Las Vegas could run out of water by 2021

Scientists are predicting that Lake Mead, the main source of water for Las Vegas, could run dry in 13 years. Since we're talking about Vegas, scientists put the odds of this happening at 50-50.

The simple reason for the problem is that more water is being taken out of the lake than is being put in. Increased demands for water for to drink and for irrigation, coupled with a long-term drought have reduced the lake's level by 50%.

This problem is not limited to Lake Mead. In central Asia, the Aral Sea - once one of the largest landlocked bodies of water in the world - has shrunk by almost 90%, causing massive environmental problems. Lake Chad, one of Africa's largest lakes, is also rapidly shrinking.