NEW DELHI: The National Green Tribunal (NGT) has raised alarm over the growing threat of glacial lake expansion in the fragile Himalayan region, a consequence of accelerated glacier melt caused by climate change. The tribunal has directed the National Institute of Hydrology (NIH) to submit a comprehensive report within four weeks assessing the risks posed by these glacial lakes and suggesting mitigation strategies.
Glacial lakes form when retreating glaciers melt and their water accumulates in natural basins. While these lakes are a visible sign of a warming planet, their instability poses a deadly threat. If the natural dams containing these lakes breach, they can unleash Glacial Lake Outburst Floods (GLOFs), leading to catastrophic downstream flooding.
The tribunal’s intervention follows the devastating GLOF that occurred on October 3, 2023, when South Lhonak Lake in Sikkim burst, triggering a massive flood that washed away critical infrastructure, including a 1,200 MW hydropower dam on the Teesta River.
In its submission to the NGT, the Central Water Commission (CWC) revealed that it had conducted a risk assessment of 100 glacial lakes across the Indian Himalayan region, each spanning more than 10 hectares. The breakdown includes 42 lakes in Sikkim, 15 each in Ladakh and Jammu & Kashmir, and nine each in Uttarakhand and Arunachal Pradesh.
Of these 100 glacial lakes, 34 are reportedly expanding, 20 are shrinking, and 67 dams lie in their downstream paths—raising concerns about the vulnerability of vital infrastructure.
The CWC has developed a structured Glacial Lake Risk Index that incorporates parameters like lake size, rate of growth, slope stability, and the exposure of nearby settlements and dams. This index is expected to serve as a framework for ranking lakes based on the probability of bursting and the extent of potential damage.
The tribunal has now ordered the NIH to provide further technical inputs and submit a report with detailed recommendations. The next hearing in the matter is scheduled for October 16, where the tribunal will review the findings and plan further action.
Climate experts have long warned that rising global temperatures are accelerating the retreat of glaciers in the Himalayas, triggering the formation of numerous glacial lakes. Many of these newly formed or rapidly expanding lakes are situated precariously, held back only by weak moraine dams—natural accumulations of debris that can easily collapse under pressure.
The Sikkim disaster in 2023 and the 2021 Chamoli floods in Uttarakhand have served as grim wake-up calls. Environmentalists are urging a comprehensive review of all hydropower projects in the Himalayan states, especially those lying in the path of glacial lake outburst flood zones.
Studies have repeatedly flagged South Lhonak Lake as one of the fastest-growing and most hazardous glacial lakes in the Teesta basin. Its eventual breach and the resulting devastation were described by experts as a “disaster foretold.”
With the NGT’s renewed scrutiny, the focus has now shifted to strengthening early warning systems, upgrading dam safety protocols, and ensuring climate-resilient planning in the Himalayan region.
