A pair of orbiting satellites, surveying Earth’s water in unprecedented detail, have discovered sharp water decreases in parts of Africa over the past five years.
Scientists from the U.S. National Aeronautics and Space Administration (NASA) and the University of California, Irvine, presented their findings December 12 to a meeting of the American Geophysical Union in San Francisco.
“This is the first time we have been able to track these variations,” Jay Famiglietti, an Earth system sciences professor at UC-Irvine, said. “It’s a very sensitive indicator of climate change.”
The Gravity Recovery and Climate Experiment (GRACE) satellites, launched in 2002, detect the gravitational pull of water, measuring snow, ice, and water in surface bodies and in soils and aquifers. Researchers are using their nearly five-year data record to estimate seasonal water storage variations in more than 50 river basins that cover most of the Earth’s land area.
Congo, Zambezi, Nile basins seen drying
The partnership between NASA and the German Aerospace Center has found that, over a three-year period, water storage along Africa’s Congo River Basin has decreased by nearly twice the amount Africans consume annually, excluding irrigation, Famiglietti said.
The GRACE data also found drying along the Zambezi and Nile basins in Africa, with corresponding increases along the American Mississippi and Colorado River basins.
“We know that things go up and down so there is no cause for alarm,” Famiglietti said, adding that scientists need a longer period of data to make more definitive conclusions.
NASA said such information is vital for managing water resources in vulnerable parts of Africa and Southeast Asia, since increasing populations and standards of living place demands on water resources that are often unsustainable. The data can be used to make more informed regional water management decisions.
If properly used, GRACE’s data could help people react to changing water patterns. For example, information about snow packs on mountains that will later melt could prove valuable to farmers.
“This is actually happening in Lake Chadï¿½ in Africa, Matt Rodell, a hydrologist at the NASA Goddard Space Flight Center, said. ï¿½… They can have a prediction based on GRACE a month or two or three in advance.”
Earlier this year, GRACE showed Greenland’s massive ice sheet is melting much quicker than estimated and that the Antarctic ice sheet is shrinking significantly. Many scientists are more concerned about those ice melting trends, in which they say global warming plays a significant role.
The University of Texas Center for Space Research has overall mission responsibility for GRACE. NASA’s Jet Propulsion Laboratory developed the satellites, which were launched by DLR. GeoForschungsZentrum in Germany operates the mission. For information, see Internet site www.csr.utexas.edu/grace.