Nature (July 25, 2014) — Researchers have been tracking the basin's groundwater supply using measurements of well-water levels for some time, and the satellite data are in line with those. The results confirm that groundwater overdraft is a problem throughout the western United States, says Jay Lund, a water-resource engineer and director of the Center for Watershed Sciences at the University of California, Davis. The problem is magnified by the fact that the groundwater is being removed from the ground faster than nature can replenish it. And as it dwindles, the cost to pump rises because the water has to come from greater depths. “At some point, it becomes more costly than it's worth,” says Lund.