San Joaquin River

California's Rivers and Streams

Public Policy Institute of California (PPIC) | January 26th, 2026

California's Water Supply Strategy: Adapting to a Hotter, Drier Future

California Department of Water Resources (DWR) | August 16th, 2022

California's Water Supply Strategy: Adapting to a Hotter, Drier Future

Office of Governor Gavin Newsom | August 11th, 2022

California's Water–Energy Relationship

California Energy Commission (CEC) | November 1st, 2005

This report examines the dynamic give-and-take relationship between California’s water and energy resources. Among many other issues, this staff report examines the s

This report examines the dynamic give-and-take relationship between California’s water and energy resources. Among many other issues, this staff report examines the state’s water sector and its energy use, along with changes likely to occur in the future.

California’s Agricultural and Urban Water Supply Reliability and the Sacramento–San Joaquin Delta

University of California, Davis (UC Davis) | October 13th, 2016

Much of the water supplied in California for agriculture and cities is taken directly from the Sacramento–San Joaquin Delta (Delta) or indirectly from surface and groun

Much of the water supplied in California for agriculture and cities is taken directly from the Sacramento–San Joaquin Delta (Delta) or indirectly from surface and groundwater diversions upstream. These water supplies have great economic and social value, and considerable ecosystem effects. Long thought of as the major source of water for economic growth in California, the reliability of water supplied from the Delta is threatened by drought, flood, climate change, earthquakes, growing water demands, and deteriorating conditions for endangered species and native ecosystems. Research in recent years has improved understanding of how management of the Delta ties together the quantity and quality of water available statewide. These ties run from the Sierra mountains and coastal streams, through the Central Valley, to the San Francisco Bay Area, and over the Tehachapi Mountains to southern California. For decades, Californians counted on reducing Delta outflows to supply water for growing water demands in its watershed and in water importing areas. With greater competition for water, concern for environmental effects, and a changing climate, the reliability of such supplies is now diminishing. This must lead to tighter accounting and modeling of water supplies in the Delta and throughout its watershed. This paper reviews issues about Delta water supplies, operations, regulations, and reliability; the economic value of supply; costs of unreliability in quantity and quality; and several directions for further scientific and technical work on water supply reliability.

California’s Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California’s Central Valley

U.S. Geological Survey (USGS) | June 16th, 2009

Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley’s population has nearly

Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley’s population has nearly doubled to 3.8 million people. It is expected to increase to 6 million by 2020. Statewide population growth, anticipated reductions in Colorado River water deliveries, drought, and the ecological crisis in the Sacramento–San Joaquin Delta have created an intense demand for water. Tools and information can be used to help manage the Central Valley aquifer system, an important State and national resource. The U.S. Geological Survey (USGS) has released results from a study on the largest water reservoir in the State of California, the Central Valley groundwater system. The findings show continued loss of stored groundwater in the southern part of the valley (see figure below). Since about 1960, groundwater has been depleted by almost 60 million acre-feet, which is, on average, enough to supply every resident of California with water for 8 years. In order to complete the study, the USGS developed an extensive, detailed three-dimensional (3D) computer model of the hydrologic system of the Central Valley (Faunt, 2009). The Central Valley Hydrologic Model (CVHM) simultaneously accounts for changing water supply and demand across the landscape, and simulates surface water and groundwater flow across the entire Central Valley. This new hydrologic modeling tool can be used by water managers to understand how water moves through the aquifer system, predict water-supply scenarios, and address issues related to water competition in California and the Central Valley including: Conjunctive water use (interdependent use of surface water and groundwater); Conservation of agricultural land; Land-use change, including environmental concerns and urbanization, and its effects on water resources; and Effects of climate change.

California’s Future: Water

Public Policy Institute of California (PPIC) | January 31st, 2020

Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional dif

Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional differences in water availability and demand. California’s “water grid”—the network of surface and groundwater storage and conveyance systems that connects most water use in the state—was designed to move water to population and farming centers in the Bay Area, the San Joaquin Valley, and Southern California, while also protecting residents from floods. As the state has changed, its water challenges have intensified. The Sacramento–San Joaquin Delta is an increasingly fragile link in the water grid. California’s extensive network of dams is aging. Agricultural demand is becoming less flexible, as farmers increase tree crops (especially nuts), which must be watered every year. Some poor—mostly rural— communities lack safe drinking water. Conflicts are growing between human water use and water needed for fish and other wildlife. And the latest cycle of droughts and floods highlights the growing threat of climate change. Climate pressures are making it harder to simultaneously store water for droughts, manage flood risk, and protect fresh- water ecosystems. But leaders across the state are addressing the challenges of a more volatile climate, and the Newsom administration is developing a water resilience portfolio to adapt all aspects of water management to the “new normal.”

California’s Groundwater Conditions Semi-Annual Update: October 2022

California Department of Water Resources (DWR) | October 15th, 2022

This report is a semi-annual update of the annual Groundwater Conditions Report published in March 2022 and part of DWR’s California’s Groundwater (Bulletin 118). Wat

This report is a semi-annual update of the annual Groundwater Conditions Report published in March 2022 and part of DWR’s California’s Groundwater (Bulletin 118). Water Year 2022 groundwater data used in this report includes data received electronically by DWR as of August 31, 2022.

California’s Groundwater Conditions: Semi-Annual Update, October 2023, Fall Bulletin 118 Information Update

California Department of Water Resources (DWR) | October 12th, 2023

This semi-annual report presents data received by DWR as of August 31, 2023, and partially reflects the impacts of recent storms, flooding, and natural and managed aquife

This semi-annual report presents data received by DWR as of August 31, 2023, and partially reflects the impacts of recent storms, flooding, and natural and managed aquifer recharge. However, it should be noted that groundwater response is a slow process and takes months to years to fully respond to changes in surface water conditions.

California’s Groundwater: Bulletin 118 — Update 2025 Highlights

California Department of Water Resources (DWR) | October 20th, 2025

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information on the occurrence, nature, uses, management, climate change vulnerability, monitoring, and conditions of California’s groundwater resources. Building on the legacy of Bulletin 118 and past California Water Plans, CalGW Update 2025 synthesizes recent data — available up to December 2023 — and closes key knowledge gaps to inform more effective statewide groundwater planning and decision-making.  CalGW Update 2025 consists of this Highlights document and a detailed statewide report, supported by a series of appendices.