Minimize Qadisiyah Reservoir, Iraq

This natural-colour image was acquired on 15 September 2009 by the Landsat 5 satellite and shows the shrinking of the Qadisiyah Reservoir in Iraq.

For comparison, also see the image acquired on 07 September 2006 by Landsat 5, which highlights the scale of the shrinking.

Scientists using the twin gravity-measuring satellites of the Gravity Recovery and Climate Experiment (GRACE) have found that a large portion of the Middle East lost freshwater reserves rapidly during the past decade. The research team observed the Tigris and Euphrates river basins-including parts of Turkey, Syria, Iraq, and Iran-and found that 117 million acre feet (144 cubic kilometres) of fresh water was lost from 2003 to 2009. That amount is roughly equivalent to the volume of the Dead Sea. About 60 percent of the loss was attributed to the pumping of groundwater from underground reservoirs.

"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, principal investigator of the study. "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."

Obtaining ground-based data in Middle East can be difficult, so data from satellites such as GRACE are essential to providing a global picture of water storage trends. Within any given region on Earth, rising or falling water reserves alter the planet's mass, influencing the gravity field of the area. By periodically measuring gravity in each region, the GRACE satellites tells us how water storage changes over time. (To learn more about GRACE's ability to study fresh water on Earth, read The Gravity of Water.)

The researchers calculated that about one-fifth of the water losses in their Tigris-Euphrates study region came from snowpack shrinking and soil drying up, partly in response to a 2007 drought. Loss of surface water from lakes and reservoirs accounted for another fifth of the losses. The majority of the loss-approximately 73 million acre feet (90 cubic kilometres)-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.

View the full resolution image.

Credit: NASA Earth Observatory


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