Sikkim has proposed three major engineering interventions to reduce the risk from Glacial Lake Outburst Floods (GLOFs) – solar-powered pumping at Shako Chho, a flood-retention structure at Dolma Sampa in the Lhonak Valley, and a safety wall at the outlet of the Gurudongmar lake complex.
Chief Engineer Ashim Basnett said reducing the lake’s volume would reduce the potential force of water released by a future avalanche, landslide or similar event. The proposals mark a shift from assessing glacial hazards to exploring concrete measures to reduce the potential impact of a GLOF. Its terminal moraine is high but permeable, and the lake has no natural outlet. The National Disaster Management Authority (NDMA) has advised against directly disturbing the fragile moraine. A Detailed Project Report (DPR) has been prepared and submitted through the state disaster management authorities, with the proposal being examined at the Government of India level. The second proposal concerns the Lhonak Complex, comprising South Lhonak, North Lhonak and Changsang lakes.
The proposal therefore envisages initially pumping out around 8 million cubic metres of water using eight solar-powered pumps, with the possibility of lowering the lake level by about 20-40 metres. Because there is no electricity supply at the site and transporting fuel to such a high altitude would be difficult, conventional pumping is considered impractical. At Shako Chho, located at around 17,000 feet and about 12 km from Thangu on the route to Gurudongmar, the proposal is to lower the lake level through solar-powered pumping. The lake is estimated to hold around 27 million cubic metres of water. Instead of carrying out an intervention directly at the lakes, Sikkim is studying a retention structure at Dolma Sampa, around 24 km downstream near Muguthang, where the valley widens naturally.
Principal Secretary of the Science and Technology Department Sandeep Tambe said the focus was now on mitigation. “Studying glaciers is one thing, but we are mostly working towards glacial hazard mitigation,” Tambe said. “The best way to stop it is at the lake itself,” Basnett said, explaining that reducing the depth and volume could lessen the impact of a possible outburst.
