Zeenews Bureau
Washington: Groundwater levels in northern India have been declining by as much as one foot per year over the past decade and the loss is almost entirely due to human activity, results from NASA`s gravity satellites showed.
“More than 26 cubic miles of groundwater disappeared from aquifers in areas of Haryana, Punjab, Rajasthan and the nation`s capitol territory of Delhi, between 2002 and 2008. This is enough water to fill Lake Mead, the largest manmade reservoir in the United States, three times,” said a release of NASA.
The research was published in the journal Nature.
“A team of hydrologists led by Matt Rodell of NASA`s Goddard Space Flight Centre in Greenbelt, Md., found that northern India`s underground water supply is being pumped and consumed by human activities, such as irrigating cropland, and is draining aquifers faster than natural processes can replenish them,” the release observed.
Analysing data provided by the Ministry of Water Resources, researchers suggested groundwater use across India was exceeding natural replenishment, but the regional rate of depletion was unknown.
"The region has become dependent on irrigation to maximize agricultural productivity. If measures are not taken to ensure sustainable groundwater usage, the consequences for the 114 million residents of the region may include a collapse of agricultural output and severe shortages of potable water," Rodell added.
The finding is based on data from NASA`s Gravity Recovery and Climate Experiment (GRACE), a pair of satellites that sense changes in Earth`s gravity field and associated mass distribution, including water masses stored above or below Earth`s surface.
Changes in underground water masses affect gravity enough to provide a signal that can be measured by the GRACE spacecraft. After accounting for other mass variations, such changes in gravity are translated into an equivalent change in water.
Researchers examined data and models of soil moisture, lake and reservoir storage, vegetation and glaciers in the nearby Himalayas in order to confirm that the apparent groundwater trend was real. The loss is particularly alarming because it occurred when there were no unusual trends in rainfall. In fact, rainfall was slightly above normal for the period. The only influence they couldn`t rule out was human.
"For the first time, we can observe water use on land with no additional ground-based data collection," said co-author James Famiglietti of the University of California, Irvine. "This is critical because in many developing countries, where hydrological data are both sparse and hard to access, space-based methods provide perhaps the only opportunity to assess changes in fresh water availability across large regions."
GRACE is a partnership between NASA and the German Aerospace Centre, DLR. The University of Texas Centre for Space Research in Austin has overall GRACE mission responsibility. GRACE was launched in 2002.
