In 1960, California voters approved financing for construction of
the initial features of the State Water Project (SWP). The
project includes some 22 dams and reservoirs, a Delta pumping
plant, a 444-mile-long aqueduct that carries water from the Delta
through the San Joaquin Valley to southern California. The
project begins at Oroville Dam on the Feather River and ends at
Lake Perris near Riverside. At the Tehachapi Mountains, giant
pumps lift the water from the California Aqueduct some 2,000 feet
over the mountains and into southern California.
A number of large population centers in California have developed
their own extensive water projects. The Hetch Hetchy Project
transports Tuolumne River water 156 miles from the Central Sierra
to San Francisco and peninsula cities.
The East Bay Municipal Utility District supplies cities on the
east side of San Francisco Bay with Mokelumne River water.
About 30 percent of California’s total annual water supply comes
from groundwater in normal years, and up to 60 percent in drought
years. Local communities’ usage may be different; many areas rely
exclusively on groundwater while others use only surface water
supplies. Contrary to popular opinion, groundwater does not exist
in underground lakes. Groundwater fills pores (spaces) between
sand, gravel, silt and clay in water-bearing formations known as