will assist resource managers and policymak- This information will help support the development ers at Federal, State, and local levels in making sound and evaluation of management, regulatory, and moni­ decisions. Assessment of water-quality conditions and toring decisions by other Federal, State, and local trends is an important part of this overall mission. agencies to protect, use, and enhance water resources. One of the greatest challenges faced by water- resources scientists is acquiring reliable information The goals of the NAWQA Program are being that will guide the use and protection of the Nation's achieved through ongoing and proposed investigations water resources. That challenge is being addressed by of 59 of the Nation's most important river basins and Federal, State, interstate, and local water-resource aquifer systems, which are referred to as study units. agencies and by many academic institutions. These These study units are distributed throughout the organizations are collecting water-quality data for a Nation and cover a diversity of hydrogeologic settings. host of purposes that include: compliance with permits More than two-thirds of the Nation's freshwater use and water-supply standards; development of remedia­ occurs within the 59 study units and more than two- tion plans for specific contamination problems; opera­ thirds of the people served by public water-supply sys­ tional decisions on industrial, wastewater, or water- tems live within their boundaries. supply facilities; and research on factors that affect National synthesis of data analysis, based on water quality. An additional need for water-quality aggregation of comparable information obtained from information is to provide a basis on which regional- the study units, is a major component of the program. and national-level policy decisions can be based. Wise This effort focuses on selected water-quality topics decisions must be based on sound information. As a using nationally consistent information. Comparative society we need to know whether certain types of studies will explain differences and similarities in water-quality problems are isolated or ubiquitous, observed water-quality conditions among study areas whether there are significant differences in conditions and will identify changes and trends and their causes. among regions, whether the conditions are changing The first topics addressed by the national synthesis are over time, and why these conditions change from pesticides, nutrients, volatile organic compounds, and place to place and over time. The information can be aquatic biology. Discussions on these and other water- used to help determine the efficacy of existing water- quality topics will be published in periodic summaries quality policies and to help analysts determine the of the quality of the Nation's ground and surface water need for and likely consequences of new policies. as the information becomes available. To address these needs, the U.S. Congress appropri­ ated funds in 1986 for the USGS to begin a pilot pro­ This report is an element of the comprehensive gram in seven project areas to develop and refine the body of information developed as part of the NAWQA National Water-Quality Assessment (NAWQA) Pro­ Program. The program depends heavily on the advice, gram. In 1991, the USGS began full implementation of cooperation, and information from many Federal, the program. The NAWQA Program builds upon an State, interstate, Tribal, and local agencies and the existing base of water-quality studies of the USGS, as public. The assistance and suggestions of all are well as those of other Federal, State, and local agencies. greatly appreciated. The objectives of the NAWQA Program are to: Describe current water-quality conditions for a large part of the Nation's freshwater streams, rivers, and aquifers. Describe how water quality is changing Robert M. Hirsch over time. Chief Hydrologist CONTENTS Abstract ..................................................................................................................................................................... 1 The National Water-Quality Assessment Program ............................................................................................................... 1 San Joaquin-Tulare Basins ................................................................................................................................................... 3 Location and Physiography ........................................................................................................................................ 3 Geology .................................................................................................................................................................^ 5 Climate..............................................................................._ 6 Natural Hydrology and Native Habitats ..................................................................................................................... 6 Ecology ..............................................................................._ 11 Ecoregions ........................................................................................................................................................ 11 Aquatic Biology ................................................................................................................................................ 11 Surface-Water Hydrology ........................................................................................................................................... 14 Distribution Systems ......................................................................................................................................... 14 Major Reservoirs .............................................................................................................................................. 15 Annual Discharge ............................................................................................................................................. 15 Seasonal Discharge ........................................................................................................................................... 17 Water Storage and Availability ......................................................................................................................... 20 Ground-Water Hydrology ........................................................................................................................................... 23 Regional Ground-Water Flow System .............................................................................................................. 23 Predevelopment Ground-Water-Flow ............................................................................................................... 25 Ground-Water Development and Response ...................................................................................................... 25 Factors Affecting Water Quality ........................................................................................................................................... 27 Land Use ......................................................................... 29 Agricultural Land Use ...................................................................................................................................... 29 Urban Land Use ................................................................................................................................................ 32 Water Use .................................................................................................................................................... 32 Point Sources ............................................................................ 32 Agricultural Sources ................................................................................................................................................... 36 Discharges to the San Joaquin River ................................................................................................................ 36 Pesticides .......................................................................................................................................................... 36 Nutrients from Fertilizers ................................................................................................................................