Automated mapping and multi-decadal changes in glacial lakes in the Upper Indus Sub-Basin, Western Himalaya, using Google Earth Engine

The Western Himalayan Glacial lakes are undergoing rapid transformation as a result of intensified glacier retreat driven by changing climatic conditions, increasing the likelihood of glacial lake outburst floods (GLOFs). This study conducts an automated, multi-decadal analysis of glacial lakes in the Upper Indus Sub-Basin using Landsat imagery spanning 1990 and 2025, processed within the Google Earth Engine (GEE) platform. A Modified Normalized Difference Water Index (MNDWI), integrated with topographic constraints and morphological filtering, was employed for accurate lake extraction, followed by manual refinement. Results reveal a substantial increase in glacial lake number from 255 in 1990 to 775 in 2025, and the overall lake area increased from 34.81 to 37.72 km 2 , which indicates a gradual but consistent growth (0.083 km 2 ·a⁻ 1 ). The expansion is primarily driven by the rapid formation of small lakes (< 1 km 2 ), whereas larger lakes remain limited in number but contribute significantly to total area. Elevation analysis shows that most lakes are concentrated between 4000 and 5000 m a.s.l., which highlights strong altitudinal control on lake development. Additionally, 520 new glacial lakes were identified during the study period, which reflects persistent hydrological stability alongside dynamic lake formation. Hazard assessment based on lake characteristics, glacier proximity, expansion rate, and topographic conditions indicates increasing susceptibility of several lakes to GLOF events. The observed trends are strongly linked to regional warming and enhanced glacier melt. This study suggests the effectiveness of GEE-based approaches for large-scale cryospheric monitoring and provides critical insights for hazard assessment and water resource management in the Upper Indus Sub-Basin.