Satellite Remote Sensing of Hydrological Change

Satellites provide an increasing amount of global information and new opportunities for environmental monitoring and modelling. The value of remotely sensed data is especially relevant in the context of global hydrological modelling, an emerging field of research with applications of great societal impact. It provides important information on the status and spatio-temporal changes of water resources world-wide, which inform policies on integrated water resources management and mitigation of water-related hazards such as floods and droughts. The Chapter reviews the opportunities offered by satellites for monitoring the water cycle under human impact. We discuss the fluxes of water through rainfall, surface and groundwater runoff, evaporation, transpiration and condensation, and review the opportunities for their observation offered by satellite missions. Using the water balance equation as a basis, we discuss in detail the Gravity Recovery and Climate Experiment (GRACE) mission and a small sample of other contributing missions, such as the Surface Water Ocean Topography (SWOT), Soil Moisture and Ocean Salinity (SMOS), Soil Moisture Active Passive (SMAP), Tropical Rainfall Measuring (TRMM), Global Precipitation Measurement (GPM), Clouds and the Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS). We conclude the chapter with perspectives and requirements for the future, and we stress the need for continuous, long-term monitoring of the global water cycle from space.