Sikkim embarks on critical GLOF risk assessment of six high-risk glacial lakes, excludes Gurudongmar

A comprehensive expedition to assess the susceptibility of six high-risk glacial lakes in Sikkim was flagged off on Saturday by Lachen Mangan legislator Samdup Lepcha. The 15-day expedition, running from August 31 to September 14, aims to evaluate the glacial lakes of Tenchungkha, Khangchung Chho, Lachen Khangtse, Lachung Khangtse, La Tsho, and Shako Chho, which pose significant risks due to their precarious locations and environmental conditions.

Originally, the expedition was set to include the Gurudongmar lakes (A, B, and C), known for their combined volume of 178 million cubic meters. However, due to the sacred status of these lakes and local opposition, the assessment was put on hold.

The six targeted lakes, located at an average altitude of 5,200 meters in northeastern Sikkim near the China border, are in a trans-Himalayan region characterized by cold desert ecosystems. This area lies behind the Khangchengyao massif and is part of the southern Tibetan plateau. Each of these lakes presents unique risks, such as unstable moraine dams, avalanche-prone sites, and potential ice falls.

Tenchungkha Lake (4,800 meters): Spans 14 hectares with 5 million cubic meters in volume. It has a stable moraine dam but is susceptible to slope failures.

Khangchung Lake (5,320 meters): The largest lake, covering 183 hectares with 106 million cubic meters in volume, is rapidly expanding and at risk of massive ice calving.

Lachen Khangtse Lake (5,212 meters): Spans 69 hectares with 34 million cubic meters in volume, featuring a vulnerable moraine dam and no natural outlet.

Lachung Khangtse Lake (5,090 meters): Covers 26 hectares with 11 million cubic meters in volume, with high avalanche risks.

La Chho Lake (5,039 meters): Another 26-hectare lake with 11 million cubic meters in volume, considered relatively safer due to its natural outlet and lack of avalanche sites.

Sakho Lake (4,990 meters): Spans 58 hectares with 27 million cubic meters in volume, presenting threats from ice falls, avalanches, and an unstable moraine dam.

These lakes are part of the Chhombo Chu River watershed, which feeds into the Teesta River, originating from the Khangchung Chho glacier. This region also hosts Sikkim’s only brackish water lake, Gyam Tsona, a remnant of the prehistoric Tethys Sea.

The expedition is a collaborative effort involving 33 officials from six state departments, two central government agencies (GSI, CWC), the National Disaster Management Authority (NDMA), Sikkim State Disaster Management Authority (SSDMA), Sikkim University, and the Lachen Dzumsa (local self-government). The Indian Army's 27 Mountain Division and the Indo-Tibetan Border Police (ITBP) are providing critical ground support, including medical assistance.

Led by Sandeep Tambe, Secretary of the Science and Technology Department, the team will conduct various field studies. These include bathymetric investigations to determine the lakes' physical dimensions, geophysical assessments of the moraine dams, and slope stability assessments to understand potential hazards. Advanced techniques such as UAV/drone-based 3D terrain mapping and electrical resistivity tomography (ERT) will be employed to build high-resolution models and evaluate sub-surface geology.

Secretary Dicky Yangzom of the Mines and Geology Department will lead efforts to study the geological characteristics of the lakes' catchment areas, focusing on slope materials, lithology, and fault lines. Sikkim University will contribute by analyzing sediment composition, vegetation types, and permafrost conditions in the moraine complexes.

This extensive study aims to provide a detailed understanding of the risks associated with these glacial lakes, offering critical insights into potential Glacial Lake Outburst Flood (GLOF) scenarios and helping to mitigate future disasters.