Water fountains in front of Hotel Bellagio, Las Vegas. The city exceeded the capacity of its own groundwater field several decades ago, and currently is 90% dependent on a limited allotment from the Colorado River-an allotment it's fast outgrowing. A major prolonged drought combined with rapid population growth in nearby urban areas like Las Vegas, has stressed Lake Mead and the rest of the Colorado River Basin, which provides water to farmers and cities from Colorado to Southern California.