Context

• The recommendation to rebuild the Teesta-3 dam in Sikkim, following its destruction by a Glacial Lake Outburst Flood (GLOF) in October 2023, has sparked intense debate.
• While the project was previously deemed successful and commercially viable, its reconstruction raises critical environmental, geological, and socio-economic concerns.
• Therefore, it becomes imperative to examine the factors that led to the Teesta-3 dam’s destruction, expert concerns regarding risk assessment, and the broader implications for sustainable infrastructure planning in a rapidly changing climate.

The Destruction of Teesta-3: Causes and Consequences

• The Teesta-3 hydroelectric dam was destroyed when a moraine on the South Lhonak lake’s flank suffered a slope failure, leading to a catastrophic flood.
• Satellite data revealed that approximately 50 billion liters of water spilled into the valley, triggering multiple landslides and extensive downstream damage.
• Over 100 lives were lost, and more than 80,000 people across four districts were affected.
• The failure of the dam also exacerbated the destruction by amplifying the flood’s intensity with debris acting as a battering ram.
• Subsequent analyses revealed that the moraine’s instability was a significant contributing factor, and experts have since monitored the lake for further signs of collapse.
• The disaster underscored the risks posed by glacial lake expansions, particularly in the context of climate change and regional geological instability.

Concerns Surrounding the Reconstruction of Teesta-3

• Climate Change and the Growing Threat of GLOF
  • Global warming and increasing particulate pollution, especially black carbon or soot, have accelerated Himalayan glacier melt.
  • This process has led to the formation and expansion of glacial lakes, increasing the risk of GLOFs.
  • According to a 2024 report by the Central Water Commission, the number of glacial lakes and water bodies in the Himalayan region grew by 10.8% between 2011 and 2024, with their combined surface area increasing by 33.7%.
  • The South Lhonak lake itself expanded significantly since its formation in the 1960s, reaching 167 hectares by 2023.
  • Beyond simply increasing water volumes, glacial retreat also destabilises geological formations, creating new hazards.
  • The unpredictable interactions between melting glaciers, shifting landscapes, and atmospheric conditions make it difficult to model future flood risks accurately.
  • Given this backdrop, the decision to rebuild the Teesta-3 dam appears questionable, especially as climate change acts as a risk multiplier, intensifying the frequency and severity of extreme weather events.
• Expert Concerns and Limitations of Risk Assessment
  • Insufficient Model for Capturing the GLOF Dynamics
    • The expert committee recommending the dam’s reconstruction justified its decision based on the previous facility’s success and the largely intact condition of its power-generating equipment post-GLOF.
    • The new design incorporates several improvements, including a fully concrete structure, a spillway nearly three times larger, and an early-warning system.
    • However, these modifications rely heavily on rainfall-centric models, which experts argue are insufficient for capturing the complexities of GLOF dynamics.
  • Risk Assessment Limitations
    • A 2025 assessment by an international team of scientists from institutions such as IIT Bhubaneswar and IISc Bengaluru highlighted critical gaps in existing flood models.
    • Their report stressed that prevailing approaches fail to adequately account for erosion, sediment transport, riverbank collapses, and hillslope-channel interactions, factors that significantly influence flood behaviour.
    • Additionally, Professor Raghu Murtugudde has noted that climate models struggle to accurately represent extreme rainfall events, further complicating risk assessments.
    • Given these uncertainties, many environmental activists and hydrogeologists have raised concerns about the wisdom of rebuilding Teesta-3 in an earthquake- and landslide-prone region.
    • Public interest litigations have also questioned the dam’s compliance with regulatory norms, including issues related to Sikkim’s mandated equity share and allegations of corruption.

Necessary Measures to Mitigate the Concerns

• Balancing Energy Needs and Climate Risks
  • India’s growing energy demand necessitates an expansion of power production, and hydroelectric projects like Teesta-3 offer a renewable energy source.
  • However, climate change multiplies risks, making the siting of such projects a crucial concern.
  • While Teesta-3’s new design may mitigate damage in the event of a similar flood, it remains vulnerable to stronger or differently structured floods.
  • Moreover, its reconstruction introduces new technological and structural risks that could lead to unforeseen failure modes.
  • Critics argue that commercial viability alone should not dictate the decision to rebuild. Instead, infrastructure planning must prioritise minimizing risks to local communities and maximizing their socio-economic resilience.
  • This includes ensuring robust disaster preparedness measures, social security frameworks, and emergency response systems.
• A Sustainable Approach to Infrastructure in the Himalayas
  • The debate surrounding Teesta-3 aligns with broader discussions on infrastructure sustainability in disaster-prone areas.
  • Brian Stone Jr., a professor at the Georgia Institute of Technology, has argued that engineering solutions alone cannot counteract climate change; at some point, retreat becomes inevitable.
  • If the risks associated with an area continue to rise, either the area itself must be abandoned, or the costs of maintaining infrastructure must increase significantly.
  • A more sustainable approach would involve integrating climate risk assessment directly into infrastructure planning.
  • This could include developing a risk determination matrix with clear thresholds for unacceptable risk levels.
  • Additionally, the costs of disaster preparedness and mitigation should be factored into the hydroelectric power tariff rather than externalized, ensuring long-term sustainability. 

Conclusion

• The decision to rebuild the Teesta-3 dam highlights the complex intersection of energy needs, environmental risks, and socio-economic considerations.
• While the project promises renewable energy and economic benefits, its location in a geologically unstable, climate-sensitive region raises serious concerns.
• As climate change continues to amplify risks, infrastructure planning must evolve beyond commercial viability to prioritize resilience, risk reduction, and sustainability.