Spatiotemporal variation in water area and the driving mechanism of Tonle Sap Lake from 2000 to 2025

Tonle Sap Lake is a seasonal floodplain lake in the Mekong River Basin and its hydrological dynamics are crucial to the ecological protection and water resource regulation of the basin. Aiming at the deficiencies of existing studies in long-term continuous monitoring, fine characterization in monthly scale, and quantitative analysis of combined driving effects of natural and human factors, we integrated multi-source remote sensing data (MODIS, Landsat, and Sentinel-1/2) and reconstructed the time series in monthly water area from 2000 to 2025 based on the Google Earth Engine (GEE) platform. By combining STL decomposition, Mann-Kendall test, inundation frequency analysis, and shoreline advance-retreat analysis, the spatiotemporal evolution characteristics of the lake, and the driving mechanisms were scrutinized systematically. Results show that the TSL presents typical seasonal fluctuations driven by monsoons annually and an clear persistent shrinking trend interannually. The shrinkage is concentrated in the peripheral floodplain, and the core water area stays stable. Precipitation dominates the intra-annual rhythm and interannual fluctuations, while upstream reservoir regulation, agricultural expansion, and rising temperature serve jointly as the dominant driving forces for the long-term shrinkage, with the superimposed amplification effect in extreme drought years. This study improved the remote sensing monitoring paradigm for hydrological processes of seasonal lakes in cross-border international basins, clarified the synergistic driving mechanism of climate and human activities, and provided scientific support for the coordinated management of the Mekong River water resources, the ecological protection of Tonle Sap Lake, and the sustainable utilization of floodplain areas.