Sacramento River

California's Fourth Climate Change Assessment Statewide Summary Report

Governor's Office of Planning and Research (OPR) | August 27th, 2018

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors. This cutting-edge research initiative is comprised of a wide-ranging body of technical reports, including rigorous, comprehensive climate change scenarios at a scale suitable for illuminating regional vulnerabilities and localized adaptation strategies in California; datasets and tools that improve integration of observed and projected knowledge about climate change into decision- making; and recommendations and information to directly inform vulnerability assessments and adaptation strategies for California’s energy sector, water resources and management, oceans and coasts, forests, wildfires, agriculture, biodiversity and habitat, and public health. In addition, these technical reports have been distilled into summary reports and a brochure, allowing the public and decision-makers to easily access relevant findings from the Fourth Assessment. Click here for key findings brochure

California's Groundwater Conditions Semi-Annual Update: March 2023

California Department of Water Resources (DWR) | March 15th, 2023

These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). This report uses groundwater data received electr

These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). This report uses groundwater data received electronically by DWR as of February 15, 2022, through the conclusion of Water Year 2022, and the start of Water Year 2023.

California's Groundwater Conditions: Semi Annual Update May 2024, Spring Bulletin 118

California Department of Water Resources (DWR) | May 6th, 2024

In WY 2023, increased surface water supply led to a significant reduction in statewide groundwater extraction, amounting to a total annual extraction of 9.5 million acre-

In WY 2023, increased surface water supply led to a significant reduction in statewide groundwater extraction, amounting to a total annual extraction of 9.5 million acre-feet, a stark contrast to the 17 million acre-feet extracted in WY 2022.

California's Groundwater Conditions: Semi-Annual Update May 2025

California Department of Water Resources (DWR) | June 24th, 2025

This semi-annual report presents data received by DWR as of April 2025 and reflects the impacts of a few wet years after a drought period. However, it should be noted tha

This semi-annual report presents data received by DWR as of April 2025 and reflects the impacts of a few wet years after a drought period. However, it should be noted that groundwater response is a slow process and may take months to years to fully respond to changes in surface water conditions. This report is the latest in a series of Semi-Annual Groundwater Conditions Updates, last published in October 2024. These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). The most recent groundwater data is available on the California’s Groundwater Live website, which is updated daily as data is received by DWR. Additional data and information are available in the CNRA Open Data and Water Data Library websites.

California's Groundwater Update 2025 (Bulletin 118)

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

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) is a compendium of statewide data and information on the occurrence, nature, use, and conditi

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) is a compendium of statewide data and information on the occurrence, nature, use, and conditions of California’s groundwater resources and management. Chapters 1-6 Chapter 7 Appendix A: Findings and Recommendations Appendix B: Glossary Appendix D: Citations, Reference Materials, and Links Appendix I: Land Subsidence  

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.