San Diego County’s Water Sources

Local surface water runoff from rainfall is an important part of the San Diego region’s water supply, but it hasn’t provided enough water to meet all of the region’s needs since 1947.

 
Sources of San Diego County’s Water Supply
(2009-2013 five-year average)


San Diego County’s water supplies are imported from sources hundreds of miles away. These imported sources are:

Colorado River, Credit: Alan Stark
Lower Colorado River

Colorado River

More than 50 percent of the region’s water comes from the Colorado River. The Water Authority purchases some Colorado River supplies from the Metropolitan Water District of Southern California (MWD). The Water Authority also obtains its own Colorado River water supplies through a long-term water conservation and transfer agreement with the Imperial Irrigation District and two canal-lining agreements that transfer conserved water to San Diego County. These supplies are transported to San Diego County through MWD’s water distribution facilities.

 


 


The Bay-Delta

Bay-Delta

Typically in recent years about 30 percent of the region’s water has come from the Bay-Delta in Northern California. The Bay-Delta is a vast network of channels and islands at the convergence of the Sacramento and San Joaquin rivers, which collect runoff from the Sierra Nevada. The State Water Project, operated by California’s Department of Water Resources, collects water from the Bay-Delta and pumps it south to customers including MWD. The Water Authority then purchases some of this supply from MWD.

 

Local Supplies

Local supplies, including surface water, groundwater, recycled water and conservation, currently meet about 20 percent of the region’s water demand.

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