The Teesta power project in Sikkim has witnessed another dam collapse, marking the second such incident in less than a year. On Tuesday morning, the Teesta Stage 5 dam, owned and operated by the National Hydroelectric Power Corporation (NHPC), sustained damage due to a landslide. Fortunately, no casualties have been reported as the power station was evacuated in recent days due to frequent landslides in the area.
The NHPC has dispatched an expert team from its corporate office to assess the situation, evaluate the extent of damage, and formulate plans for remedial work. The Stage 5 dam has been non-operational since October 2023 when a glacial lake outburst flood (GLOF) in the Teesta River basin severely damaged the Teesta Stage 3 dam, owned by Sikkim Urja Ltd. The cloudburst that triggered the GLOF led to a massive flash flood, washing away parts of the dam at Chungthang, Sikkim’s largest hydropower project.
The floodwater surged unabated through the Mangan district of North Sikkim. These catastrophic floods occur when glacial lakes, formed by melting ice, accumulate water behind fragile moraine dams. Unlike sturdy earthen dams, these moraine dams are susceptible to sudden collapse, releasing vast amounts of water within minutes or days, causing widespread devastation downstream.
According to NHPC, the Tuesday landslide at the 510 MW Teesta-V Power Station affected the hoist structure of the tail race tunnel (TRT) outlet, which channels water out of the power plant, and the GIS building, housing the high-voltage substation. The power plant remains inoperable and is undergoing restoration following the October 2023 flash flood.
Last October, NHPC informed stock exchanges that its two units—the Teesta-V power station (510 MW) and the Teesta-VI HE Project (500 MW)—were impacted by floods in Sikkim’s Lachen Valley. Sikkim has faced significant challenges this year due to persistent monsoon rains. In June, heavy rainfall lasting 36 hours triggered landslides and floods, claiming the lives of at least six people and stranding around 2,000 tourists in the Himalayan state.
During the four-month monsoon season (June-September), Sikkim has received 32% more rainfall than normal, exceeding India’s average precipitation by 4% (642.9 mm), as per the India Meteorological Department. The devastating impact of climate change on the Himalayan region is evident in the rising frequency of GLOFs. Last year, a Himalayan glacial lake outburst triggered floods in Sikkim, resulting in the deaths of 179 people. These events underscore the urgent need for robust infrastructure, early warning systems, and mitigation measures to protect lives and livelihoods in vulnerable areas.
