Résumé
NASA and the German Space Agency (DLR) launched the GRACE satellite mission in 2002. GRACE provides accurate monthly solutions for Earth's global gravity field. Differences between solutions provide information about monthly variations in Earth's mass distribution. The results can be used to monitor changes in the total volume of water stored in regions with scales of a few hundred kilometres and larger. Total water volume includes contributions from groundwater, soil moisture, surface water, and snow. If soil moisture and surface water+snow contributions are subtracted, using observations or model output, the residuals provide groundwater variability.