GDO Total Water Storage Anomaly (TWSA) (GRACE) (version 2.1.1)

The Total Water Storage (TWS) Anomaly indicator that is implemented in the Copernicus Global Drought Observatory (GDO) is used for determining the occurrence of long-term hydrological drought conditions, which arise when the TWS reaches values lower than usual. This quantity is often used as a proxy of groundwater drought. The TWS Anomaly indicator in GDO is computed as anomalies of GRACE-derived TWS data with respect to the long-term average 2002-2023 for data from 2002 to 2024 and to the long-term average 2002-2024 for data of year 2025. TWS data are produced by the Center for Space Research (CSR) at the University of Texas at Austin, as scaled by the NASA Jet Propulsion Laboratory (JPL).