Forty million people rely on water released from Lake Mead, on the Colorado River not far from Las Vegas. That booming city, renowned for vice, is also a world leader in water conservation. 

Far downstream huge canals de-water the river, as farmers look to technology to maintain their productivity, Californians deliver water to their vast population and farmland, and Mexico receives its entitlement. The once-great river and vast wetlands face a dried-out channel.