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Lake Mead
Hoover Dam's reservoir on the Colorado River, now at record lows
When full, Lake Mead holds about 26 million acre-feet (32 km³) of Colorado River water, the largest reservoir in the United States by capacity. It last came close to full in 1983. The lake formed behind Hoover Dam beginning in 1935, flooding about 112 miles (180 km) of canyon on the Nevada-Arizona line and drowning the Mormon farm town of St. Thomas, whose foundations reappear whenever the water drops. It was named for Elwood Mead, the Bureau of Reclamation commissioner who oversaw the dam, and in 1936 its shores became the country's first national recreation area.
The reservoir is a savings account for the Lower Colorado Basin. Its water supplies most of the Las Vegas area and flows on to farms and cities in Arizona, California and Mexico. Since 2000 a long drought and steady overuse have drained it. In 2022 it fell to about 1,040 feet (317 m) above sea level, exposing sunken boats and long-hidden human remains. That record did not last. In August 2026 Lake Mead sank below its 2022 low, and on September 16, 2026, Reclamation measured it at 1,038.5 feet (316.5 m), about a quarter of active capacity and nearly 190 feet below its 1983 peak.
Shortage rules adopted in 2007 and 2019 have already cut Arizona's and Nevada's deliveries, and the Bureau of Reclamation's 2026 studies project the lake to keep falling into 2027. Las Vegas now draws from a deep third intake completed in 2020 so it can keep pumping even at very low levels. The seven basin states and the federal government are negotiating new operating rules for the river after 2026, and the outcome will decide how much more of the reservoir's bathtub ring is exposed.