Lake Mead Reaches Lowest Level Since 1956

LiveScience Staff

Date: 23 September 2010 Time: 12:06 PM ET

In August 2010, the lake level stood at 1,087 feet (331 meters) above sea level.
CREDIT: NASA

Images from the Landsat 5 satellite show changes that have occurred on the eastern end of Lake Mead since 1985. In August 2010, the lake reached its lowest level since 1956.

The largest reservoir in the United States is straining from persistent drought and increasing human demand.

These images show a clear difference in the lake of 1985 and that of 2010. Badger Cove, Driftwood Cove and Grand Wash Bay have receded to become valleys and channels of the Colorado River. The shores around the lake display the "bathtub ring" effect, with a chalky white line appearing where sediments had accumulated below the earlier water levels.

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 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 droughts in the 1950s and the filling of another upstream reservoir, Lake Powell, in the 1960s.

One way to measure the lake's health is the lake level, or water elevation, which stood at 1,087 feet (331 meters) above sea level in late August 2010. In August 1985, the lake level was 1,213 feet (370 meters) above sea level.

Lake Mead reached its August 2010 low after decades of population growth in the American Southwest and 12 years of persistent drought. Approximately 800,000 acre-feet evaporate yearly, and the water flow from the upstream reaches of the Colorado River has been far below normal since the start of the drought in 1998.

As of August 2010, Lake Mead held 10.35 million acre-feet, just 37 percent of the lake's capacity.