State Water Project 

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The California State Water Project (SWP) is a water storage and delivery system of reservoirs, aqueducts, power plants and pumping plants extending more than 700 miles—two-thirds the length of California.

Planned, constructed, and operated by the Department of Water Resources, the SWP is the nation’s largest state-built, multi-purpose, user-financed water project. It supplies water to more than 26 million people in northern California, the Bay Area, the San Joaquin Valley, the Central Coast and southern California. SWP water also irrigates about 750,000 acres of farmland, mainly in the San Joaquin Valley.

The primary purpose of the SWP is water supply. SWP was designed to deliver nearly 4.2 million acre-feet of water per year. Water is received by 29 long-term SWP Water Supply Contractors who distribute it to farms, homes, and industry. Water supply depends on rainfall, snowpack, runoff, water in storage facilities, and pumping capacity from the Delta, as well as operational constraints for fish and wildlife protection, water quality, and environmental and legal restrictions.


The SWP was designed to provide many additional benefits:

  • Flood control – The flood of 1955, which submerged Yuba City, was the impetus for the construction of Lake Oroville.
  • Power generation – The SWP produces hydroelectric power to operate pumping facilities required to move water from Northern to Southern California. The SWP sells power when it generates a surplus of electricity.
  • Recreation – SWP lakes and reservoirs provide opportunities to swim, picnic, waterski, boat, fish, hike, bike, camp, and horseback ride. Visitors are also welcome at three visitors centers located at Lake Oroville, San Luis Reservoir, and Lake Pyramid.
  • Fish and wildlife habitat –The SWP is operated to protect fish and wildlife with fish hatcheries, fish screens and passages, mitigation agreements, fish surveys and monitoring, a fish salvage facility, habitat restoration, and restricted pumping schedules.
Environmental Roles

The SWP operates to balance the needs of water delivery and environmental protection.  The sustainability of California’s water resources depends on the environmental health of the Sacramento-San Joaquin Delta. In cooperation with the federal Central Valley Project, we operate the SWP to limit salinity intrusion into the Sacramento-San Joaquin Delta and Suisun Marsh by supplementing freshwater outflows to the ocean and limiting water exports from the Delta during certain times of the year.

We work cooperatively with regulatory agencies to develop interim and long-term operations solutions that are responsive to federal and State endangered species acts. We participate in habitat restoration projects that preserve and protect special status species impacted by SWP operations. We assess, evaluate, and propose solutions to improve system water management performance through improved operational agreements, economic analyses, and other methods.

Climate change presents an additional challenge to SWP operations. We are studying climate change to understand its impacts on water delivery and the environment, to ensure a sustainable water supply.