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
Glen Canyon Dam long fight, the USBR agreed not to build the dam in Dinosaur National Monument, but only if the environmentalists did not oppose the proposed dam in Glen Canyon. Since first filling to capacity in 1980, Lake Powell water levels have fluctuated greatly depending on water demand and annual runoff. Operation of Glen Canyon Dam helps ensure an equitable distribution of water between the states of the Upper Colorado River Basin (Colorado, Wyoming, and most of New Mexico and Utah) and the Lower Basin (California, Nevada and most of Arizona). During years of drought, Glen Canyon guarantees a water delivery to