NASA report based on observations from multiple satellites tracks global hydrologic changes
India is among the hotspots where overuse of water resources has caused a sharp decline in the availability of freshwater, according to a first-of-its-kind study using an array of NASA satellite observations of the earth.
Scientists led by NASA’s Goddard Space Flight Center in the U.S. used data on human activities to map locations where the availability of freshwater is rapidly changing.
The study, published in the journal Nature, found that wetter parts of the earth’s were getting wetter and dry areas getting drier due to a variety of factors, including human water use, climate change and natural cycles.
Areas in northern and eastern India, West Asia, California and Australia are among the hotspots where overuse of water resources has caused a serious decline in the availability of freshwater, the study said.
In northern India, groundwater extraction for irrigation of wheat and rice crops has led to depletion, despite rainfall being normal throughout the period studied, the report said.
The fact that extractions already exceed recharge during normal precipitation does not bode well for the availability of groundwater during future droughts, the researchers said.
The team used 14 years of observations from the Gravity Recovery and Climate Experiment (GRACE) spacecraft mission, a joint project of NASA and the German Aerospace Center, to track global trends in freshwater in 34 regions around the world.
“This is the first time that we have used observations from multiple satellites in a thorough assessment of how freshwater availability is changing everywhere on Earth,” said Matt Rodell of NASA’s Goddard Space Flight Center. While some regions’ water supplies were found to be relatively stable, others experienced increases or decreases. “What we are witnessing is major hydrologic change,” said Jay Famiglietti of NASA’s Jet Propulsion Laboratory (JPL).
“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 drier. Embedded within the dry areas we see multiple hotspots resulting from groundwater depletion,” said Mr. Famiglietti.
He noted that while water loss in some regions, like the melting ice sheets and alpine glaciers, is clearly driven by warming climate, it will require more time and data to determine the driving forces behind other patterns of freshwater change.
Source: The Hindu