Evaluation of SWOT Vector Node Products Over Indian River Basins

The Surface Water and Ocean Topography (SWOT) mission, a collaboration between the US and the French Space agencies, aims to monitor ocean surface and inland waters continuously. The Ka-band radar interferometer onboard the satellite provides two-dimensional measurements of water surface elevations across two 50-km wide swaths. The SWOT mission is crucial for land hydrology as it offers significant improvements over past satellite altimetry missions with its high accuracy, wide spatial coverage, and high resolution. Our study comprehensively evaluates the accuracy of water level measurements from the SWOT Level 2 River Single-Pass Vector Node Data Product over five major river basins in India, namely Narmada, Godavari, Mahanadi, Cauvery, and Krishna. We assess the accuracy of SWOT data by comparing SWOT water elevation measurements with the water levels derived from the in-situ gauge datasets at corresponding dates and locations. We select 82 in-situ gauge stations, each with at least eight valid measurements, to evaluate the SWOT data by calculating the r², RMSE, and MAE parameters for each station. Across all five basins, the median r², RMSE, and MAE values at each station are 0.81, 0.43 m, and 0.33 m, respectively, showcasing the high accuracy of SWOT water elevation measurements over most observation points. Furthermore, we validate the SWOT water elevation levels against measurements from other satellite altimetry missions to observe its consistency across various observation platforms.