The California Water System

California’s economy and culture have always been shaped by the abundance or scarcity of water.

The Golden State’s economy, agricultural production, and population have grown to number one in the nation, largely in pace with the development of its water resources.  

California receives 75 percent of its rain and snow in the watersheds north of Sacramento. However, 80 percent of California’s water demand comes from the southern 2/3 of the state.

As people flocked to the mild climate and agricultural richness of southern California in the late 1800s and early 1900s, it was quickly apparent that the region’s water supply wouldn’t support the swelling population. Several water projects were built to import the precious resource to Southern California and the Central Valley.

Central Valley Project

In the 1930s, the federal government got involved, building the Central Valley Project (CVP) to support the arid but fertile Central Valley and its agricultural economy. Built by the U.S. Bureau of Reclamation, the CVP transports water from Lake Shasta in the north to Bakersfield in the southern San Joaquin Valley.

State Water Project

California’s State Water Project (SWP) was constructed in the 1960s and 1970s to supply water to more than 27 million people and 750,000 acres of farmland. Planned, constructed,and operated by DWR, it is one of the world’s most extensive systems of dams, reservoirs, power plants, pumping plants and aqueducts and remains key to California’s economy. The Edmonston Pumping Plant, south of the Tehachapi Mountains, pumps water 1,926 feet up and over the ridge into Southern California, making it the world’s tallest water lift.

Colorado River

The Colorado Aqueduct, built in the 1930s, transports water from the Colorado River to Southern California. It's operated by the Metropolitan Water District of Southern California (MWD) and is the region’s primary source of drinking water.

Features & Considerations

The Delta

At the heart of California’s water system is the Sacramento-San Joaquin Delta. It's a natural feature of California’s hydrology, where the state’s two mighty rivers join and find their way to sea. It is also the export pool of the SWP, pumping water to millions of people in the San Francisco Bay Area, San Joaquin Valley, Central Coast, and Southern California.


In addition to supplying water to farms, cities, and industry, the SWP provides flood control, recreational opportunities, and water for fish and wildlife. The SWP’s water storage facilities provide year-round recreation opportunities for communities and tourists. Lake Oroville, the SWP’s largest reservoir, was originally built in response to the Yuba City flood of 1955. It serves a critical function to prevent catastrophic flood damage in exceptionally rainy years.


California’s heavily engineered water system is blamed by many for declining fish populations, yet simultaneously praised by others for timely releases of cool water to sustain salmon, steelhead and other species. CVP and SWP pumps in the Delta operate under State and federal guidelines to reduce their effects on sensitive fish species. California continues to modernize its water system to increase water supply reliability while reducing impacts to wildlife and the state’s natural environment.


California has many competing needs for water. Cities, farms, and fish have been pitted against each other for more than a century in a 3-way tug-of-war for a sustainable supply of water. Sustainable groundwater management has been given a high priority as aquifers continue to be over pumped in many areas, particularly during dry periods when surface water to sustain agricultural yields is in short supply.

Infrastructure Investment

In order to maintain a reliable water supply, we must invest in our water system’s infrastructure. Infrastructure includes the aqueduct, canals, dams, spillways, reservoirs, levees, pumping plants, and more. Much of our infrastructure is aging and needs to be bolstered or reconstructed. New infrastructure plans are designed to ensure a reliable and sustainable water supply that supports our economy and our environment.