Environment

Massive groundwater depletion in U.S.

Over a 14-year period, the Colorado River basin in the U.S. has lost nearly 65 cubic km of freshwater, almost double the volume of the nation's largest reservoir, Nevada's Lake Mead.

More than three-quarters of the total — about 50 cubic km was from groundwater. The basin region has been experiencing severe drought for the past 14 years.

The loss came to light from observations by NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission satellites which track changes in mass of the Colorado River Basin which are related to changes in water amount on and below the surface. Monthly measurements of the change in water mass from December 2004 to November 2013 were made.

While the U.S. Bureau of Reclamation manages water above ground in the basin's rivers and lakes and documents its losses, pumping from underground aquifers is regulated by individual states; it is often not well documented.

The Colorado River basin supplies water to about 40 million people in seven states, as well as irrigating roughly four million acres of farmland. The Colorado River is the only major river in the southwestern United States.

“The only way for the basin to sustain its water future and continue to meet its allocation commitments is [for the government] to begin including groundwater in basin-wide water planning and management discussions as groundwater is the strategic reserve during drought,” notes Dr. Jay Famiglietti in an email to this Correspondent.

Dr. Famiglietti is Senior Water Cycle Scientist, NASA Jet Propulsion Laboratory, California Institute of Technology and professor at department of Earth System Science and Civil and Environmental Engineering, University of California, Irvine.

Is the drought linked to global warming?

“Any individual drought, like the prolonged drought in the Colorado River Basin, cannot be tied to global warming,” he said. “However, the expectation for an increasing number of these events in the future is in fact an expected outcome of global warming.”

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Printable version | Sep 24, 2020 7:03:38 PM | https://www.thehindu.com/sci-tech/energy-and-environment/massive-groundwater-depletion-in-us/article6288188.ece

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