Competition for water resources is growing throughout
California, particularly in the Central Valley. Since 1980, the
Central Valley's population has nearly doubled to 3.8 million
people. It is expected to increase to 6 million by 2020.
Statewide population growth, anticipated reductions in Colorado
River water deliveries, drought, and the ecological crisis in
the Sacramento-San Joaquin Delta have created an intense demand
for water. Tools and information can be used to help manage the
Central Valley aquifer system, an important State and national
Map of the Central Valley's four major
The Central Valley, also known as the Great Valley of
California, covers about 20,000 square miles and is one of the
more notable structural depressions in the world. Occupying a
central position in California, it is bounded by the Cascade
Range to the north, the Sierra Nevada to the east, the
Tehachapi Mountains to the south, and the Coast Ranges and San
Francisco Bay to the west. The Valley is a vast agricultural
region drained by the Sacramento and San Joaquin Rivers. The
Valley averages about 50 miles in width and extends about 400
mi northwest from the Tehachapi Mountains to Redding.
Generally, most of the valley lies close to sea level and the
land surface has very low relief, but is higher along the
The Central Valley can be divided into two large parts: the
northern one-third is known as the Sacramento Valley and the southern
two-thirds is known as the San Joaquin Valley. The San Joaquin
Valley can be split further into the San Joaquin Basin and the Tulare Basin. The San Joaquin and
Sacramento Valleys meet in the Delta area where the combined
discharge of the Sacramento and San Joaquin Rivers flows
through the Central Valley's one natural outlet, the Carquinez
Strait, on its way to San Francisco Bay and the Pacific Ocean.
Just east of the Delta, several streams issue from the Sierra
Nevada into the valley and flow to the Delta in an area
referred to as the Eastside Streams.