Once the largest man-made reservoir in the world, Lake Mead Reservoir in Nevada, has already dropped more than ten vertical feet this year; and it's expected to lose another 10-20 feet before next winter's rain and snow comes. Lake Mead is now about 1,106 feet above sea level. The historic high water mark was 1129 feet above sea level. The lowest pump intake is at 1000 ft. After that, no water for Vegas, baby.
The once mighty 1,450-mile Colorado River that feeds Lake Mead (from Arizona's Lake Powell Reservoir some 180 miles upstream) has nearly disappeared. As it turns out, the 20th Century was one of three wettest centuries during the last 13 centuries in the Colorado Basin. So the prospect of abundant water returning to the Colorado Basin in the future, is slim, to none. That's not accounting for global warming either.
A 14-year drought (since 2000—nearly unrivaled in 1,250 years), has lowered the water level in Lake Mead by more than 90 vertical feet, it's the lowest the reservoir has been in over 40 years. This is the second year in a row that the Colorado River will flow with less than than half of its historic average due to low snowpack in the Rockies, its primary source. According to the Bureau of Reclamation, the overall storage of water in the basin is at 47 percent of capacity, down from 53 percent last year.
If the lake water level drops much more, then, Las Vegas, the Southwest's city of light, will go dark in more ways than one. Intake valves are in danger of being exposed at 1000 feet. That's 106 feet before shut off. Las Vegas (20 million people) gets 90 percent of its water, and 100% of its electricity from the Lake Mead, which is also a crucial source of water for Los Angeles, and for millions of acres of that water irrigates California's Imperial Valley farmlands.
Aerial view. We motored into Castle Cove, near the top of photo (longest finger). Black Canyon & Hoover Dam is at bottom. You can't see Hoover Dam from this photo.
Lake Mead Water Levels — Historical and Current
More on Colorado River & drought.
NASA CA & NV snowpack gif from October 2013 to April 2014.