August 2025 Probable Minimum 24-Month Study

U.S. Bureau of Reclamation (USBR) | August 15th, 2025

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DR

In addition to the August 2025 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Upper Basin Drought Response Operations Agreement (DROA), Reclamation has conducted additional model runs in August to determine a possible range of reservoir elevations. Probable minimum and probable maximum model runs are conducted in January, April, August, and October, or when necessary to incorporate changing conditions. The Probable Minimum inflow scenario reflects a dry hydrologic condition which statistically would be exceeded 90% of the time. The Most Probable inflow scenario reflects a median hydrologic condition which statistically would be exceeded 50% of the time. The Probable Maximum inflow scenario reflects a wet hydrologic condition which statistically would be exceeded 10% of the time. There is approximately an 80% probability that a future elevation will fall inside the range of the minimum and maximum inflow scenarios. Additionally, there are possible inflow scenarios that would result in reservoir elevations falling outside the ranges indicated in these reports. Related scenarios: August 2025 Most Probable 24-Month Study August 2025 Probable Maximum 24-Month Study  

Base of fresh ground water (approximately 3,000 micromhos) in the San Joaquin Valley, California

U.S. Geological Survey (USGS) | June 30th, 1971

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdr

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdrawal of groundwater, water levels have declined rapidly beneath extensive areas of the valley. Consequently, it becomes necessary to delineate the base of fresh groundwater so that changes in thickness of the fresh-water zone can be monitored, and limited depths of water wells can be determined. In turn, those data will be useful in determining favorable areas for groundwater storage, and areas and depths for waste-water disposal wells. Because other agencies and the U.S. Geological Survey have collected a vast amount of well log and other data, most of the information in this report was assembled from existing files. However, for areas where data were scanty, a few hundred additional electrical logs were collected to supplement the available information.

Beneath the Surface: Why Reservoirs Won't Solve California's Water Woes

Center for Biological Diversity (CBD) | November 19th, 2024

Water storage and conveyance have fundamentally shaped modern California. The vast agricultural industry, as well as globally important cities like Los Angeles, were made

Water storage and conveyance have fundamentally shaped modern California. The vast agricultural industry, as well as globally important cities like Los Angeles, were made possible by storing and moving water around the state. Reservoirs are one of the primary components of California’s water storage system. There are nearly 1,500 surface storage reservoirs throughout the state, which together can store a year’s supply of water for farms and cities. But reservoirs come with high costs. They destroy and degrade habitats and alter flows in rivers and streams, harming native fish and wildlife. They emit significant amounts of greenhouse gases, worsening climate change. They cost taxpayers billions of dollars to build and maintain. And as the climate continues to warm, reservoirs will become less efficient, losing more and more of the water they hold to evaporation.  This report examines reservoirs’ environmental harms and explains why new reservoirs are not the solution to our 21st century water problems. 

Bulletin 118 - California's Groundwater Update 2013

California Department of Water Resources (DWR) | April 15th, 2015

California’s Groundwater Update 2013 compiles and analyzes readily available groundwater information to characterize California’s groundwater basins, aquifers, and we

California’s Groundwater Update 2013 compiles and analyzes readily available groundwater information to characterize California’s groundwater basins, aquifers, and well infrastructure. It also presents data and analysis related to groundwater monitoring efforts, aquifer conditions in response to extraction, groundwater management practices, and conjunctive management programs. It expands and enhances baseline groundwater information on a regional scale, identifies challenges associated with sustainable groundwater management, and helps guide implementation of diverse resource management strategies. The set of data, information, and analysis developed can help local and regional groundwater managers, as well as individual well owners, better understand California’s hidden and commonly misunderstood resource. This Bulletin has been uploaded in the following separate files reflecting hydrologic regions and appendices. Chapter One / Introduction  Chapter Two / State-wide Update  Chapter Three / North Coast Chapter Four / San Francisco Bay Chapter Five / Central Coast Chapter Six / South Coast  Chapter Seven / Sacramento River Chapter Eight / San Joaquin River Chapter Nine / Tulare Lake Chapter Ten / North Lahontan Chapter Eleven / South Lahontan Chapter Twelve / Colorado River Appendix A: Methods and Assumptions Appendix B: CASGEM Basin Prioritization Appendix C: Groundwater Use Data 2010-2015 Appendix D: Conjunctive Management Survey Appendix E: Change in Groundwater in Storage Appendix F: Subsidence

Bulletin 132-00 Management of the California State Water Project

California Department of Water Resources (DWR) | December 3rd, 2001

Bulletin 132-01 Management of the California State Water Project

California Department of Water Resources (DWR) | December 1st, 2002

Bulletin 132-02 Management of the California State Water Project

California Department of Water Resources (DWR) | January 5th, 2004

Bulletin 132-03 Management of the California State Water Project

California Department of Water Resources (DWR) | December 1st, 2004

Bulletin 132-04 Management of the California State Water Project

California Department of Water Resources (DWR) | September 30th, 2005

Bulletin 132-05 Management of the California State Water Project

California Department of Water Resources (DWR) | December 1st, 2006