Major hydrologic shifts observed by NASA


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Researchers found that drier areas, like this drought-stricken field in Texas, are getting drier in a recent study. (U.S. Department of Agriculture/flickr)

Jenna Ladd | May 18, 2018

A recent study by NASA, the first of its kind, found that significant amounts of water are shifting around Earth’s surface.

Scientists used data from the Gravity Recovery and Climate Experiment (GRACE), two satellites, to track gravitational changes made by hydrologic shifts in 34 regions around the world. From 2002 through 2016, they paired this information with satellite precipitation data, NASA/U.S. Geological Survey Landsat imagery, irrigation maps, and public reports of human activities related to agriculture, mining and reservoir operations.

In short, researchers found that wetter areas are getting wetter and drier areas are getting drier. Jay Famiglietti of NASA’s Jet Propulsion Laboratory is one of the study’s authors. He explains, “We see a distinctive pattern of the wet land areas of the world getting wetter – those are the high latitudes and the tropics – and the dry areas in between getting dryer. Embedded within the dry areas we see multiple hotspots resulting from groundwater depletion.”

Scientists point to a couple of things to explain freshwater depletion in areas that are getting drier. In Saudi Arabia and many other parts of the world, for example, ground water has been depleted for agricultural purposes. The study also found that groundwater availability changes with periods of drought. From 2007 through 2015, southwestern California lost enough freshwater to fill 400,000 Olympic size swimming pools because the region saw less precipitation and snowpack during that time and had to rely on groundwater more heavily.

Freshwater loss in many regions was attributed to global warming that caused glaciers and ice sheets to melt away. However, Famiglietti said that much more research is needed to determine whether climate change caused the other hydrologic shifts.

GRACE Follow-On, GRACE’s successor, will continue to monitor the movement on water on Earth and is set to launch on May 22nd from Vandenberg Air Force Base California.

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