If you live out West, you've likely noticed that things have been pretty dry lately. What you probably haven't noticed is that the ground beneath your feet is also a little bit higher in elevation -- an average of 4 millimeters higher, to be exact.
It may be hard to believe, but new research using data from hundreds of different GPS stations shows it to be true: The current drought in the American West is so bad that the loss of water weight has actually caused the land to rise.
Moreover, scientists behind the study found the biggest uplift took place in California's Sierra Nevada, at the nexus of the current record-breaking drought. There, the earth rose by up to 15 millimeters -- about as high as a stack of 10 pennies.
"It looks there as if they've lost maybe a foot and a half of water in those places relative to their average level before the drought took hold," said co-author Daniel Cayan, a climatologist with the Scripps Institution of Oceanography at the University of California, San Diego, and the U.S. Geological Survey.
The good news, at least from a scientific standpoint, is that the research represents a new way of showing exactly how much water is (or isn't) spread across a landscape, according to Roland Bürgmann, a professor at the University of California, Berkeley's Department of Earth and Planetary Science who was not involved in the study.
"This really shows the great potential of using these geodetic measurements of the flexing Earth's crust to address our water problems at this large scale," Bürgmann said in an email. Bürgmann and Cayan are among a growing group of researchers learning that surface and near-surface water supplies have an important influence on the Earth's crust; Bürgmann co-authored a similar study this spring demonstrating that intensive water pumping in California's San Joaquin Valley is causing the nearby mountains to bulge upward (ClimateWire, May 15).
"As opposed to other data used to measure water storage (snow depth, rain, stream and lake level gauges, soil moisture, and groundwater levels), these measurements reflect the sum of all water added or taken away," Bürgmann added.
Wanted: 62 trillion gallons of H2O
Given this new way of accounting for water loss, to what extent is the U.S. West in the red? The new research states that as of March, the water deficit over the West was equal to 240 gigatons, or 62 trillion gallons of water.
"For perspective, this deficit is equivalent to a uniform 10 cm (3.94 inch) layer of water over the entire [western U.S.] and is the magnitude of the current annual mass loss from the Greenland Ice Sheet," states the study, which was published yesterday in Science.
The scientists came to this conclusion using 772 GPS stations located across the 11 Western states, from the Rocky Mountains to the coast. Traditionally used to collect data related to the Earth's tectonic plates, these sensitive instruments measure even the tiniest movements, so much so that the researchers had to exclude stations near where a great deal of groundwater is being extracted by farmers in California's Central Valley.
A significant percentage of the West has been in drought since 2012, U.S. Drought Monitor data show, but the researchers didn't see evidence for widespread uplift until about March 2013, where it was mostly concentrated in the Pacific Northwest and Northern California.
Weather systems carrying rain and snow continued to avoid the region, however, and one year later, "the uplift had dramatically increased in California and was widespread across the entire [western U.S.]," the study states.
Drought drags on across the West
The entirety of California has been in drought since February, and today, close to 60 percent of the state falls under the Drought Monitor's most severe drought category.
Also, well over half of Nevada falls under the monitor's "extreme" drought category, and Oregon's current dry conditions are helping to spur an exceptionally high number of wildfires this summer. Arizona, New Mexico, Utah and Idaho are close to entirely blanketed in drought, as well as significant portions of Washington and Colorado.
The most arid parts of the United States aren't where the uplift is most significant, however. Rather, land is rising the most in coastal or mountainous regions, because these wet climates have experienced the biggest precipitation losses relative to the long-term average, Cayan said.
Cayan also explained that although there have been "intriguing studies" suggesting the current drought may be linked to global warming, "it's difficult to attribute this particular dry spell to climate change," he said. "Pretty severe and extended droughts are really part of the climate landscape in the West and in particular in California."
But, he added, the new way of measuring declines in water stocks could help future researchers better understand climate change's impact on hydrology across large regions of the Earth's surface.
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