Some of America's -- and the world's -- biggest bodies of water are drying up, threatening the water supply and livelihoods of millions

Scientists from the Scripps Institution of Oceanography in San Diego say that Lake Mead, the largest man-made lake and reservoir in the United States, which supplies water as well as hydroelectric power to tens of millions of people throughout the Southwest, could be dry in just 13 years. But Lake Mead is just one of a number of lakes throughout the world that are imperiled. Large and small bodies of water from Australia to Chile to China to Kenya to Central Asia to South Carolina are sadly deteriorating because of drought, global warming, chemical pollution, increased water demand, excessive fishing and other factors. A look at some of the lakes most at risk. <b>Lake Mead Nevada, U.S.A.</b> Boats are moored at the Lake Mead Marina. The white 'bathtub ring' on the rocks is from mineral deposits left from when the area was underwater. Largely due to climate change, Lake Mead's water level has been decreasing for the last eight years, and Scripps Institution of Oceanography scientists estimate that the reservoir's level could drop too low to allow hydroelectric power generation within just nine years. Photo: Ethan Miller / Getty Images