Abstract The high‐resolution measurements of surface water recorded by the recently launched Surface Water and Ocean Topography (SWOT) mission offers unprecedented opportunities toward accurate characterization of basin‐scale river discharge. This paper presents the first India‐centric study regarding the potential of assimilation of SWOT Water Surface Elevation (WSE) toward improved discharge modeling. WSE measurements are integrated into the CaMa‐Flood hydrodynamic model through a data assimilation system to improve modeled discharge over a case study river basin namely the Mahanadi River Basin in India. Assimilation experiments are conducted using real SWOT reach products for a period based on the availability of science phase observations and using synthetic SWOT reach products for a period of 3 years. The study introduces a novel framework for basin‐wide simulation of synthetic SWOT reach product, a new pre‐processing chain for quality control of real SWOT measurements prior to assimilation. Also presented is a reach‐grid allocator module tailored to map the SWOT reach product to the model grid for assimilation. Assimilation of real SWOT data improved modeled discharge by up to 44.07% and 25.21% over open‐loop simulations, as measured by assimilation metrics evaluated based on Nash–Sutcliffe Efficiency (NSE) and Root Mean Square Error (RMSE), respectively. Similar metrics evaluated for the synthetic SWOT based study revealed improvements of up to 52.03% (NSE‐based) and 30.74% (RMSE‐based). Results indicate consistent enhancements in modeled discharge through assimilation of SWOT measurements, with more pronounced effects toward the downstream river reaches on satellite overpass dates.
Soman et al. (2026) studied this question.