Lake Mead, the largest reservoir in the United States that stores water for tens of millions of people and countless acres of farmland in the southwest, is shrinking at a terrifying rate and now stands just one quarter full. "Everyday someone's ripping a drive off because last week, where there was no rock, it's now a foot down or two feet down, so things are exposed," says boatseller Jason Davis. Climatologists say two decades of drought is not unheard of in the western United States, but combined with human-caused global warming, it is transforming the region. IMAGES AND SOUNDBITES ARRANGED IN SEQUENCES (completes 32DM99G_EN)