GRACE mission offers a much needed view of Earth's water supplies

Sep 14, 2012 by Holli Riebeek

The signature of drought was easy to read in the southern United States in the summer of 2011. It was in the brown, wilted crops and the bare fields. It was in the clouds of dust that rolled across the sky and in the shrinking reservoirs. It was in the fires that raced through crisp grasslands and forests, devouring homes and wilderness. It was in the oppressive heat that returned day after day.

Drought was harder to see as 2011 drew to a close. With the return of winter, rains began to fall and temperatures dropped. But the drought was still there, lingering beneath the surface. It was still apparent to hydrologists who test the wells that plunge deep into underground aquifers.

This lingering, subtle drought was also visible to a highly unusual pair of satellites.

This video is not supported by your browser at this time.
Measurements of underground water storage (aquifers)—rather than surface water (lakes, rivers, etc.)—reveal the long-term effects of drought. This map shows ground water conditions in the U.S. during the week of November 28, 2011, compared to the long-term average. A time-series animation shows the evolution of ground water from 2002 to 2012. Credit: Chris Poulsen, National Drought Mitigation Center, based on data from the GRACE science team.

In Nebraska, Brian Wardlow and colleagues at the National Drought Mitigation Center watched the drought long before and after the average citizen paid heed. Wardlow develops satellite-based products that experts use—along with more traditional —to assess the severity of drought. Looking at measurements from the satellites, Wardlow could see broad-scale changes in groundwater supplies at varying depths over large swaths of the South.

After a year without much rain, it was no surprise that the lingered below the land's surface. "Groundwater takes a long time to be depleted, but it takes a long time to be recharged as well," says Wardlow, a remote sensing specialist at the University of Nebraska–Lincoln. From experience, he expected regional groundwater supplies to be diminished. But this time he could see it in greater detail than traditional well measurements had ever provided.

GRACE mission offers a much needed view of Earth’s water supplies
The twin GRACE satellites launched on March 17, 2002, aboard a Russian rocket. Credit: NASA JPL

Observing the water buried beneath layers of soil and rock was no small thing. When the twin satellites known as the Gravity Recovery and , or GRACE, were launched in March 2002, few hydrologists believed they could see—no less measure—changes in groundwater. But at least two scientists did: Jay Famiglietti and his graduate student Matt Rodell, who were working at that time at the University of Texas at Austin (UT-Austin).cale changes in groundwater supplies at varying depths over large swaths of the South.

Now a scientist at NASA's Goddard Space Flight Center, Rodell has spent the past decade studying groundwater with GRACE and working to make those measurements useful to decision-makers. Thanks largely to Famiglietti, Rodell, and a handful of other scientists, GRACE's measurements of groundwater, ice, and oceans are now so essential that NASA is preparing to launch a follow-on mission.

Explore further: Rising anger as Nicaragua canal to break ground

add to favorites email to friend print save as pdf

Related Stories

Texas drought visible in new national groundwater maps

Nov 30, 2011

(PhysOrg.com) -- The record-breaking drought in Texas that has fueled wildfires, decimated crops and forced cattle sales has also reduced levels of groundwater in much of the state to the lowest levels seen ...

Satellite data explains vanishing India groundwater

Aug 12, 2009

(PhysOrg.com) -- 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 ...

Recommended for you

Rising anger as Nicaragua canal to break ground

4 hours ago

As a conscripted soldier during the Contra War of the 1980s, Esteban Ruiz used to flee from battles because he didn't want to have to kill anyone. But now, as the 47-year-old farmer prepares to fight for ...

Hopes, fears, doubts surround Cuba's oil future

Dec 20, 2014

One of the most prolific oil and gas basins on the planet sits just off Cuba's northwest coast, and the thaw in relations with the United States is giving rise to hopes that Cuba can now get in on the action.

New challenges for ocean acidification research

Dec 19, 2014

Over the past decade, ocean acidification has received growing recognition not only in the scientific area. Decision-makers, stakeholders, and the general public are becoming increasingly aware of "the other carbon dioxide ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.