A new study based on NASA satellite measurements reveals what researchers called a shocking loss of groundwater in the Southwest's largest river basin.
The study released Thursday by NASA and the University of California, Irvine says the Colorado Basin has lost enough water since 2004 to supply more than 50 million households for a year. It says more than 75 percent of that loss is groundwater.
The basin supplies water to about 40 million people in seven states as well as people in Mexico.
Lead author Stephanie Castle and fellow researchers say the losses raise further questions about the long-term sustainability of the basin's water supplies to the Southwest and Mexico.
The basin encompasses parts of California, Arizona, Colorado, New Mexico, Nevada, Utah, and Wyoming.