Kolkata/Kochi: At least 15 people are thought to be dead after a cloudburst over Lhonak Lake in north Sikkim resulted in a flash flood in the Teesta river.The state is “reeling under a huge disaster” said Sunita Khatiwara, a native of south Sikkim who is currently a project officer at the Forest and Environment Department in Gangtok. Reports are coming in that a Glacial Lake Outburst Flood (GLOF) – triggered by the cloudburst above the South Lhonak glacial lake in North Sikkim – caused the Chungthang Dam breach and the flooding downstream of the Teesta river basin, Khatiwara said.This flood was exacerbated by the release of water from the Chungthang dam, according to some locals.Army vehicles parked near Bardang, close to Singtam, were swept away. Twenty three personnel were reported missing, and some vehicles are believed to be submerged under the slush. The Army’s Eastern Command issued a statement indicating that some establishments along Lachen Valley have been affected. Several of Khatiwara’s immediate relatives living downstream of the flood areas are currently in relief camps because their houses are flooded, she told The Wire. Power cuts are a concern in the town, and so is poor data networks, which make communication difficult. Apart from these, incessant rain is delaying rescue and relief work too, she added.Assistant District Magistrate of Mangan, Sonam Tashi, said mobile towers may have been affected.‘Hazardous’A study in 2020 listed the South Lhonak lake as among the 10 lakes posing the highest GLOF threats among the 36 glacial lakes in the North Sikkim that the study shortlisted as “hazardous” based on several geological parameters. The Lake has also been expanding over the years, several studies show. The culprit: climate change. As temperatures rise due to global warming, glaciers are retreating, or getting smaller. In turn, the lakes attached to them – glacial lakes – are increasing in area. One study found that the South Lhonak Glacial Lake in the Upper Teesta Basin is growing at an average aerial expansion of 0.03 square km per year. The 2020 study found that the Lhonak Lake increased in size by 0.205 square km between 2000 and 2018 alone.The Lhonak Lake increased in size by 0.205 sq km between 2000 and 2018. Photo: Nazimul Islam & Priyank Pravin Patel (2021): Inventory and GLOF hazard assessment of glacial lakes in the Sikkim Himalayas, India, Geocarto International, DOI: 10.1080/10106049.2020.1869332In fact, warmer temperatures are also causing the formation of more glacial lakes in the upper reaches of the Teesta river in the district of Northern Sikkim. The 2020 study found that 203 new lakes have formed in the region between 2000 and 2018. Of these, 82 were born between 2011 and 2018 alone. The overall area under lakes in North Sikkim has increased by a shocking 6.9 square km between 2000 to 2018 (a rise of 37.5%).Another study in 2021 mapped infrastructure exposed to GLOFs in the Teesta valley and found that “many settlements and assets located along the river channel at Chungthang are potentially exposed to future GLOFs, indicating the need to conduct a full environmental impact assessment and potentially undertake GLOF risk mitigation measures”.Images released by @isro confirming that South Lhonak lake burst. So this is confirmed to be a GLOF event now.Teesta III hydroelectric project in Chungthang, Sikkim was overwhelmed by a GLOF event. Sobering, all those years of paper warnings come true in real life.… pic.twitter.com/55sLGs6VQv— Anand Sankar (@kalapian_) October 4, 2023The Teesta River flows through Sikkim and West Bengal before entering Bangladesh.Numerous houses, hotels and tourist facilities are understood to be affected. West Bengal’s Siliguri and Jalpaiguri districts are also part of the red alert that has been issued. Evacuations are in progress for residents living near the river and in hill areas.Although the intensity of the rainfall has slightly decreased, communication remains disrupted in a significant portions of North Sikkim.“Many migrant labourers and locals living near the river are swept away. The administration and the army are trying to rescue people. We can not estimate the extent of the loss now. This is a seismic zone, prone to earthquakes and landslides. We need to introspect our handling of the Himalayas,” said Navin Kiran, a Gangtok based socio political activist currently in the affected zone, Rangpo. ProjectsThe Chungthang Hydro-Dam is a crucial component of the 1200-megawatt Teesta Stage III Hydro Electric Project, which was developed by Teesta Urja. This project was commissioned in 2017, at an estimated cost of Rs 14,000 crore.The construction process for this project had involved blasting activities and the boring of tunnels.“After the Kedarnath disaster, tourism operators in Sikkim had, in fact, filed an RTI to understand the condition of the dams in the state. The government had said that out of the 12 dams in Sikkim, seven are in a vulnerable condition,” said environment activist Mukut Biswas, who heads the Prameya Foundation.Environmentalists have been expressing serious concerns about the construction of large-scale infrastructure projects in the Eastern Himalayas, particularly the building of multiple dams. This region is situated in seismic zones IV and V, which are known to be highly susceptible to earthquakes. There have also been warnings from ecologists regarding the ongoing 45 km-long Sivok-Rangpo rail project. This railway project aims to connect the Sivok railway station in Darjeeling district of West Bengal, to Rangpo in East Sikkim and involves the construction of several tunnels. One of the construction train stations under construction was damaged in the flash floods.Impact on ecologyThe South Lhonak glacial lake was already known to be extremely vulnerable and the ecological impacts of this disaster would be “unprecedented”, Khatiwara told The Wire. The GLOF occurred in the Kanchendzonga Biosphere Reserve, which is home to many rare and endangered wildlife, the wildlife biologist noted. “An assessment is already underway and all concerned officers have been instructed by forest officials to conduct a detailed assessment,” Khatiwara told The Wire.The Reserve, for instance, is home to the species including the snow leopard and more than 35 species of rhododendron, the state tree of Sikkim. The Reserve was added to the list of UNESCO World Heritage Sites in 2016, and is the first “mixed” heritage site in India because it meets both cultural and natural heritage criteria. Indigenous communities including the Lepchas and Bhutias consider Mount Khangchendzonga, which lies within the Reserve, as sacred. (With inputs from Aathira Perinchery)
