GANGTOK, SEPTEMBER 4: Sikkim has identified 40 high-hazard glacial lakes across the state, with 16 classified as being at the highest risk of a potentially catastrophic Glacial Lake Outburst Flood (GLOF), officials said.
The assessment assumes added significance amid growing concerns over climate-driven changes in the Himalayas, where glaciers are retreating, new glacial lakes are forming and existing water bodies are expanding.
Of the 40 high-hazard lakes identified in Sikkim, 16 fall under Category A, indicating the highest risk, while two are in Category B and nine in Category C. The remaining 13 lakes are yet to be classified, officials said.
Glacial lakes are formed when melting glaciers create depressions that accumulate large quantities of meltwater. A sudden breach of such a lake, triggered by factors including excessive water accumulation or earthquakes, can result in a GLOF, sending destructive volumes of water downstream.
Sikkim witnessed a devastating GLOF in October 2023 that claimed at least 60 lives 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.
Speaking at a media sensitisation workshop on GLOF risk mitigation, Principal Secretary Sandeep Tambe said remote sensing and satellite imagery were being used to monitor changes in glacial lakes.
The state has designated its Department of Science and Technology as the nodal agency for GLOF hazard assessment and mitigation studies. Officials said work is being undertaken through an interdisciplinary approach involving field surveys, water-level and discharge monitoring, geophysical studies, bathymetry, flood modelling and hazard assessment.
Sikkim is also working on a dedicated GLOF Risk Mitigation Protocol, which is expected to provide a standardised scientific framework for assessing, preparing for and reducing glacial flood risks. Officials said the framework could serve as a model for other Himalayan regions.
The state government has identified Shako Chho as the most vulnerable glacial lake. A Detailed Project Report for its mitigation has been submitted to the National Disaster Management Authority, while a preliminary project report has been forwarded to the Ministry of Jal Shakti.
For the Lhonak Complex, the Central Water Commission and Sikkim Government are preparing a DPR for a proposed flood-retention structure at Dolma Sampa near Muguthang. A moraine plug wall has also been proposed at the outlet of the Gurudongmar Complex.
Officials said several lake-level lowering techniques are being examined, including siphoning, pumping, improving existing channels, constructing artificial channels, moraine cutting with safety walls and tunnelling.
The state is following a four-stage mitigation strategy involving preliminary assessment, comprehensive assessment, design of mitigation measures and execution.
Additional early-warning sensors have also been proposed across Sikkim to strengthen the state’s preparedness against GLOF threats.
The developments come days after Union Home Secretary Govind Mohan reviewed the preparedness of Himalayan States and Union Territories against GLOFs and snow avalanches, with senior officials from Jammu and Kashmir, Uttarakhand, Himachal Pradesh, Sikkim and Arunachal Pradesh, among others, participating in the meeting.
