NEW YORK - From the Arabian Peninsula to northern India to California's Central Valley, nearly a third of the world's 37 largest aquifers are being drained faster than they are being replenished, according to a recent study led by scientists at the University of California, Irvine.
The aquifers hold groundwater, the primary source of fresh water in food-producing regions that support approximately two billion people.
"We're depleting one-third or more of the world's major aquifers at a pretty rapid clip," said Dr Jay S. Famiglietti, a professor of earth system science at UC Irvine, and a leading researcher for the study. "And there's not as much water there as we think."
About 20 per cent of the world's population depend on crops irrigated by groundwater, according to another scientist, Professor Marc Bierkens, who holds a chair in earth surface hydrology at the Department of Physical Geography at Utrecht University in the Netherlands.
"Humans are overexploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America," he wrote in a 2012 study.
The total amount of water in the aquifers, and how long it will last at current depletion rates, is still uncertain. Dr Famiglietti and his colleagues found that eight to 11 of 37 major world aquifers - many of which are in arid or semi-arid regions - are losing much more water than man or nature returns to them.
The new findings do not come as a surprise to hydrologists like Dr Jerad Bales, chief scientist for water at the US Geological Survey. But for him and other experts, an open question is whether the governments and individuals who control groundwater can or will work to gain more knowledge about the extent of the resource and how much use is sustainable.
Another question is whether those with responsibility for managing the aquifers will act to limit groundwater use, particularly if groundwater is essential to their livelihoods.
"Quantifying our understanding of how we use water in the world is very important, especially when the resource becomes limited," Dr Famiglietti said. "It's important to understand where the big users are because that is key to affecting management in the future."
NEW YORK TIMES