A year and a half of drought has depleted 63 trillion gallons of water across the Western United States, according to a new study that documents how the parched conditions are altering the landscape.
A study published in the journal Science found that the severe drought that has gripped the West since 2013 has actually caused much of the landmass in that part of the world to rise by an average of 0.16 inches. Some parts of California’s mountains have uplifted because the massive amount of water lost in the drought is no longer weighing down the land, causing it to rise.
The lost water is equal to a 4-inch layer of water across the United States west of the Rocky Mountains, according to the study.
Scientists came to this conclusion by studying data collected from hundreds of GPS sensors across the Western U.S., installed primarily to detect small changes in the ground due to earthquakes.
But the GPS data can also be used to show very small changes in elevation.
The situation is even worse underneath the snow-starved mountains of California, where the Earth rose up three-fifths of an inch. Groundwater is very heavy and its weight depresses the Earth’s upper crust.
“The thing that is exceptional about this drought is that it really covers the entire region” of the Western U.S. said Scripps assistant researcher Adrian Borsa, the study’s lead author. “I can’t tell you whether this is as big as earlier droughts, but I would say within the last 10 years, this is definitely an unprecedented change with this drought.”
“We can’t really tell you how it compares to previous big droughts,” because today’s technology didn’t exist; but suffice it to say that “it’s huge,” Borsa said of the water deficit.
“Groundwater is a load on the Earth’s crust,” said Klaus Jacob, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y., who is unaffiliated with the study. “A load compresses the crust elastically, hence it subsides. When you take that load away (by the drought) the crust decompresses and the surface rises. From the amount of rising, one can estimate the amount of the water deficit.”
The U.S. Drought Monitor has declared much of California to be in a state of “exceptional drought.”
According to the Western Regional Climate Center in Reno, 2013 was California’s driest in 119 years of records, and Los Angeles and other cities around the state recorded their lowest precipitation amounts for any calendar year.
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