Monday, August 17, 2009
Whenever I see a scientific study about water on Earth, I check to see if it involves the Gravity Recovery and Climate Experiment (GRACE).
GRACE is a NASA mission run by The University of Texas at Austin and the German Aerospace Center. Byron Tapley, professor in the Department of Aerospace Engineering and Engineering Mechanics, is GRACE’s principal investigator.
Since the start of GRACE in 2002, data it has collected have generated scores of papers about the Earth’s climate and water resources.
The latest projects with just-published results used GRACE data to show that groundwater in a large area of northern India is “being pumped and consumed by human activities — principally to irrigate cropland — faster than the aquifers can be replenished by natural processes.”
The other study was conducted by the National Geophysical Research Institute in Hyderabad, India. That paper is to be in an upcoming Geophysical Research Letters.
ScienceNews reported on both experiments.
Besides the instrument used to collect data, the NASA project has other ties to The University of Texas at Austin.Matt Rodell, hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Md., the lead author of the paper, received his Ph.D. at the university.
A co-author on the paper was James S. Famiglietti. He was a professor in Austin, where he was Rodell’s Ph.D. adviser, before going to the University of California, Irvine. The third author is Isabella Velicogna, of NASA’s Jet Propulsion Laboratory and the University of California,Irvine and another serial user of GRACE data.
Rodell and Famiglietti know GRACE well, having conducted two initial studies of its technique.
Here’s how the NASA release described what GRACE does:
The twin satellites of GRACE can sense tiny changes in Earth’s gravity field and associated mass distribution, including water masses stored above or below Earth’s surface. As the satellites orbit 300 miles above Earth’s surface, their positions change–relative to each other–in response to variations in the pull of gravity. The satellites fly roughly 137 miles apart, and microwave ranging systems measure every microscopic change in the distance between the two.
The NASA press release about the India project also quotes Bridget Scanlon, a hydrologist at the Jackson School of Geosciences at The University of Texas in Austin, talking about the impact of water shortages.
“At its core, this dilemma is an age-old cycle of human need and activity–particularly the need for irrigation to produce food,” Scanlon said. “That cycle is now overwhelming fresh water reserves all over the world. Even one region’s water problem has implications beyond its borders.”