 The Gravity Recovery and Climate Experiment, GRACE, satellite mission provided temporal variations of terrestrial water storage, TWS, at a spatial resolution of a few hundred kilometers from March 2002 to June 2017. This dataset is widely used to quantify inter-annual variations of ground water storage in the world's major aquifers and revealed significant depletion over large regions such as the Middle East and North China Plain aquifer. GRACE-based groundwater changes can also be used to estimate parameters such as specific yield and define indices of depletion and stress. However, issues related to the use of GRACE-based TWS include its accuracy and limitations in areas with complex topography or high levels of precipitation. This article was authored by Frederick Frappert and Guillaume Vermillion.