Satellite-Based River Discharge Estimation and Flood Forecasting

As a vital component of the terrestrial water cycle, river discharge integrates several physical and biogeochemical processes for sustaining ecosystems, influencing fluvial processes and related global change. Regular water level and flow measurements are crucial for effective water management, as they identify potential water scarcity issues or flood hazards. Conventionally, networks of in-situ gauge stations regularly monitored the river's water level and flow rate. However, due to numerous technical, political, and economic challenges, integrated networks of such monitoring stations are on a decline in India, as well as globally.

Due to its extensive global coverage, satellite-based monitoring provides a viable alternative to surface water monitoring. Satellite altimetry missions including ERS-1 (1991), Topex/Poseidon (1992), ERS-2 (1995), Jason-1 (2001), ENVISAT (2002), Jason-2 (2008), SARAL (2013), Jason-3 (2016), Sentinel-3A (2016), Sentinel-3B (2018) have provided remotely derived estimates of water surface elevation over the globe for the past three decades. Since river discharge cannot be measured directly from the satellites, various methods are employed to derive discharge estimates using remotely measured hydraulic variables, including water stage, channel width, slope, and surface water velocity. Additionally, several hydrological models based on the principles of water balance equation and energy conservation are employed with the help of in situ or remote sensing derived parameters to simulate water flow in a river channel. The Surface Water and Ocean Topography (SWOT) mission is the latest pursuit for improved river discharge monitoring. This mission is a joint initiative of NASA and CNES, launched in December 2022, designed to observe lakes, rivers, wetlands, and oceans at unprecedented resolution. The primary instrument on SWOT is an interferometric altimeter, which generates two-dimensional water surface elevation measurements. SWOT data can be utilized to compute accurate discharge estimates directly from SWOT measurements or by assimilation of SWOT data into hydrodynamic models.

My research focuses on exploring the potential of SWOT-derived river products, their role in obtaining improved river discharge, and how they can be used for flood forecasting and reservoir monitoring in Indian River Basins.