title: Groundwater depletion during drought threatens future water security of the Colorado River Basin.
abstract: Streamflow of the Colorado River Basin is the most overallocated in the world. Recent assessment indicates that demand for this renewable resource will soon outstrip supply, suggesting that limited groundwater reserves will play an increasingly important role in meeting future water needs. Here we analyze 9 years (December 2004 to November 2013) of observations from the NASA Gravity Recovery and Climate Experiment mission and find that during this period of sustained drought, groundwater accounted for 50.1 km3of the total 64.8 km3of freshwater loss. The rapid rate of depletion of groundwater storage (-5.6 ± 0.4 km3yr-1) far exceeded the rate of depletion of Lake Powell and Lake Mead. Results indicate that groundwater may comprise a far greater fraction of Basin water use than previously recognized, in particular during drought, and that its disappearance may threaten the long-term ability to meet future allocations to the seven Basin states.
authors.affiliation: UC Center for Hydrologic Modeling, University of California Irvine, California, USA ; Department of Earth System Science, University of California Irvine, California, USA.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Castle
authors.affiliation: UC Center for Hydrologic Modeling, University of California Irvine, California, USA ; Department of Earth System Science, University of California Irvine, California, USA ; NASA Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA.
authors.forename: Brian F
authors.initials: BF
authors.lastname: Thomas
authors.affiliation: UC Center for Hydrologic Modeling, University of California Irvine, California, USA ; Department of Earth System Science, University of California Irvine, California, USA ; NASA Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Reager
authors.affiliation: Hydrological Sciences Laboratory, NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Rodell
authors.affiliation: Climate and Global Dynamics Division, National Center for Atmospheric Research Boulder, Colorado, USA.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Swenson
authors.affiliation: UC Center for Hydrologic Modeling, University of California Irvine, California, USA ; Department of Earth System Science, University of California Irvine, California, USA ; NASA Jet Propulsion Laboratory, California Institute of Technology Pasadena, California, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Famiglietti
keywords: Colorado River Basin; GRACE; drought; groundwater; groundwater depletion; water management
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