Assessing SWOT's Measurement Capabilities in the Complex Paraná River

Abstract

Estimating water surface elevation (WSE) is crucial for understanding hydrological processes;however, many rivers remain insufficiently monitored due to the limitations of in situ gauge networks. The Surface Water and Ocean Topography (SWOT) mission, equipped with Synthetic Aperture Radar technology, enables global monitoring of WSE with high spatial resolution. In this study, the performance of the SWOT WSE estimates during the Calibration/Validation and Science mission phases was assessed in the complex Paraná River system against in situ observations using cross‐section and longitudinal profile approaches. Specifically, WSE estimates from the SWOT Level 2 high‐rate raster product (L2_HR_Raster CRID version PGC0) were compared with WSE gauge stations and pressure transducer measurements collected at six locations along the Paraná River between March 2023 and May 2024. Results showed strong agreement withobservations, yielding Root Mean Square Errors (RMSE) less than 0.21 m, coefficients of determination (R2) greater than 0.78, 1‐sigma errors lower than 0.13 m, and biases between 0.11 and 0.20 m. Complementary longitudinal analyses were conducted using Global Navigation Satellite System profiles with SWOT L2_HR_Raster and Level 2 high‐rate vector (L2_HR_RiverSP node version D) products. SWOT estimates captured the spatial variability of WSE along the different channels of the Paraná River, while derived water surface slopes (WSSs) showed RMSEs lower than 12 mm km􀀀 1. Additionally, pixel quality and riverbank interference were also analyzed, and a filtering procedure for using SWOT data in lowland rivers is proposed. The findings highlight the mission´s potential to accurately monitor WSE and WSS in large fluvial systems.