Identification and assessment of potentially dangerous glacial lakes in Uttarakhand, India

The Himalayas, often termed the Third Pole, host the largest expanse and volume of permanent ice and permafrost outside the Polar Regions. The ongoing recession of glaciers, driven by climate change, has led to the formation of new glacial lakes through the accumulation of meltwater between the retreating glacier and its frontal moraine, as well as the expansion and merging of existing lakes. This process increases the risk of glacial lake outburst floods (GLOFs), posing a significant threat to downstream communities. In Uttarakhand, India, more than a thousand glacial lakes present considerable challenges for monitoring and risk assessment. Hence, it is essential to identify and prioritize potentially dangerous glacial lakes (PDGLs) for effective risk management. Using Sentinel-2 satellite imagery, 426 glacial lakes with a surface area greater than 1,000 m² were inventoried; these lakes cover a cumulative area of ~ 3.34 × 106 m2. Based on their vulnerability to the GLOF hazard, 25 out of 426 lakes were classified as PDGLs. Lake vulnerability was assessed using a parameter-weighting approach, considering factors such as volume, expansion, dam condition, distance from settlements, and upstream and downstream conditions of the valley. These lakes were further classified into three hazard categories: six lakes in Category A (most hazardous), six lakes in Category B (moderately hazardous), and 13 lakes in Category C (least hazardous). Alaknanda and Dhauliganga Valleys contain 9 and 6 PDGLs, respectively, making them most sensitive to GLOF hazards. These findings underscore the urgent need for focused monitoring and mitigation strategies to address GLOF risks in the region.