IRVINE, Calif., June 16 (UPI) -- Earth's largest water basins aren't in ideal health. According to a new study by Earth scientists at the University of California, Irvine, more than a third of the world's biggest groundwater basins are under distress.
But while measurement trends suggests growing human consumption is depleting some of the world's largest aquifers, scientists say estimates about how much potable water remains are hard to come by.
"Available physical and chemical measurements are simply insufficient," lead researcher Jay Famiglietti, a professor at Irvine and a senior water scientist at NASA's Jet Propulsion Laboratory, explained in a press release. "Given how quickly we are consuming the world's groundwater reserves, we need a coordinated global effort to determine how much is left."
Famiglietti and his colleagues did their best to gauge aquifer health by analyzing data collected by NASA's Gravity Recovery and Climate Experiment satellites. Water weight affects the planet's gravitational forces, so by studying variations in Earth's gravity, scientists can measure water flows.
Of the 37 water basins studied, scientists labeled eight as overstressed -- meaning they weren't receiving any natural replenishment. Another five were also found to be distressed to varying degrees -- in poor health but with some water flowing back in.
Water flows in the Arabian Aquifer System, of the Middle East, and in the Murzuk-Djado Basin, of North Africa, were ranked as the two most distressed water basins. California's Central Valley, while not one of the eight overstressed basins, is America's most damaged aquifer.
Researchers point out that especially dry places are over-reliant on groundwater, and that population growth and global warming are likely to only make things worse.
"What happens when a highly stressed aquifer is located in a region with socioeconomic or political tensions that can't supplement declining water supplies fast enough?" said study author Alexandra Richey, a former UCI doctoral student. "We're trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods."
The health report was accompanied by a second study complaining of the inexact science of measuring aquifer reserves. Satellite data helped researchers get a better idea of what is flowing in and out, but measuring exactly how much is left is another story.
"We don't actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia," Richey said. "In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly."