Monitoring alpine wetland of Haizishan using Otsu method and Sentinel-1 SAR in Hengduan Mountains, China

This study focuses on delineating water extent within the alpine wetlands of Haizishan, Qinghai-Tibet Plateau, a meteorologically complex region. Situated within a 6,000 km² Quaternary ice sheet landscape with over 600 water bodies, this area offers a crucial setting to examine climate change impacts on high-altitude wetland systems. Employing Sentinel-1 SAR data and the Google Earth Engine (GEE) platform, we implemented an Improved OTSU algorithm, achieving > 95% accuracy in water surface delineation despite persistent cloud cover. Notably, wetland water extent expanded from 52.9 km² to 54.8 km² between 2015 and 2022, correlating with increased precipitation. This expansion, and its precipitation-driven nature, distinguishes these non-glacial-fed wetlands hydrologically from glacial water bodies in the broader region, particularly impacting shallower wetland areas sensitive to thermal variations.