IMPERIAL VALLEY

intensively irrigated part of the Colorado Desert, mainly in Imperial County, southeastern California, U.S., extending southward for 50 miles (80 km) from the southern end of the Salton Sea (a saline lake) into Mexico. Part of a trough stretching from the Coachella Valley to the Gulf of California, it is almost entirely below sea level (235 feet below at the edge of the Salton Sea) and has a hot desert climate characterized by daily temperature extremes. It was once part of the Gulf, from which it was cut off by the damlike deposits of the Colorado River Delta Fan. Bordered by sand dunes and barren mountains, it was an uninhabited wasteland until the Imperial Canal was opened in 1901 and diverted Colorado River water into the valley through Mexico. Floodwaters in 190507 destroyed the irrigation channels and created the Salton Sea (now maintained by irrigation runoff). Development of the region languished until the completion of the Hoover Dam in 1935 and the All-American Canal in 1940. The valley, with 3,000 miles of irrigation canals, contains about 500,000 acres (200,000 hectares) of cultivated land. Products include truck crops, alfalfa, cotton, sugar beets, and livestock. El Centro, Brawley, Calexico, and Mexicali, Mex., are commercial centres.