Monitoring Groundwater Depletion Due to Drought using Satellite Gravimetry: A Review

Groundwater plays a vital role in the global water cycle as a source of water for human use in daily life. The problem of groundwater depletion attracts researchers to understand the phenomenon of terrestrial water storage (TWS) and the primary technique used to monitor changes in groundwater mass in the subsurface. Accurate quantification is subtle due to the weakness of gravity measurement methods, which cover a wide range with high precision. A global evaluation of improvements in groundwater storage used a calculation tool that may involve temporal differences in TWS. The Gravity Recovery and Climate Experiment (GRACE) and the GRACE Follow-On (GRACE-FO) satellite missions were able to monitor changes in water mass in the basin and calculate changes in water levels by measuring gravity variations and quantifying groundwater tables at 1-micron precision. This paper aims to discuss GRACE, GRACE-FO and hydrological variables in the monitoring of groundwater depletion during the drought season. This paper presents an estimation technique using satellite gravimetry and hydrological methods, as well as a study of several case studies in central Amazon (Brazil), Murray-Darling (Australia) and Mongolia Basin. Previous observations, including TWS-hydrological variables, trends in groundwater depletion and drought intensity, have been discussed as a vital outcome of the paper as a whole.