Groundwater storage trends around the United States as measured by the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) satellites between 2003 and 2012. GRACE data show water losses in major U.S. agricultural regions such as (1) California's Central Valley (-1.5 ± 0.1 centimeters, or -0.59 ± 0.04 inches, per year) and (2) the Southern High Plains Aquifer (-2.5 ± 0.2 centimeters, or -0.98 ± 0.08 inches, per year), caused by overreliance on groundwater to supply irrigation water. Regions where groundwater is being depleted as a result of prolonged drought include (3) Houston (-2.3 ± 0.6 centimeters, or -0.9 inches, per year), (4) Alabama (-2.1 ± 0.8 centimeters, or -0.83 inches, per year) and (5) the Mid-Atlantic (-1.8 ± 0.6 centimeters, or -0.71 inches, per year). Water storage is increasing in (6), the flood-prone Upper Missouri River basin (2.5 ± 0.2 centimeters, or 0.98 inches, per year).
The graphs surrounding the main image are monthly time series of GRACE-derived anomalies of total water storage (in centimeter-equivalent water height) for the points annotated (1) - (6). Monthly data are displayed as darker blue lines. Trend lines (in centimeters per year-1), in red, have been added to each time series plot. Monthly errors are shown as light blue shading. Monthly GRACE data were smoothed spatially using a 200-kilometer (124-mile) Gaussian averaging kernel. All time series were smoothed using a low-pass filtering technique to remove signal with periods shorter than four months.
Data from UTCSR Release-05 and prepared by Caroline de Linage, UC Irvine.
From J. S. Famiglietti and M. Rodell, Water in the Balance, Science, 340, 1300 (2013). Figure appears as Figure S1 in Supplementary Online Materials.
Grace is a collaborative endeavor involving the Center for Space Research at the University of Texas, Austin; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the German Space Agency and Germany's National Research Center for Geosciences, Potsdam.