NASA/EO - Lake Mead At Lowest Levels Since 1956

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1985


2010

In August 2010, Lake Mead reached its lowest level since 1956. The largest reservoir in the United States was straining from persistent drought and increasing human demand.

Two images from the Thematic Mapper on the Landsat 5 satellite show some of the stark changes on the eastern end of the lake since 1985. Badger Cove, Driftwood Cove, and Grand Wash Bay have receded to become valleys and channels of the Colorado River, which flows in from the east (image right). The shores around the lake display the “bathtub ring” effect, with a chalky white outline marking new shoreline where sediments had previously accumulated below the water.

Located on the Colorado River, east of Las Vegas and west of the Grand Canyon, Lake Mead provides power and water for human activities in Nevada, Arizona, southern California, and northern Mexico. The reservoir grew up behind the Hoover Dam when it was built in the 1930s, and it can hold the equivalent of the entire flow of the Colorado River for two years.

The maximum capacity of Lake Mead is 28.5 million acre-feet (35 cubic kilometers) of water, with an acre-foot equaling the amount required to cover one acre to a depth of one foot. According to records from the U.S. Bureau of Reclamation, the lake held roughly 27.8 million acre-feet of water at its high point in 1941, and levels have fluctuated through drought in the 1950s and the filling of another upstream reservoir, Lake Powell, in the 1960s. Lake levels rose steadily through the 1980s, reaching 24.8 million acre-feet in August 1985, when the bottom image was taken. But as of August 2010 (top image), Lake Mead held 10.35 million acre-feet, just 37 percent of the lake’s capacity.

EDIT

http://earthobservatory.nasa.gov/IOTD/view.php?id=45945