Using satellite data, UC Irvine and NASA hydrologists have found that groundwater beneath northern India has been receding by as much as 1 foot per year over the past decade – and they believe human consumption is almost entirely to blame.
More than 109 cubic kilometers (26 cubic miles) of groundwater disappeared from the region's aquifers between 2002 and 2008 – double the capacity of India's largest surface-water reservoir, the Upper Wainganga, and triple that of Lake Mead, the largest manmade reservoir in the U.S.
People are pumping northern India's underground water, mostly to irrigate cropland, faster than natural processes can replenish it, said Jay Famiglietti and Isabella Velicogna, UCI Earth system scientists, and Matt Rodell of NASA's Goddard Space Flight Center.
"If measures are not soon taken to ensure sustainable groundwater usage, consequences for the 114 million residents of the region may include a collapse of agricultural output, severe shortages of potable water, conflict and suffering," said Rodell, lead author of the study and former doctoral student of Famiglietti's at the University of Texas at Austin.
Study results will be published online Aug. 12 in the journal Nature.
Groundwater comes from the percolation of precipitation and other surface waters down through Earth's soil and rock, accumulating in aquifers – cavities and layers of porous rock, gravel, sand or clay. In some subterranean reservoirs, the water may be thousands to millions of years old; in others, water levels decline and rise again naturally each year.
Groundwater levels do not respond to changes in weather as rapidly as lakes, streams and rivers do. So when groundwater is pumped for irrigation or other uses, restoration of original levels can take months or years.
"Groundwater mining – that is when withdrawals exceed replenishment rates – is a rapidly growing problem in many of the world's large aquifers," Famiglietti said. "Since groundwater provides nearly 80 percent of the water required for irrigated agriculture, diminishing groundwater reserves pose a serious threat to global food security."
Data provided by India's Ministry of Water Resources had suggested that groundwater use across the nation was exceeding natural replenishment, but the regional rate of depletion had been unknown.
In the new study, the hydrologists analyzed six years of monthly data for northern India from twin satellites called GRACE – NASA's Gravity Recovery and Climate Experiment – to produce a chronology of underground water storage changes.
GRACE detects differences in gravity brought about by fluctuations in water mass, including water below the Earth's surface. As the satellites orbit 300 miles above Earth, their positions change – relative to each other – in response to variations in the pull of gravity. They fly about 137 miles apart, and microwave ranging systems measure every microscopic variance in the distance between the two.
"With GRACE, we can monitor water storage changes everywhere in the world from our desk," said Velicogna, also with NASA's Jet Propulsion Laboratory. "The satellites allow us to observe how water storage evolves from one month to the next in critical areas of the world."
Groundwater loss in northern India is particularly alarming because there were no unusual trends in rainfall – in fact, it was slightly above normal during the study period. The researchers also examined data on soil moisture, lake and surface reservoir storage, vegetation and glaciers in the nearby Himalayas to confirm that the apparent groundwater trend was real. 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," Famiglietti said. "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 freshwater availability across large regions."
About GRACE: The Gravity Recovery and Climate Experiment is a partnership between NASA and the German Aerospace Center. The University of Texas Center for Space Research, Austin, has overall mission responsibility. NASA's Jet Propulsion Laboratory developed the twin satellites. The German Aerospace Center provided the launch, and GeoForschungsZentrum Potsdam, Germany, operates GRACE.
About the University of California, Irvine: UCI is a top-ranked university dedicated to research, scholarship and community service. Founded in 1965, UCI is among the fastest-growing University of California campuses, with more than 27,000 undergraduate and graduate students, 1,100 faculty and 9,200 staff. The top employer in dynamic Orange County, UCI contributes an annual economic impact of $4.2 billion. For more UCI news, visit www.today.uci.edu.
News Radio: UCI maintains on campus an ISDN line for conducting interviews with its faculty and experts. Use of this line is available for a fee to radio news programs/stations that wish to interview UCI faculty and experts. Use of the ISDN line is subject to availability and approval by the university.
Jennifer Fitzenberger | EurekAlert!
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy