About a third of the world’s largest groundwater basins, including California’s Central Valley, are being depleted by human consumption, but researchers say little accurate data exists on how much water is left in them, according to a pair of UC Irvine studies released Tuesday.
“Available physical and chemical measurements are simply insufficient,” said UCI professor Jay Famiglietti, also the senior water scientist at NASA’s Jet Propulsion Laboratory.
“Given how quickly we are consuming the world’s groundwater reserves, we need a coordinated global effort to determine how much is left.”
Researchers estimated groundwater supplies in major basins using data from NASA’s Gravity Recovery and Climate Experiment, or GRACE, satellites, which measure changes in Earth’s gravity that can be affected by water masses. According to the study, 13 of the planet’s 37 largest aquifers studied between 2003 and 2013 are being depleted and receiving little to no recharge.
Eight were classified as “overstressed,” while five others were labeled “extremely” or “highly” stressed, depending on the level of replenishment.
The Arabian Aquifer System, which provides water for more than 60 million people, was found to be the most overstressed in the world, according to the study. The Indus Basin in northwestern India and Pakistan was second- worst, followed by the Murzuk-Djado Basin in northern Africa.
The California Central Valley aquifer, which is heavily used for agriculture, was labeled as “highly” stressed.
Researchers noted in a companion study that estimates vary widely on the amount of useable groundwater remaining around the world. For the Northwest Sahara Aquifer System, estimates on the amount of time left until the basin is depleted vary from 10 years to 21,000 years, according to the report.
“We don’t actually know how much is stored in each of these aquifers,” said Alexandra Richey, the lead author on both studies who conducted the research as a UCI doctoral student. “Estimates of remaining storage might vary from decades to millennia. In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly.”
— City News Service