Worlds largest groundwater sources in danger, study

The earth’s largest groundwater basins are being depleted quickly than previously thought, according to two new studies by the University of California, Irvine (UCI).

The studies used information from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites assembled between 2003 and 2013 to examine the 37 largest aquifers on the planet.

Twenty one of those aquifers have gone over their sustainability “tipping points,” meaning they are losing more water every year than is being naturally replenished through processes like rainfall or snow melt, said Jay Famiglietti, senior water scientist at NASA Jet Propulsion Laboratory and main investigator in the two studies.

According to a statement from UCI, out of those 21, eight were found to be “overstressed,” meaning there is “nearly no natural replenishment” to restore water used by humans. Another five were designated “extremely or highly stressed,” indicating that they are “still in trouble” but have “some water flowing back into them.”

Among those classified as “highly stressed” is the California Central Valley Aquifer System. In dry seasons, groundwater typically supplies 46 percent or more of the state’s water, according to the California Department of Water Resources. California is now in its fourth year of exceptional drought. Many communities rely on groundwater exclusively for their water needs, the department noted.

The world’s most overstressed groundwater source, according to researchers, is the Arabian Aquifer System, which supplies water to more than 60 million people.
Researchers used readings from NASA’s two GRACE satellites, which measure variations in the earth’s gravitational pull, Famiglietti told The Huffington Post. When an area either gains or loses a large amount of water, the change in mass allows the satellites to pick up the difference in the gravitational pull. This lets researchers establish the rate at which large aquifers are being depleted.

Although scientists are able to ascertain how fast the water is being depleted, they do not know exactly how much is left.
It would be possible to determine the present groundwater supply by drilling into the aquifers, Famiglietti stated, but scientists currently do not have enough funds to do that.

On the contrary, he believes it is important to determine the exact amount of water still in the ground.
“Given how quickly we are consuming the world’s groundwater reserves, we need a coordinated global effort to determine how much is left,” he mentioned in the UCI statement.