The Colorado River is one of the major rivers in the Western United States. Its watershed encompasses part of seven U.S. states and two Mexican states. It is a vital source of water for 40 million people. Major dams on the river generate hydroelectric power for much of the Intermountain West. In most years its entire flow is diverted for agricultural irrigation and domestic water supply. Intensive water use has dried up the lower 100 miles of the river, which since the 1960s has rarely reached the sea.