Satellites Show Shrinking Aquifers in Drought-Stricken Areas

Albuquerque District’s Rio Grande coordinator, measures the water level in the Rio Grande with a calibrated survey rod. Image: Flickr/U.S. Army Corps of Engineers

The southern half of the U.S. has been rapidly depleting its groundwater over the last decade, according to new scientific research

In New Mexico, the Rio Grande is trickling through Albuquerque at only a quarter of its normal flow. The parched range and pastureland in the southwest part of the state are all rated in poor condition by the Department of Agriculture.

According to the U.S. Drought Monitor published Thursday, 45 percent of the state is suffering from “exceptional” drought — the worst in the nation. Similar conditions exist across much of the southern Great Plains.

In times like these, when rivers and irrigation canals run dry and the rain fails to fall, farmers and ranchers turn to groundwater, stored beneath the surface of the land, to wet their crops and pastures.

And as persistent drought has become almost a way of life for much of the agricultural land in the U.S., the straw of agriculture is sipping up more and more of the underground water stash.

While some regions have left drought’s clutches for the time being, overall it has been a while since Mother Nature has come around with the rain or snowfall needed for a full refill.

This has left a swath of regions across the southern half of the United States, stretching from West Virginia to California, with significant groundwater depletion since 2003, according to a paper published last week in the journal Science.

A worldwide problem

Scientists and observers of groundwater can see this nationwide change in part because of a satellite program called the NASA Gravity Recovery and Climate Experiment (GRACE), a fascinating effort that is able to measure the changes in water underneath the surface of the land.

In the paper, authors Jay Famiglietti, director of the UC Center for Hydrologic Modeling at the University of California, Irvine, and Matthew Rodell, chief of the Hydrological Sciences Laboratory at the NASA Goddard Space Flight Center, look back at some of the GRACE program’s achievements and call for continued investment in the program to improve management of groundwater resources in the United States and worldwide.

“[There is a] very dire situation that we face right now in the United States that, frankly, I don’t think many people recognize,” Famiglietti said. “I’m talking about the very rapid rates of groundwater depletion.”

In Famiglietti’s paper, there is a colored map of the United States, all blues, greens, yellows and reds. Across the southern section, concentrated red pixels note where total water loss is greater than gain, from 2003 to 2013.

There are a lot of them.

Although on a local level, some water managers may know their groundwater or aquifer is being depleted, Famiglietti highlighted the unique ability of the GRACE satellite to see what is happening with groundwater nationally and even worldwide.

The researcher is working on a global map of groundwater depletion and said that what he sees in America fits with worldwide trends, where arid and semiarid regions are losing groundwater, while more northern latitudes and the tropics are getting wetter.

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