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Water Portfolios
Water Plan Water Balances

The primary reason for using water portfolio tables and flow diagrams is to provide an accounting of all water that enters and leaves the state and how it is used and exchanged between the regions. This is important to all water planning activities. Water portfolio data provide information for comparison about how water uses and sources of supply can vary between the wet, average, and dry hydrologic conditions for each of the hydrologic regions. The statewide information has been compiled from the 10 hydrologic regions.

Water Use in California

California’s water supplies vary from place to place, season to season, and year to year. The state’s water users (environmental, agricultural, and urban sectors) have variable needs for the quantity, quality, timing, and place of use. Update 2013 developed water balances to show water uses and sources of water for the individual water years from 2001 through 2010 (shown in the figure below). This 10-year period included some moderately dry years, from 2007 to 2009, and wet years in 2005 and 2006, and demonstrates the state’s variability with regard to water use and water supply. Some key insights from this information are that urban water uses are more adaptable to supply limitation, and groundwater use increases in drier years when surface supplies decline.

  • Where Does California’s Water Go?
    • California’s water supports three main sectors: cities and communities, agriculture and environment.
    • On average, the proportion of water used by each sector is 10 percent cities and communities, 40 percent agriculture, and 50 percent environment.
    • This statewide ratio varies widely depending upon whether a year is wet or dry. In wet years, the proportion that serves environmental purposes can be 60 percent or more, while in dry years that proportion drops to roughly one-third.
    • Water often serves double duty; water allocated for one purpose is often reused for other purposes downstream.

Click on a year below to see how climate affects water use in California.

Water Year 2006

Water Year 2006 was a wet year. A total of 108 million-acre-feet (MAF) of water was used in the state. Hover over the chart to see the percentage used in each sector.

Water Year 2010

Water Year 2010 was an average year. A total of 80 million-acre-feet (MAF) of water was used in the state. Hover over the chart to see the percentage used in each sector

Water Year 2007

Water Year 2007 was a dry year. A total of 77 million-acre-feet (MAF) of water was used in the state. Hover over the chart to see the percentage used in each sector

Average Water Use 2002-2010

Water use between 2002-2010 was an average of 83 million-acre-feet (MAF) per year. Hover over the chart to see the percentage used in each sector


Water Use by Hydrologic Region

California has a variety of climates and landforms. The amount and variability of precipitation can change dramatically across California, such that statewide average information does not truly depict regional conditions. Each region has unique challenges in meeting agricultural, urban, and environmental water uses from year to year with available supplies. Water use data for each hydrologic region is included in Update 2013 Volume 2, Regional Reports. For detailed groundwater use data, see California's Groundwater Update 2013.


Additional Information

For more detailed information about water portfolios, go to Update 2013 Volume 5, Technical Guide. You can also email your questions to cwpcom@water.ca.gov.