Large-Scale Terrestrial Water Storage Changes Sensed by Geodesy

In this chapter, we review the applications of different geodetic techniques (GRACE, GNSS, and InSAR) to observe and infer spatio-temporal terrestrial water resource variations. We focus on the changing gravity and shape (deformation) of the Earth caused by large-scale freshwater re-distribution. We discuss the two physical models of surface deformation due to water movement, elastic loading deformation by surface water mass change, and the porous response to groundwater variations. Finally, we provide our perspective on how improvements in geodetic techniques can better monitor freshwater resources in the future. We highlight technical and scientific challenges that need to be addressed by future hydrogeodesy studies.