As many as one in five wells worldwide is at risk of running dry if groundwater levels drop by even a few meters, according to a new study appearing Thursday in the journal Science.
Wells supply water for half the world’s irrigated agriculture, as well as drinking water to billions of people. But the aquifers that wells draw from have been imperiled in recent years as intense demand and lack of government management have allowed them to be drained. The scale of the threat has been difficult to calibrate, however, especially at a global level.
Researchers at the University of California, Santa Barbara produced their analysis by compiling construction records for almost 39 million groundwater wells in 40 countries, including their locations, depths, purposes, and construction dates. They found that between 6% and 20% are no more than 5 meters deeper than their local water tables, “suggesting that millions of wells are at risk of drying up if groundwater levels decline by only a few meters,” the authors wrote.
One solution when wells run dry is to dig deeper, but that often leads to poor water quality, according to the researchers. Well construction is also expensive, meaning that digging deeper isn’t always an option.
Global warming and sea level rise due to climate change are also contributing to the problem.
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