Monitoring water storage and its variations is impor-tant to understanding local hydrological processesand the global water cycle, which sustains all life onEarth. The development of satellite remote-sensingtechniques has benefited the retrieval of terrestrialwater storage and its variations, which has emerged asa new discipline. Focusing on terrestrial water storage,this chapter describes three major retrievalapproaches: the water-balance-based approach, thesurface-parameter-based approach, and the GravityRecovery and Climate Experiment (GRACE)-basedapproach. Accurate estimates of terrestrial waterstorage and its variations are still being developed.
