Monitoring terrestrial water storage changes using GRACE/GRACE-FO satellite gravimetry, including groundwater depletion, drought monitoring, and ice mass balance.
Intensive agricultural pumping
Groundwater irrigation
Fossil aquifer mining
US Great Plains
GRACE TWS = Groundwater + Soil Moisture + Surface Water + Snow. GW is isolated by subtracting model estimates of other components (GLDAS, CLM).
~300 km spatial resolution limits detection of local depletion. Separation uncertainty from hydrological models can reach 20-30% of signal.
Gravity changes over ice sheets directly measure mass changes. Must correct for post-glacial rebound (GIA) which causes apparent mass gain.
1 Gt of ice = 0.0028 mm global sea level rise. Greenland and Antarctica together contribute ~1 mm/yr to global sea level.
Drought Severity Index derived from GRACE TWS anomalies normalized by historical variability. Provides integrated measure of total water deficit.
GRACE captures total column water storage including groundwater, providing earlier drought detection and more complete assessment than precipitation-only indices.
GRACE data assimilated into land surface models (NASA LIS) for operational drought monitoring by USDA and international agencies.