Water inundation frequency reveals long-term hydrological dynamics and functional wetland zonation in Dongting Lake

Dongting Lake is a typical floodplain wetland ecosystem in the middle reaches of the Yangtze River, where long-term inundation regimes are fundamental to wetland functioning and ecological security. However, the potential of long-term inundation indicators to support functional wetland zonation remains insufficiently explored. Using long-term Landsat observations (2005–2024) processed on Google Earth Engine, water inundation frequency (WIF) was employed as an ecological indicator to characterize long-term inundation regimes and support WIF-based wetland zonation. Based on inundation gradients, wetlands were classified into four categories, including permanent water, seasonal floodplains, intermittent wetlands, and high-elevation floodplains, to investigate their spatiotemporal dynamics. The results show that: (1) the WIF product achieved high accuracy, with strong consistency with Sentinel-2 derived water extent during 2018–2022 ( R 2 = 0.92, RMSE = 10.08%), and high agreement with the JRC Global Surface Water dataset ( R 2 = 0.94); (2) WIF exhibited pronounced spatial heterogeneity, with higher inundation frequencies in East Dongting Lake and deep-water areas of South Dongting Lake, while low and medium-frequency zones were mainly distributed in West Dongting Lake and surrounding shoal regions; (3) wetland types exhibited considerable interannual variability across different hydrological conditions; (4) seasonal wetlands were mainly distributed in lakeshore zones and river–lake transition areas, and their dynamics were associated with regional precipitation variability. These findings demonstrate that WIF effectively characterizes long-term hydrological dynamics in Dongting Lake wetlands and provides scientific support for wetland conservation and ecological management.