CREDIT: Daryl Peveto / LUCEO for The Wall Street Journal.Photo Assignment ID: 11416 Slug: LAKEMEAD ..Lake Mead, Nevada, March 16, 2011 - A portrait of Patricia Mulroy, General Manager of the Southern Nevada Water Authority. ..Lake Mead is the largest water reservoir in the United States. Located on the Colorado River southeast of Las Vegas, it is the major reserve for Nevada, California and Arizona. The city of Las Vegas alone gets 90% of its water from Lake Mead. The lake is currently experiencing a ten year drought, recently dropping to1,083 feet - its lowest level since it was dammed in the 1930s. If it drops further, there is the potential for cutoffs of water for hydro-electricity, agriculture and cities across the Southwest. The current level is near emergency level: if drops to 1075, the Secretary of Interior will have to declare a severe water emergency and major cutbacks will ensue. If gets below 1025, all water for hydro from Hoover Dam shut off. If it falls below 1,000 feet the intake valves that pull water from the Lake for consumption will no longer be operational.