Bulletin 118: California's Groundwater Update 2020 (draft)

California Department of Water Resources (DWR) | March 1st, 2021

Groundwater is a precious and limited resource that is used in meeting the needs of California’s large and small urban areas, rural groundwater users, irrigated agricul

Groundwater is a precious and limited resource that is used in meeting the needs of California’s large and small urban areas, rural groundwater users, irrigated agriculture, and the environment. Since the last California’s Groundwater (CalGW) Update in 2003, there has been significant changes to land use, water use, water application practices, and water allocations. In addition, the effects of climate change have affected California’s reliance on groundwater. It is expected that there will be additional changes in land use, water use, adjustments in water allocations, and that climate change will continue to affect the environment, thus elevating the importance of the reporting in CalGW Updates.  According to the last comprehensive report, California’s Groundwater Update 2003 (CalGW Update 2003), California’s reliance on groundwater was approximately 30 percent during a wet-to-average precipitation water year and approximately 40 percent during dry periods. Since then, the percentage of groundwater reliance has increased to between 30 and 40 percent during above normal to-wet years and to as much as 58 percent during dry periods (California Department of Water Resources 2018).

Bulletin 16, Report of Sacramento-San Joaquin Water Supervision for 1949

California Department of Water Resources (DWR) | June 1st, 1950

Bulletin 161-2025, 2025 Annual Water Supply and Demand Assessment Summary Report

California Department of Water Resources (DWR) | September 23rd, 2025

This report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports

This report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports) for the State Water Resources Control Board (State Water Board). As directed by the California Water Code (CWC) §10644(c)(1)(B), this summary report includes water shortage information at the supplier level, as well as regional and statewide analyses of water supply conditions. 

Bulletin 39-I, South Coastal Basin Investigation, Records of Ground Water Levels at Wells for the Year 1940, Precipitation Records for the Season 1939-40

California Department of Water Resources (DWR) | July 1st, 1941

Bulletin No. 1 Water Resources of California

California Department of Water Resources (DWR) | June 1st, 1951

Few convictions are more generally or more firmly fixed in the minds of the people of California than that our number one economic problem is to put to best use our inv

Few convictions are more generally or more firmly fixed in the minds of the people of California than that our number one economic problem is to put to best use our invaluable water supply. Previous investigations have shown that this supply is adequate for a population much larger than the present 10,500,000, and that with additional storage and redistribution of water, most of the agricultural lands of the State, except only some desert and higher areas, can be serviced for irrigation as our expanding economy and human requirements justify the costs involved. Furthermore, without too great a sacrifice of reasonable needs, our multiple uses of water for domestic and municipal consumption, for agriculture, industry, power, recreation, and wild life preservation can be so coordinated as to achieve maximum benefits for the largest number of people. This bulletin presents the first results of new studies, under direction of the State Water Resources Board, aimed at a solution of this number one problem. It brings together in one volume the principal basic data regarding water in California that have been accumulated up to 1947, thereby becoming an inventory of the water resources of the State. Concurrently with preparafion of this inventory, work has progressed on the other principal phases of the program: determination of present use of water and of ultimate water requirement, and formulation of "The California yvater Plan" to meet that requirement.

Bulletin No. 10 Placer County Investigation

California State Water Resources Control Board (SWRCB) | June 30th, 1955

Bulletin No. 104 Planned Utilization of Ground Water Basins: Coastal Plain of Los Angeles County

California Department of Water Resources (DWR) | August 26th, 1968

Bulletin No. 11 Ground Water Resources of Southern San Joaquin Valley

State of California | January 1st, 1927

Bulletin No. 11 San Joaquin County Investigation

California State Water Resources Control Board (SWRCB) | June 30th, 1955

Bulletin No. 12, Summary Report on the Water Resources of California and a Coordinated Plan for their Development

State of California | January 1st, 1927