An analysis of satellite images taken by NASA Gravity Recovery and Climate Experiment revealed that humans are rapidly consuming the world's groundwater reserves. The researchers are concerned that it might not be long before the water runs out. Findings of the study were published in the June 16 issue of Water Resources Research.
Researchers at the University of California, Irvine, looked at the satellite images of Earth's 37 largest aquifers between 2003 and 2013. They found that eight of the reserves are considered overstressed or have reached their limit so that there is no way to replenish the lost supply. About 60 million people depend on these reserves for water supply.
Five are close to the limit and are described as extremely or highly stressed. Some of the identified highly stressed reserves are located in northwestern India, Pakistan and northern Africa. California's Central Valley is also on the list, with agriculture as the main cause of water depletion.
"As we're seeing in California right now, we rely much more heavily on groundwater during drought," said UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA's Jet Propulsion Laboratory, in a university news release. "When examining the sustainability of a region's water resources, we absolutely must account for that dependence."
The researchers are worried that climate change and population growth could make the groundwater supply problem worse. Unfortunately, they don't have sufficient data to estimate how much water is left in the reserves.
"We don't actually know how much is stored in each of these aquifers. Estimates of remaining storage might vary from decades to millennia," said Alexandra Richey, study lead author who conducted the research as a UCI doctoral student. "In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly."
