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Humans are depleting underground aquifers around the world at alarming rates, threatening hundreds of millions of people who rely on them for survival, according to a comprehensive study conducted by researchers from NASA and the University of California, Irvine.
Twenty-one of the world's 37 largest aquifers are losing water at a greater rate than they're being refilled, falling victim to population growth and climate change. Thirteen of those diminishing water sources are experiencing "significant distress," including the Arabian Aquifer System, which supplies Saudi Arabia, Syria, Iraq, and Yemen, the Murzuk-Djado Basin in northern Africa, the Indus Basin of India and Pakistan, and the Central Valley Aquifer System in California.
"It's very serious," Jay Famiglietti of NASA's Jet Propulsion Laboratory and an author of the report told VICE News. "All over the world, we use more water than we have available to us on a renewable basis."
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The scientists analyzed 10 years of data from NASA's GRACE satellites, which measure anomalies in the Earth's gravity brought about by changes in water supplies.
More than two billion people around the world rely on aquifers as their sole source of drinking water, according to UNESCO. Losing that water can disrupt economies and drive conflicts, particularly in areas of the world that are already unstable, said Charles Iceland of the World Resources Institute.
Syria, for example, experienced its worst drought on history in the years prior to the outbreak of civil war in 2011. Desperate farmers turned to groundwater supplies, which diminished, forcing some of them to flee their homes. An estimated one million rural Syrians relocated to the country's cities. A wide range of researchers and government officials say this massive social dislocation helped feed anti-government sentiment.
Yemen, where water supplies in some urban areas could run dry by the end of the decade, could soon see a similar situation, Iceland said.
"People see the decline in these groundwater levels and they're worried, if they run out of water, populations will have to migrate somewhere else," Iceland told VICE News. "As if there isn't enough problem with state dissolution there, Yemen could fall into even greater chaos."
A 2012 State Department report found that water shortages are likely to contribute to instability in areas crucial to US national security over the next 10 years. Water supply shortages, the department's National Intelligence Council warned, could lead to state collapse, inflame regional tensions, and distract US diplomatic partners from cooperation on shared policy goals.
But while it's clear groundwater is disappearing in many places, no one knows exactly how much water remains in the world's aquifers, making it impossible to know when they might run dry, Famiglietti said. Many are deep underground and in difficult to reach places. So unlike oil and natural gas reserves, accurate estimates of the world's water supply are elusive. For example, projections for when the Northwest Sahara Aquifer System might be entirely depleted range from 10 years to 21,000 years.
In the meantime, dipping ever further into our groundwater sources is wreaking havoc below ground — as well as above.
"There's serious ecological damage being done right now. The ground is sinking in California, streams are being depleted, the water table is falling, wells are running dry, the quality of water is degrading," Famiglietti told VICE News. "We really are past these sustainability tipping points, so it sure as heck would be good to know how much water is left. We're depleting it very quickly."
Follow Laura Dattaro on Twitter: @ldattaro