Alarming Water Resource Loss in Middle-East Observed From Space

The alarming fact that large parts of the arid Middle East region lost freshwater reserves rapidly during the past decade is highlighted by a study based on data from a pair of gravity-measuring NASA satellites.

Scientists at the UC Irvine and NASA estimate that during the seven-year period beginning in 2003, parts of Turkey, Syria, Iraq and Iran along the Tigris and Euphrates river basins lost 144 cubic kilometers of its total stored freshwater, which is comparable (in quantity, not quality) to the amount of water in the Dead Sea. The researchers attribute about 60 percent of the loss to pumping of groundwater from underground reservoirs.

The study will be published in the journal Water Resources Research on February 15, and will be 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 especially useful when hydrological 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 Prof. Jay Famiglietti, main investigator of the study and a hydrologist 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."

GRACE is able to measure gravity very precisely, so that the satellites can even sense the small changes caused by a changing level of water reservoirs. Of course, one cubic kilometer of water is quite the heavy weight all by itself, having a mass of exactly one billion tons. But compared to the mass of the surrounding stones and overall mass of our planet, the relative gravity force of the water is still small and requires a very precise instrument like GRACE, which is periodically measuring the gravity regionally to record a region's water storage changes over time.

The space data is making sense in the context of what happens on the ground. Famiglietti points out that 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 very 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," continues Famiglietti. "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."

Study co-author Matt Rodell of NASA's Goddard center says it is important to remember groundwater is being extracted unsustainably in parts of the United States, as well.

"Groundwater is like your savings account," Rodell said. "It's okay to draw it down when you need it, but if it's not replenished, eventually it will be gone."