The Teesta Dam and the Long Shadow of Climate Change

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.

Q1. What caused the destruction of the Teesta-3 dam in October 2023?
Ans. A Glacial Lake Outburst Flood (GLOF) from the South Lhonak lake, triggered by a moraine collapse, led to massive flooding that destroyed the dam.

Q2. How has climate change contributed to the rising threat of GLOFs in the Himalayas?
Ans. Rising temperatures accelerate glacier melting, leading to the formation and expansion of unstable glacial lakes, increasing the risk of sudden floods.

Q3. Why are GLOFs particularly dangerous compared to regular river floods?
Ans. GLOFs release massive amounts of water suddenly and at high velocity, carrying debris and triggering landslides, making them highly destructive and difficult to predict.

Q4. What key concern do experts have regarding the rebuilding of Teesta-3?
Ans. Experts worry that the new dam design relies too heavily on rainfall models and does not fully account for complex factors like glacier instability and sediment transport.

Q5. What alternative approach is suggested instead of rebuilding Teesta-3?
Ans. Experts suggest prioritizing risk reduction, monitoring high-risk glacial lakes, and considering retreat from disaster-prone areas rather than relying solely on engineering solutions. 

Source:The Hindu