Depletion of World Aquifers Worse than Feared, UCI Scientists Find

About one-third of the world’s largest groundwater basins, including California’s Central Valley, are being depleted by human consumption, but researchers say there is little accurate data on how much water is left in them, according to a pair of UC Irvine studies released today.

Of the 37 aquifers studied, 21 are at a tipping point where more is being drawn out than is being replenished, and “13 are i“13 are in really, really bad trouble,” UCI professor James Famiglietti told City News Service.

“We’re kidding ourselves that it’s great and everything is fine,” according to Famiglietti, who is also the senior water scientist at NASA’s Jet Propulsion Laboratory. “Our groundwater supply is at risk because we’re not managing it properly, and we’re acting like we have unlimited water out there, and, of course, that’s not true.”

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, 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.”

Famiglietti compared the problem to someone writing checks on an account while not knowing how much money is in the bank.

The best way to find out what we have is by drilling, but that’s “very, very expensive,” he said.

It could cost about $1 billion in the United States alone to drill into the aquifers to see what’s left, he said. It has been done to increase the oil supply, however, so it should be done for the water supply, Famiglietti said.

“We’re in trouble, and it’s not just California. It’s all over the world,” Famiglietti said.

Desalination could be a solution for the shrinking water supply, but it is “very expensive” and there’s the unresolved problem of what to do with the brine because it’s “pretty toxic” and unwise to throw back into the ocean, the professor said.

“The bigger issue is it’s not enough,” Famiglietti said.

Recycled wastewater also helps, but it is not enough either, the professor said.

“The easiest thing for us to do -- and the cheapest and sensible thing to do -- is to just use less,” Famiglietti said.

Improving the efficiency of agricultural watering and reconsidering our choice of crops would be better ways to address the problem, Famiglietti told CNS.

City News Service

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