Monitoring long-term water storage of lakes and reservoirs in arid ungauged basin based on underwater topography derived from multi-source satellite data

Accurate underwater topography and water storage data of lakes and reservoirs are crucial for evaluating their functionality and sustainable water resources management. However, due to the scarcity of in-situ data, acquiring such information for remote lakes and reservoirs remains challenging. In this study, we derived multiple underwater elevation points of 14 lakes and reservoirs in the Tarim River Basin of China using ICESat-2 data, combined with the cubic B-spline fitting method. Subsequently, we utilized multi-temporal Sentinel-2 remote sensing data to map the underwater topography of these 14 lakes and reservoirs by inverting underwater elevation. Monthly time series of water area, levels, and storage were subsequently derived, offering a long-term perspective on the water dynamics of the 14 lakes and reservoirs from 1990 to 2021. The results indicate that, compared with the existing contour data of A.lake (Bosten Lake), the underwater elevation points exhibits high accuracy, with an R² of 0.90, a mean-absolute-error (MAE) of 0.72 m, and a root-mean-square error (RMSE) of 1.01 m. Additionally, the underwater topographic map of A.lake (Bosten Lake) demonstrates a high degree of fit, with an R² of 0.86, a MAE of 1.27 m, and an RMSE of 1.69 m. The findings of this study suggest that ICESat-2 data, combined with optical remote sensing imagery, are effective for mapping lakes and reservoirs in remote inland regions. Additionally, the storage dynamics of these 14 lakes and reservoirs between 1990 and 2021 reveal a notable interannual increase in water storage within the study area during the 2010–2012 period, whereas changes in the upper limit of reservoir storage were comparatively less significant. This study offers an effective approach for investigating the underwater topography and water storage of remote lakes and reservoirs with limited in-situ data, providing valuable reference information for characterizing these water bodies and managing water resources.