[[VIDEO.PLAYER||Global Terrestrial Water Storage Anomaly||The gravity variations studied by GRACE were used to determine ground water storage on land masses. By comparing recent data to an average over time, scientists can generate an anomaly map to see where ground water storage has been depleted or increased. Rust colored areas show areas where ground water has decreased, and areas in blue are where ground water levels have increased. Note the significant decreases in ground water storage across most of California and all the way up the North American coast into Alaska.||/system/video_items/14_grace_world_anom.6.mp4||undefined||undefined||/system/resources/detail_files/20_grace_world_anom_print.jpg||The gravity variations studied by GRACE can be used to determine ground water storage on land masses.||Column-width||20||false||false]]

"From 2002 to 2017, NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites monitored large-scale groundwater changes all over the globe. In northwest India, the Middle East, and also close to home here in California's Central Valley aquifer, a significant fraction of the water needed to farm comes from groundwater. With GRACE-FO, like with GRACE, we have a unique tool that allows us to very accurately detect where and how much water is pumped from deep below – providing crucial data to support water management and to determine if pumping rates might be unsustainable."

Dr. Felix Landerer, GRACE-FO deputy project scientist

Groundwater is an indicator of climate variability and human impacts on the environment. Combining GRACE data with hydrologic modeling enables scientists and water managers to observe dynamic changes in groundwater over large regions or where well data are sparse. GRACE-FO will provide global measurements on seasonal and inter-annual river basin water storage changes, human influences on regional water storage changes, large-scale evapotranspiration, land-ocean mass exchange, and continental aquifer changes. GRACE data are currently being used to generate weekly drought indicators at the National Drought Mitigation Center.

Studies have found that a third of Earth’s largest groundwater basins are being rapidly depleted by human consumption, despite not having accurate data about how much water remains in them. That means significant segments of Earth’s population are consuming groundwater without knowing when it might run out, researchers found. Two studies led by the University of California, Irvine (UCI), used data from GRACE to comprehensively characterize global groundwater losses from space.

“Available physical and chemical measurements are simply insufficient,” said UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Given how quickly we are consuming the world’s groundwater reserves, we need a coordinated global effort to determine how much is left.”

California drought as seen by GRACE.
NASA GRACE data shows land in much of California's Central Valley sinking from groundwater extraction.

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