HYDROLOGY

Looking beneath the drying surface

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Science  15 Aug 2014:
Vol. 345, Issue 6198, pp. 783
DOI: 10.1126/science.345.6198.783-g

Groundwater is being depleted in the Colorado Basin region even faster than the rapid drawdown of Lakes Powell and Mead. Castle et al. determined groundwater depletion in the American Southwest by using data from the GRACE satellites, which measure minute variations in Earth's gravity field: in this case, ones associated with water movement below the surface. Looking at 9 years of results beginning at the end of 2004, 4 years after the current drought there began, they find that groundwater use makes up a much larger fraction of basin water use than previously recognized. Its continued depletion, they conclude, may pose a serious threat to the region's ability to meet future water needs.

Geophys. Res. Lett. 10.1002/2014GL061055 (2014).

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