Jonas Santos de Souza (Federal University of Pernambuco, Brazil); Mayara Silva de Oliveira (Federal University of Pernambuco, Brazil); Marielle Gosset (Institut de Recherche pour le Développement, France)

Water level monitoring is crucial for water resource management and addressing the challenges of climate change. The new Surface Water and Ocean Topography (SWOT) mission provides unprecedented spatial and temporal resolution estimates of water surface elevation (WSE) for water bodies worldwide. This study evaluated the accuracy of WSE SWOT estimates over a set of reservoirs and river reaches in the Northeast Brazil. The water bodies are located, part in the Pernambuco state and part in the São Francisco river basin, one of most important in the region. The products evaluated included L2_HR_LakeSP Prior, L2_HR_RASTER 100m and L2_HR_RiverSP Node. The products were compared with observed data from stations for the period between April/2023 and March/2025. The accuracy of the WSE SWOT values was evaluated through the Pearson correlation coefficient r, Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE). The results showed that the WSE SWOT time series obtained a good fit to the in-situ water level monitoring, with Pearson’s r correlation coefficient greater than 0.9 in most stations. On the other hand, in some cases, WSE SWOT data have difficulty to represent properly the in-situ time series. Satellite measurement errors may be due to instrumental, atmospheric, and geophysical factors. Overall, the SWOT products showed good potential for use in monitoring water elevation in the rivers and lakes selected for assessment, with good accuracy and trend detection capabilities. Better filtering of outliers and improved accuracy in river reaches with sandbars would help to increase the accuracy of the products.