Course of the Colorado River Lake Mead, formed by the -high Hoover Dam about southeast of Las Vegas, Nevada, is the largest reservoir in the United States with a full capacity of and a water surface of nearly . However, the lake has not been full for many years due to a combination of drought and increased water usage by Colorado River Basin states. Situated in the Lake Mead National Recreation Area, Lake Mead is a popular recreation site – visited by almost 8 million people a year – and a critical source of water for the Las Vegas metropolitan area, Central Arizona and Southern
Colorado River affected by upstream diversions and reservoir evaporation, especially after the completion of the Colorado River Storage Project in the 1970s. Prior to the completion of Glen Canyon Dam in 1964, the average discharge recorded between 1912 and 1962 was , per year. The drainage basin or watershed of the Colorado River encompasses of southwestern North America, making it the seventh largest on the continent. About , or 97 percent of the watershed, is in the United States. The river and its tributaries drain most of western Colorado and New Mexico, southwestern Wyoming, eastern and southern Utah, southeastern Nevada and California,