MONITORING GROUNDWATER GLOBALLY WITH GRACE AND GRACE-FO SATELLITE OBSERVATIONS

Since 2002 the NASA/German Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow On (GRACE-FO) satellite missions have enabled global monitoring of changes in terrestrial water storage (TWS; the sum of groundwater, soil moisture, surface waters, snow, and ice). On interannual scales and excluding polar and high altitude regions, groundwater is the dominant component of TWS. Because available in situ groundwater depth records are sparse outside of a few heavily populated locations around the world, GRACE and GRACE-FO have been essential for inferring regional to global scale changes in aquifer storage associated with groundwater extraction and natural interannual variability. However, due to their coarse special (>100,000 km²) and temporal (monthly) resolutions and the vertically integrated nature of the observations, innovative approaches are necessary to derive actionable information. Here we present results from studies that have used GRACE and GRACE-FO to infer regional trends in TWS, understand its relationship with sea level rise, monitor drought and wetness conditions in near-real time, and identify and quantify the largest water cycle extremes in the data record.