GPS: A New Way to Monitor Drought
GPS measurements of tiny uplifts in the Earth’s crust have helped scientists estimate groundwater depletion in the western United States, where drought has been severe since 2013. This novel approach to drought monitoring captures a component of the water cycle — variations in underground water levels — that scientists haven’t known much about. Although they can measure precipitation and surface water levels with relative ease, measuring groundwater levels, including those in aquifers, is more challenging. This is largely because terrestrial water storage, or TWS, is monitored at a limited number of locations. At these stations, GPS devices attached to solid rock or anchored a few meters below the soil measure displacement in the Earth’s crust caused by water loss. Adrian Borsa et al. took advantage of these GPS stations to better understand the extent of groundwater depletion from the Rockies to the Pacific Coast. They analyzed the past 11 years of daily crustal uplift estimated from regional GPS stations and used this data to map the impact of drought on local aquifers. The deficit so far in the western U.S. is 240 gigatons of water — the equivalent of a 10 centimeter layer of water across the entire region. Certain areas of California fare much worse, the researchers found, having local depletions up to five times the regional average.
Read more about this research from the 22 August 2014 issue of Science here.
[Image courtesy of Andre Basset, UNAVCO. Please click here for more information.]
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