Central Valley

The Central Valley is a great trough of central California. It is about 720 km (450 miles) long and some 80 km (50 miles) wide and was first seen by Spanish explorers in the 1500's. It remained virtually uninhabited until the California gold rush of 1849. Irrigation was introduced in the 1880's.

The Central Valley lies between the Sierra Nevada and the Coast Ranges.

The Sacramento and San Joaquin rivers drain most of the valley before they converge in a huge delta and flow into San Francisco Bay. The delta is California's leading truck-farming and horticultural area and the Central Valley is California's agricultural heartland, although the region's urban and suburban areas have expanded dramatically since the 1970's. The Central Valley boasts a long growing season and fertile soil. As a result, it has the largest single concentration of fruit and nut farms and vineyards in the United States. Cotton, grain and several sorts of vegetables are also grown there.

Precipitation in the region ranges from 76 cm (30 inches) in the north to 15.2 cm (6 inches) in the south. About 60% of the valley's agricultural land is in the south, while 60% of its water is in the north. That problem was addressed by the Central Valley Project, which brings water from the Sacramento basin in the north into the San Joaquin Valley in the south, which includes Fresno and Tulare counties, the two leading U.S. agricultural regions.

In the extreme south of the Central Valley is the dry, alkaline Tulare Lake basin, which is almost totally unsuitable for irrigation. Oil extraction and refining, as well as petrochemical production are also important to the region's economy.