The Water Authority is one of Metropolitan Water District of Southern California’s member agencies, and its largest purchaser of water. Formed in 1928 to develop, store, and distribute supplemental water in Southern California for domestic and municipal purposes, MWD now supplies water to approximately 19 million people in a service area that includes portions of Ventura, Los Angeles, Orange, San Bernardino, Riverside and San Diego counties. The MWD service area covers a 70-mile-wide strip of the Southern California coastal plain, extending from the city of Oxnard on the north to the Mexican border. Close to half of the water used in this 5,200-square -mile region is supplied by MWD, and about 90 percent of its population receives at least some of its water from MWD.
MWD obtains its water from two sources: the Colorado River and the State Water Project. The extent to which MWD's member agencies rely upon MWD supplies varies. The ability of MWD to provide supplies in a given year may depend upon the extent to which member agencies exercise their respective preferential rights to purchase water.