California's Water System

Most of California's water comes from winter rains and snows and evaporates or is absorbed into trees and vegetation. About 40% flows into rivers and streams or is absorbed into underground layers of rock called aquifers. 

Water taken from the ground can then be used for homes, agriculture, industry or other uses. 

75% of California's water comes from rain and snow that falls north of Sacramento and eventually finds its way into streams and rivers. But over 80% of that water is used by the southern 2/3 of the state. 

California is a very large state that depends on a complex system for distributing water to where it is needed. 

The need for water has always impacted where human beings lived. For thousands of years, Native Americans in California established villages and encampments near water sources like lakes, streams and rivers.

In the 18th century, the Spanish established missions, presidios and pueblos in California. They designed irrigation systems to bring water from long distances to support crops and livestock.

In the 19th century, with statehood and the birth of industries such as mining and timber, officials began planning ways to channel water to support the growing economy and to prevent flooding around cities like Sacramento. 

As the state's population grew in the early 20th century, cities began to expand, as did their need for water. Large-scale agriculture also became an important part of the economy. But much of this growth took place in areas that had little rainfall. Plans were made to bring water from California's wetter regions.

The Central Valley Project is one of the largest water transport systems in the world. It began in 1933 as a way to manage flooding, store water and produce electricity, and eventually grew into a whole series of dams and reservoirs. Water is transported from Lake Shasta in Northern California all the way to Bakersfield (450 miles). There are 18 dams and reservoirs that make up the Central Valley Project. The Central Valley Project stores and delivers about 20% of the state's water.

The State Water Project began in 1960, and carries water from the Feather River in far northern California to the Central Valley, the South Bay Area and Southern California. Much of that water is transported by the 444 mile long California Aqueduct, which travels along 1-5 for many miles.

About 70% of the State Water Project water goes to residential, municipal and industrial use (mostly in Southern California, but also the South Bay Area), while the remaining 30% goes to agriculture in the San Joaquín Valley. The State Water Project includes the world's highest water lift that brings water over the Tehachapi Mountains south of Bakersfield.

In addition to the Central Valley Project and the State Water Project, there are a number of other large water projects, including the Hetch Hetchy Aqueduct that delivers water from the Sierra Nevada to the San Francisco Bay Area, the Los Angeles Aqueduct, which transports water from the the Owens Valley and the Mono Basin to Los Angeles,  the Colorado River, which supplies urban water for much of Southern California as well as irrigation for much of Southern California's agriculture, and the Mokelumne Aqueduct, which delivers water from the Mokelumne River to the eastern Bay Area.

Nearly 2/3 of the water delivered to cities and much of its farm water comes from the Sacramento-San Joaquín Delta. The Delta is where two of the state's largest rivers, the Sacramento and the San Joaquin, converge and eventually flow into the San Francisco Bay.

Much of the water from the Delta is channeled into the Central Valley Project and the State Water Project. The region around the Delta is mostly agricultural, and was the first region in California developed specifically for farming. Each year the Delta produces more than $500,000,000 worth of fruits and vegetables. 

California's water supply now supports 35 million people and more than 5.68 million acres of farmland. And California has more irrigated farmland than any other state.