Quantitative Analysis of the Spatiotemporal Evolution of Poyang Lake Basin From 1987 to 2023

Lakes serve as sensitive indicators of climate variability and anthropogenic disturbances. As China's largest freshwater lake, Poyang Lake plays a vital role in regional ecosystems, biodiversity and hydrological connectivity with the Yangtze River. This study developed an automated workflow to extract monthly surface water extents from 1987 to 2023 using Landsat imagery, combining the NDWI index with OTSU thresholding. The average monthly water area over the 37 years was 2421.3 km 2 , peaking at 4261.0 km 2 in July 2016 and reaching a minimum of 1084.6 km 2 in October 2022. A slight decreasing trend was observed (−2.76 km 2 /year), with strong seasonal variation: summer water area was more than double that of winter. Over time, spring and autumn exhibited consistent declines, while the summer area rebounded post‐2013. From a hydrological regime perspective, low‐flow water area increased by 17.7% after 2003, primarily expanding towards the southwest region, while high‐flow periods saw a 7.6% decrease, contrasting towards the centre. This suggests a shift in lake–river interaction, primarily influenced by the operation of the Three Gorges Dam, alongside the effects of other anthropogenic activities and climate anomalies. Spatially, permanent water bodies (inundation frequency > 75%) are concentrated in inflow channels, the central lake and artificially regulated disc‐shaped lakes. Seasonal water bodies (25%–75%) dominate the lake area, while temporary water (< 25%) is mainly found in flood‐prone zones. The constructed dataset effectively captures major hydrological events such as the 1998 and 2016 floods and the 2011 and 2022 droughts. Overall, this long‐term water area series provides new insights into the combined effects of climate anomalies and human regulation, supporting regional water management and disaster mitigation under increasing hydrological variability.