Two new studies show that current groundwater use has reached unsustainable levels, a “tipping point’ that threatens to undermine regional water security.

The new studies, published in Water Resource Research, indicate that upwards of 35% of the world’s 37 largest aquifers are in a state of “significant distress,” and are being depleted by human activity quicker than they can be naturally recharged. Scientists aren’t entirely sure how much groundwater remains within these basins, which means a sizable portion of our planet’s inhabitants are consuming this finite resource without a clear sense as to when it might run out.

Click to emiggen. A larger version of this map can be found here.

“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?” asked UCI doctoral student Alexandra Richey in a NASA-JPL statement. “We’re trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods.”

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Richey, who was the lead author on both studies, says that climate change and population growth will only exacerbate the problem. And as the current situation in California attests, the burden placed on groundwater during times of drought can be intense.

The first study, which took gravity measurements taken by NASA’s twin GRACE satellites, shows that eight of the big groundwater basins are “overstressed,” with no natural replenishment to offset usage. Five aquifers are classified as “extremely” or “highly” stressed owing to various rates of recharge.

Unsurprisingly, the driest regions in the world are home to the most overburdened aquifers. The three most stressed basins are the Arabian Aquifer System (a source of water to 60-million people), the Indus Basin aquifer of northwestern India and Pakistan, and the Murzuk-Djado Basin in North Africa. California’s Central Valley was designed as highly stressed.

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In the second study, the researchers conclude that the amount of useable water left in these reservoirs is unknown.

“We don’t actually know how much is stored in each of these aquifers,” says Richey. “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.”

You can find the studies here and here, both of which were published in the science journal Water Resources Research.

[ NASA JPL ]


Contact the author at george@io9.com and @dvorsky. Top image by UC Irvine/NASA/JPL-Caltech