COLORADO DESERT, a name applied to that arid re gion of south-eastern California which extends from San Gor gonio pass south-eastward to the Gulf of California, and includes the depression (248.7 ft. below sea level) known as "Salton sink." It is separated from the Mohave desert (q.v.) by the San Bernardino, Cottonwood, Chuckwalla and Chocolate mountains. The Colorado desert is about 200 m. in length and attains a maxi mum width of 5o miles. The northwestern portion consists chiefly of shifting sand dunes but farther southeast, below the sea level, the valley floor is silt-covered and fertile ; the soil of the Imperial valley (q.v.) is highly productive when irrigated. The rainfall varies considerably from year to year, but the aver age is between 3 and 4 in. yearly. During the five summer months the mean daily temperature is high, about 9o° F, and occasionally an extreme of 125° or more in the shade is reached.
See W. C. Mendenhall, Ground Waters of the Indio Region, Cali fornia with a sketch of the Colorado Desert, and Some Desert Water ing Places in South-eastern California and South-western Nevada. These are U.S. Geological Survey Water Supply Papers, nos. 225 and 224, respectively. See also J. Smeaton Chase, California Desert Trails