LAKE MEAD NRA, AZ - JULY 30: (FILE PHOTO) On Sunday, October 9, 2011, The Hoover Dam Went On Line 75 Years Ago In The USA Please refer to the following profile on Getty Images Archival for further ... more 
LAKE MEAD NRA, AZ - JULY 30: (FILE PHOTO) On Sunday, October 9, 2011, The Hoover Dam Went On Line 75 Years Ago In The USA Please refer to the following profile on Getty Images Archival for further imagery. http://www.gettyimages.co.uk/Search/Search.aspx?EventId=103884936&EditorialProduct=Archival# A plaque marks the dividing line between the states of Arizona and Nevada at the Hoover Dam July 30, 2007 in the Lake Mead National Recreation Area, Arizona. The white "bathtub ring" on the rocks around Lake Mead in the background is from mineral deposits left by higher levels of water. A seven-year drought and increased water demand spurred by explosive population growth in the Southwest has caused the water level at Lake Mead, which supplies water to Las Vegas, Arizona and Southern California, to drop over 100 feet to its lowest level since the 1960s. The National Park Service has been forced to close or extend boat launch ramps, and move entire marinas to try to keep up with the receding water levels. Because the water at the lake, the largest man-made reservoir in North America, isn't being replenished as fast as it's being used, water managers are now working to come up with plans to combat the effects of continued population growth, drought and a dwindling supply of water from the Colorado River due to climate change. (Photo by Ethan Miller/Getty Images) less 
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Getty Images | Photo By Ethan Miller / Getty Images
Fri, Oct 7, 2011 9:01 AM EDT