Lake Mead and downstream releases from the dam also provide water for both municipal and irrigation uses . Water released from the Hoover Dam eventually reach several canals . The Colorado River Aqueduct and Central Arizona Project branch off Lake Havasu while the All @-@ American Canal is supplied by the Imperial Dam . In total , water from the Lake Mead serve 18 million people in Arizona , Nevada and California and supply the irrigation of over 1 @,@ 000 @,@ 000 acres ( 400 @,@ 000 ha ) of land .