INTEGRATING GRACE SATELLITE DATA AND GROUND-BASED MONITORING AND MODELING TO ASSESS WATER STORAGE CHANGES IN U.S. AQUIFERS

GRACE satellite data have been extremely valuable in highlighting water storage changes in response to climate and human water use; however, the data are vertically integrated from the land surface to depth. Disaggregating the change in total water storage attributed to changes in surface water, soil moisture, or groundwater, requires additional data from models or monitoring to interpret the GRACE data. Traditionally, ground-based monitoring and regional modeling have been used to assess groundwater storage changes in U.S. aquifers; however, uncertainties in storage coefficients and modeling impact results. Integrating GRACE and ground-based data should advance our understanding of water storage changes with modeling and monitoring used to interpret GRACE water storage changes and GRACE data constraining regional models and monitoring results. We evaluated GRACE total water storage anomalies for major aquifers in the U.S. for 2003 – 2017 and used regional models and groundwater monitoring data to interpret the GRACE data. Results from GRACE data show large interannual variability in total water storage, particularly in the Central Valley, Arizona Alluvial Basins, and High Plains regions in response to wet and dry climate cycles. In contrast, regional water storage changes in more humid regions are much lower, such as the Columbia Basin and the Mississippi aquifer system. Calculated groundwater storage from GRACE data by subtracting other component storages from global models compare favorably with regional modeling and groundwater monitoring data in most basins. Discrepancies between GRACE and ground-based data in some basins, particularly the Mississippi Embayment Regional Aquifer System, provide valuable insights for improving our understanding of these systems. Water storage changes in response to wet and dry climate cycles are amplified (e.g. Central Valley and High Plains) or damped by human intervention. Integration of satellite and ground-based data advances our understanding of water storage changes in these basins.