Many of Earth's groundewater basins run deficits

While GRACE provides valuable information about how global groundwater has changed, it can't measure exactly how much water is left in the aquifers, says Gordon Grant, a hydrologist at the U.S. Department of Agriculture Forest Service in Corvallis, Ore.  Despite that shortcoming, the new work "allows us to put our arms around the volumes of water that are in play and better understand, like an accountant would, withdrawals and deposits of groundwater around the world," he says.