Scientists uncovered the water depletion by conducting one of the first comprehensive and publicly available sets of hydrological measurements of the area. Over a seven-year period beginning in 2003, sections of Turkey, Syria, Iraq and Iran lost 144 cubic kilometers (117 million acre feet) of water – about the equivalent of all the water in the Dead Sea. The scientists attribute the bulk of the loss—some 60 percent—to pumping of water from underground reservoirs.
Using measurements from the Gravity Recovery and Climate Experiment (GRACE) satellites, researchers at the University of California, Irvine, NASA and the National Center for Atmospheric Research have identified the Tigris and Euphrates River Basin as having the second fastest rate of groundwater storage loss, after India. In the Middle Eastern region, “GRACE data show an alarming rate of decrease in total water storage,” the scientists report in a paper accepted for publication in Water Resources Research, a journal of the American Geophysical Union. The study will publish on 15 February.
The GRACE mission, which NASA launched in 2002 to measure the earth’s local gravitational pull from space, is providing a global picture of trends in water storage, said Jay Famiglietti, principal investigator of the new study and a hydrologist and UC Irvine professor of Earth System Science.
GRACE is “like having a giant scale in the sky,” he said. Within a region, rising or falling water reserves alter the Earth’s mass in a particular region, influencing how strong the local gravitational attraction is. By periodically measuring the gravity regionally, the satellites provide information about how much each region’s water storage changes over time.
“GRACE is really the only way we can estimate groundwater storage changes from space right now,” Famiglietti said. “Whenever you do international work, it’s exceedingly difficult to obtain data from different countries. For political, economic, or security reasons, neighbors don’t want each other to know how much water they’re using. In regions like the Middle East, where data are relatively inaccessible, satellite observations are one of the few options.”
The 754,000-square-kilometer (291,000-square-mile) Tigris and Euphrates basin jumped out as a hotspot when UC Irvine researchers looked at the global water ups and down, Famiglietti said. Within the seven-year period of GRACE data they analyzed, he and his colleagues calculated that water storage in the region shrunk by an average of 20 cubic km (16 million acre feet) a year. “This rate of water loss is among the largest liquid freshwater losses on the continents,” the authors wrote in the study, noting it was especially striking after a drought afflicted the region in 2007. Meanwhile, the region’s demand for fresh water is rising, Famiglietti noted.
From the satellite measurements of decreasing water storage, he and his colleagues 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 reservoirs accounted for about another fifth of the decline. Looking at those results and the GRACE data, they determined that the majority of water loss - approximately 90 cubic km (73 million acre feet) over the seven-year period – was due to reduced groundwater.
When a drought shrinks the available surface water supply, irrigators and others turn to groundwater, Famiglietti said. The Iraqi government drilled about 1,000 wells in response to the 2007 drought, but that doesn’t include the numerous private wells that landowners very likely drilled as well.
Water management is a complex issue in the Middle East, “an area that already is dealing with limited water resources and competing stakeholders,” said Kate Voss, lead author of the study and a water policy fellow with the University of California’s Center for Hydrological Modeling in Irvine, which Famiglietti directs.
Turkey controls the Tigris and Euphrates headwaters, as well as the reservoirs and infrastructure of Turkey’s Greater Anatolia Project, which dictates how much water flows downstream into Syria and Iraq, the researchers note. And due to different interpretations of international laws, the Tigris and Euphrates basin does not have coordinated water management. Turkey’s control of how much water flows into neighboring countries has already caused tension, such as during the 2007 drought, when Turkey continued to divert water to irrigate agricultural land, the scientists state.
“That decline in streamflow put a lot of pressure on northern Iraq,” said Voss. “Both the UN and anecdotal reports from area residents note that once streamflow declined, this northern region of Iraq had to switch to groundwater. In an already fragile social, economic and political environment, this did not help the situation.”
Famiglietti, Voss and two colleagues from UC Irvine are visiting another Middle Eastern region beginning on 18 February, on a “science diplomacy” trip to Israel, Palestine and Jordan. One goal of the trip is to simply raise awareness and share their data about groundwater depletion, which is also a serious issue in the three countries they will visit. While the researchers hope to establish collaborations with local groups to measure aquifers on site, the trip is also a chance for the American scientists to learn about some of the water-efficiency practices in arid regions, Famiglietti said.
“They just do not have that much water to begin with, and they’re in a part of the world that will be experiencing less rainfall with climate change. Those dry areas are getting dryer,” Famiglietti said. “They and everyone else in the world’s arid regions need to manage their available water resources as best they can.”
“Groundwater depletion in the middle east from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region”Authors:
Peter Weiss | American Geophysical Union
Tornadoes occurring earlier in “Tornado Alley”
17.09.2014 | American Geophysical Union
Meteorite That Doomed Dinosaurs Remade Forests
17.09.2014 | University of Arizona
17.09.2014 | Veranstaltungen
17.09.2014 | Veranstaltungen
17.09.2014 | Veranstaltungen