The terrestrial water budget is the difference between receiving precipitation (P) and outgoing evapotranspiration and discharge (D) fluxes at the earth's surface. Recent and continuing satellite missions and constellations have measured these components separately or together at various spatiotemporal resolutions. Realistic depictions of complicated hydrologic feedback loops and correct representations of the terrestrial water budget are critical for monitoring changing water cycle features and understanding land–atmosphere interactions and extremes such as floods. This chapter discusses various radar remote sensing techniques that aid in monitoring terrestrial water budget elements such as precipitation, soil moisture, and surface water levels. This information is highlighted in three main case studies. The first case study pertains to monitoring precipitation from remote sensing using the Integrated Multisatellite Retrievals product of Global Precipitation Measurement constellation satellites. The second case study discusses estimation techniques to monitor soil moisture and downscaling for regional hydrologic studies at a fine spatial resolution. The third section elucidates the remote sensing to monitor surface water levels from radar remote sensing.
J. Indu, Akhilesh S. Nair, Ankita Pradhan, Rohit Mangla, Sooraj Krishnan, Kaushlendra Verma, Vinayak Huggannavar; Radar Remote Sensing, 2022, Pages 123-148,