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Data from gravity-measuring satellites show rapid loss of freshwater reserves during the past decade
Scientists at the University of California at Irvine (UC Irvine); NASA's Goddard Space Flight Center in Greenbelt, Md.; and the National Center for Atmospheric Research in Boulder, Colo., found during a seven-year period beginning in 2003, parts of Turkey, Syria, Iraq and Iran along the Tigris and Euphrates river basins lost 117 million acre ft (144 cu km) of their total stored freshwater. That is almost the amount of water in the Dead Sea. The researchers attribute about 60% of the loss to pumping of groundwater from underground reservoirs.
The findings, published Feb. 15 in the journal Water Resources Research, are the result of one of the first comprehensive hydrological assessments of the entire Tigris-Euphrates-Western Iran region. Because obtaining ground-based data in the area is difficult, satellite data, such as that from NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites, are essential. GRACE is providing a global picture of water storage trends and is invaluable when hydrologic observations are not routinely collected or shared beyond political boundaries.
"GRACE data show an alarming rate of decrease in total water storage in the Tigris and Euphrates river basins, which currently have the second fastest rate of groundwater storage loss on Earth, after India," said Jay Famiglietti, principle investigator of the study and a hydrologist and professor at UC Irvine. "The rate was especially striking after the 2007 drought. Meanwhile, demand for freshwater continues to rise, and the region does not coordinate its water management because of different interpretations of international laws."
The team calculated that about one-fifth of the observed water losses resulted from soil drying up and snowpack shrinking, partly in response to the 2007 drought. Loss of surface water from lakes and reservoirs accounted for about another fifth of the losses. The majority of the water lost — approximately 73 million acre feet (90 cu km) — was due to reductions in groundwater.
"That's enough water to meet the needs of tens of millions to more than a hundred million people in the region each year, depending on regional water use standards and availability," Famiglietti said.
Famiglietti said when a drought reduces an available surface water supply, irrigators and other water users turn to groundwater supplies. For example, the Iraqi government drilled about 1,000 wells in response to the 2007 drought, a number that does not include the numerous private wells landowners also likely drilled.
"The Middle East just does not have that much water to begin with, and it's a part of the world that will be experiencing less rainfall with climate change," Famiglietti said. "Those dry areas are getting dryer. The Middle East and the world's other arid regions need to manage available water resources as best they can."
GRACE is a joint mission with the German Aerospace Center and the German Research Center for Geosciences, in partnership with the University of Texas at Austin. Click here and here for more about GRACE.