This NASA study looks specifically at the Colorado River Basin and to quote one of the study’s authors,
“The Colorado River Basin is the water lifeline of the western United States,” said senior author Jay Famiglietti, senior water cycle scientist at NASA’s Jet Propulsion Laboratory.
He said the basin, like others worldwide, was relying on groundwater to make up for the limited surface-water supply.
“We found a surprisingly high and long-term reliance on groundwater to bridge the gap between supply and demand,” he said.
“Combined with declining snowpack and population growth, this will likely threaten the long-term ability of the basin to meet its water allocation commitments to the seven basin states and to Mexico,” Famiglietti said.