West loses 63 trillion gallons of groundwater to drought

Molly Peterson

August 21 2014

Networks of GPS systems across the Western United States have revealed geologic uplift connected to the absence of water in the landscape. Findings of a study of the data are published in the journal Science by a team from the Scripps Institute of Oceanography and the U.S. Geological Survey.COURTESY SCRIPPS/UCSD

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Researchers on Thursday reported the Western United States has lost 63 trillion gallons of groundwater since the beginning of 2013 due to the ongoing drought, causing the surface of the Earth to rise slightly.

The study from the U.S. Geological Survey and the Scripps Instituion of Oceanography was published in the journalScience.

The researchers discovered the groundwater loss and geologic uplift by using a network of GPS stations typically used to monitor seismic activity. Using the stations, researchers measured minute elevation gains and used them extrapolate the amount of groundwater lost.

Among their findings:

  • 63 trillion gallons is a lot of water: The amount of groundwater lost since the beginning of last year is enough to cover the U.S. west of the Rockies with four inches of water.
  • Water is heavy: The Earth is like a spring, and groundwater is like a weight on that spring. Remove 63 trillion gallons and the Western U.S. has rebounded an averge of 0.15 inches.
  • Mountains store a lot of groundwater. California’s mountains were depressed more than half an inch by the groundwater underneath them.
  • The weight of water can help track California’s drought. “We can home in on the Sierra Nevada mountains and critical California snowpack,” said Dan Cayan, a research meteorologist with the USGS and Scripps. The technique can work anyplace there’s a similar network of GPS sensors.