Gangtok: An expedition to assess the susceptibility of glacial lakes to outburst floods (GLOF) was flagged off on Saturday by Lachen Mangan legislator Samdup Lepcha from Gangtok.
The 15-day expedition, scheduled from August 31 to September 14, will focus on six high-risk glacial lakes: Tenchungkha, Khangchung Chho, Lachen Khangtse, Lachung Khangtse, La Tsho, and Shako Chho.
Initially, the State government had planned to assess the Gurudongmar lakes (A, B, and C), which have a combined estimated volume of 178 million cubic meters. However, these plans have been postponed due to local opposition, as the lakes are considered sacred.
Gurudongmar is a sacred lake
The Pippons of Lachen and Lachung along with citizens have expressed concern over visiting these sacred lakes. Part of the reason why Gurudongmar, which is considered one of the most sacred lake was left out of the expedition, after earlier being included.
Former minister Tseten Tashi Bhutia, who serves as a convener for Sikkim Bhutia Lepcha Apex Commitee (SIBLAC) has expressed, “This GLOF expedition team should also have consisted of a member from monk body from Ecclesiastical department to guide them.
These lakes are very sacred lakes protected by the Places of Worship (Special Provisions) Act, 1991, the law passed by the Parliament of India and notified by Govt of Sikkim in 1997/98. Please recall what the Pippon of Lachen said publicly during Lhonak GLOF happened. The wrath had to be faced by them and people of Sikkim and still facing due to negligence and the blunder in the administration system. So, do not repeat the same mistake. I humbly request Ecclesiastical department to intervene in this matter”.
Bhutia asserted, “No Objection Certificate from ecclesiastical department is mandatory as per above notification even to enter the vicinity of places of worship. The GLOF expedition team didn’t mention a single word that they had the consent from ecclesiastical department”.
However, Ecclesiastical Secretary Passang D. Phempu refused to comments made by the former minister. He stressed that he remains unaware of expedition team heading to the sacred lakes.
Multi-department, multi-institution effort
The six high-risk lakes, located at an average elevation of 5,200 meters, are in the northeastern corner of Sikkim near the China border. This trans-Himalayan landscape, a cold desert ecosystem, lies behind the Khangchengyao massif and the main Himalayan range.
Tenchungkha Lake, at an elevation of 4,800 meters, spans 14 hectares and holds 5 million cubic meters of water. It has a stable moraine dam but faces threats from unstable lateral moraine prone to slope failures and potential avalanches. Khangchung Chho, the largest of the six lakes, is at 5,320 meters and covers 183 hectares with 106 million cubic meters of water.
The lake is expanding, with its glacier tongue in direct contact, posing risks of massive ice calving and avalanches. Lachen Khangtse Lake, at 5,212 meters, spans 69 hectares and holds 34 million cubic meters of water. It has no natural outlet and is threatened by a vulnerable moraine dam and hanging glaciers. Lachung Khangtse Lake, at 5,090 meters, covers 26 hectares with 11 million cubic meters of water. It faces high risks of avalanches and ice falls, with a vulnerable moraine dam and no natural outlet.
La Tsho, near Lachung Khangtse, is at 5,039 meters, covering 26 hectares with 11 million cubic meters of water. It is considered comparatively safer, with no potential avalanche sites and a natural outlet. Shako Chho, at 4,990 meters, spans 58 hectares with 27 million cubic meters of water. It lacks a natural outlet and is threatened by ice falls, potential avalanches, and a vulnerable moraine dam with limited freeboard.
These lakes are part of the Chhombo Chu River’s watershed, a tributary of the Teesta River. The expedition aims to evaluate the lakes’ physical dimensions, including volume, depth, and longitudinal profiles, through a bathymetry survey. The team will also assess the stability and risk factors of moraine dams using electrical resistivity tomography (ERT) and Ground Penetrating Radar (GPR).
This expedition is a collaborative effort involving 33 officials from six state departments, two central government agencies (Geological Survey of India, Central Water Commission), 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 essential ground support, including medical assistance.
The key objectives include slope stability assessment to evaluate the risk of mass movements around the lakes, a morphometric survey to map and measure the physical characteristics of the lakes and their surroundings, and lake discharge measurement to understand the hydrology and outlet flow dynamics.
The team will also conduct 3D terrain mapping using UAV/Drone technology to create high-resolution terrain models.
The Science and Technology Department, led by Secretary Sandeep Tambe, will focus on bathymetric investigations and hydrodynamic modeling to identify flood-prone areas downstream. The Mines and Geology Department, under Secretary Dicky Yangzom, will conduct geophysical investigations to assess sub-surface geology, moraine materials, and potential hazards. The Geological Survey of India will perform landform, geomorphological, and geotechnical studies, including rock classification and fault zone analysis. Sikkim University will survey moraine sediments, vegetation, and monitor permafrost in the moraine complex.
The expedition’s findings will contribute to a comprehensive understanding of Glacial Lake Outburst Flood (GLOF) risks and inform future mitigation efforts.
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