Sikkim Identifies 40 High-Hazard Glacial Lakes, 16 at Highest Risk

Sikkim has identified 40 high-hazard glacial lakes, including 16 classified in the highest-risk category, amid growing concerns over the impact of accelerating glacier retreat across the Himalayas.

The assessment was highlighted at a media sensitisation workshop on Glacial Lake Outburst Flood (GLOF) risk mitigation held in Sikkim on Thursday. Principal Secretary Sandeep Tambe said remote sensing and satellite imagery were being used to monitor changes in glacial lakes and assess potential hazards.

Of the 40 identified lakes, 16 are in Category A, denoting the highest risk, while two are in Category B and nine in Category C. Thirteen lakes remain unclassified.

The concerns come after a flash flood near the Nepal-Tibet border on August 26, triggered by a glacial collapse. Although the incident was not classified as a GLOF, it has renewed attention on Himalayan hazards as glaciers retreat, new lakes emerge and existing water bodies expand.

Sikkim itself witnessed a devastating GLOF in October 2023, which killed at least 60 people and caused extensive damage across Mangan, Gangtok, Pakyong and Namchi districts. The disaster also destroyed the Chungthang dam, a key component of a major hydropower project.

The state government has identified Shako Chho Lake as particularly vulnerable. A Detailed Project Report has been submitted to the National Disaster Management Authority, while a preliminary project report has been sent to the Jal Shakti Ministry.

Officials are examining measures including siphoning, pumping, artificial channels, moraine cutting, tunnelling and flood-retention structures. Separate mitigation proposals have been prepared for the Lhonak Complex, Shako Chho and Gurudongmar Complex.

Sikkim is also working on what could become India’s first dedicated GLOF Risk Mitigation Protocol, designed to establish a standardised scientific framework for hazard assessment, preparedness and mitigation.

Additional early-warning sensors have also been proposed across the state as authorities seek to strengthen preparedness against future glacial hazards.