California Water Use

Science Center Objects

The U.S. Geological Survey's National Water-Use Information Program compiles the nation's water-use data at the county, state, and national levels. USGS five-year reports on national and state water-use estimates between 1950-2015 are posted on the web at: USGS water-use data for states and counties for 1985-2015 are available at:

As part of the USGS National Water Use Compilation, the California Water Science Center works in cooperation with local, State, and Federal agencies as well as academic and private organizations to collect and report total water withdrawals for California.

Water-use estimates are compiled by withdrawal source type, use category, and county.

  • Withdrawal source types include groundwater, both fresh and saline,
  • and surface water, both fresh and saline;
  • Eight water-use categories include thermoelectric, public, domestic, livestock, mining, industrial, irrigation, and aquaculture.

For California, population data used to estimate public water-supply use comes from Urban Water Management Plans, California Department of Water Resources, California Department of Public Health, and U.S. Environmental Protection Agency data. Population data used to estimate domestic, self-supplied water use came from the difference between the Census population and the public-supply population.

water use facts on a water bubble background

Did you know these fun facts about California water use?  Irrigation is the water withdrawal category that uses the most water every year.  California's total water use has been decliing since 1980. California uses more water than any other state. (Public domain.)


The terms and units used in this report are similar to those used in previous USGS National Water-Use Reports and are defined in the Glossary. Water-use data are expressed in units of gallons per day.

Withdrawal estimates for each category represent the total amount of water removed from the water source, regardless of how much of that total is consumptively used. In most cases, some fraction of the total withdrawal will be returned to the same or a different water source after use and is available for other withdrawals.

Limitations of Water-Use Data

The California water-use summary presented here is based on estimates compiled from a variety of sources. There is significant uncertainty associated with many of these estimates.

Withdrawals for crop irrigation are among the least accurate of the estimates because withdrawals are generally not measured directly, and must be calculated based on crop acreage, crop coefficients, stage ratios, irrigation-system efficiency, and precipitation. Data on withdrawals for public supply are more accurate because those estimates are based primarily on site-specific information. Powerplant water use and mining information are considered the most accurate data.

Sources of California Water Use Data and Methods of Analysis

The USGS California Water Science Center publishes water information on many topics, including water use. USGS national guidelines for preparing water-use estimates were followed. Water-use estimates and ancillary data were entered into a State aggregate water-use database and reviewed within the USGS and by cooperating agencies.

The following national data are available to each State: U.S. Environmental Protection Agency (USEPA) Safe Drinking Water Information System (SDWIS); U.S. Census Bureau, population; U.S. Department of Agriculture (USDA) Farm and Ranch Irrigation Survey; USDA Census of Agriculture; USDA, national agricultural statistics; and U.S. Department of Energy-Energy Information Administration (USDOE-EIA), steam-electric plant statistics.

The USGS California Water Science Center is responsible for determining the most reliable sources of data, compiling and analyzing those data, determining its comprehensiveness, and estimating missing data where appropriate, and preparing documentation of the sources and methods used to estimate water use for California. California and other states have published reports on water use as part of the National Water Use Information Program.




The authors gratefully acknowledge the assistance provided by the many State and local agencies that shared data and expertise with the USGS. Cooperators include State agencies that manage water resources, operate data-collection programs, and administer regulations on water use and natural resources.


The recommended citation for this web page is:
Water Use in California, 2014, Brandt, Justin; Sneed, Michelle; Rogers, Laurel Lynn; Metzger, Loren F.; Diane Rewis; House, Sally
USGS Data Website, doi:10.5066/F7KD1VXV