By Chris Arsenault
ROME, June 17 (Thomson Reuters Foundation) - Human water use is sucking dry around a third of the world's largest underground water basins at an alarming rate, with potentially risky consequences for farmers and other consumers, researchers said.
Eight of the planet's 37 biggest aquifers are classified as "overstressed" because they have almost no new water flowing in to offset usage, according to two studies from the University of California based on NASA satellite data.
Another five aquifers are classified as "highly stressed", meaning some water is flowing back into them but they are still in trouble, said the studies published in the journal Water Resources Research this week.
Aquifers become stressed when too much water is taken out for household, agricultural and industrial use, and not enough surface water seeps in to replenish the underground rock formations.
The Arabian Aquifer System, a key water source for 60 million people in Saudi Arabia, Iraq, Qatar, Syria and other countries, is the world's most overstressed, the research said.
The Indus Basin aquifer in northwestern India and Pakistan is the second most vulnerable, and the Murzuk-Djado Basin in north Africa is the third.
All of these regions are already suffering from varying degrees of political strife, and water scarcity will invariably intensify social problems, the researchers said.
"We are trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods," Alexandra Richey, lead author of both studies, said in a statement.
The most overburdened aquifers are in some of the world's driest areas, which depend on groundwater as there isn't enough rainfall for crops and human needs.
In California, where a drought has wrought havoc on farmers and homeowners, the Central Valley aquifer was labelled as highly stressed and suffering from rapid depletion. But the situation is worse in other places like the Middle East or North Africa, the studies said.
Scientists do not know exactly how much groundwater remains in the aquifers.
"In a water-scarce society, we can no longer tolerate this level of uncertainty, especially since groundwater is disappearing so rapidly," Richey said.
The studies are the first to examine groundwater losses with data from outer space. They measured bumps in the Earth's gravity, which are affected by the weight of water in different regions.
(Reporting By Chris Arsenault; editing by Megan Rowling; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit www.trust.org)