Spatiotemporal dynamics and driving factors of surface water in the Middle and Lower Yangtze River Basin from 1986 to 2023

Study region Middle and Lower Yangtze River Basin, China. Study focus Natural and anthropogenic drivers synergistically influence the spatiotemporal characteristics of surface water in the Middle and Lower Yangtze River Basin (MLYRB). However, due to the immense challenges in processing long-term time series data, the long-term changes in surface water area (SWA) within the MLYRB remain inadequately revealed. This study utilized all available Landsat imagery, a robust water body mapping algorithm based on spectral indices and thresholds, and the Google Earth Engine (GEE) cloud computing platform to extract MLYRB SWA from 1986 to 2023 and conduct a comprehensive assessment of its dynamics. New hydrological insights for the region SWA exhibits a sustained decreasing trend (-169.75 km²/yr, p < 0.01), permanent surface water area (PSWA) maintains high stability (CV=0.07), while seasonal surface water area (SSWA) accelerates its decline (-152 km²/yr, p < 0.01). Quantitative attribution indicates that precipitation dominates water body replenishment, while vegetation expansion (ecological encroachment) significantly drives the decline in SSWA. Human interventions—particularly post-Three Gorges Reservoir impoundment—reversed the decline in downstream PSWA but accelerated SSWA contraction ( −242.04 km²/yr). This synergistic influence of natural and anthropogenic factors underscores the complexity of surface water evolution in the basin. This study provides updated information on the spatiotemporal dynamics of surface water in the MLYRB, contributing to the advancement of effective regional water resource management.