H2O

40 million people, not including Mexico, count on the water from the Colorado basin. When the water from the river is overburdened, water is retrieved from the groundwater. Since December 2004, the basin of the Colorado River has lost nearly 53 million acre feet of freshwater, almost double the volume of the region's largest reservoir, Nevada's Lake Meade, researchers say. About 75 percent of the total--about 421 million acre feet--came from groundwater, the study by author Stephanie Castle found.
"We don't know exactly how much groundwater we have left, so we don't know when we are going to run out," Castle said. "This is a lot of water to lose."