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Rebuilding the Teesta-3 Dam
Context:
On January 27, 2025, an expert committee of the Ministry of Environment, Forests and Climate Change recommended rebuilding the Teesta-3 dam on the Teesta River in Sikkim.
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- A powerful glacial lake outburst flood (October 2023) from South Lhonak Lake destroyed the dam and hydroelectric facility.
- Over 100 people were killed, and more than 80,000 people across four districts were affected.
Details of the GLOF
- The moraine failure sent rocks into the lake, triggering a strong ripple and sending 50 billion litres of water into the valley.
- The flood carried dam debris downstream, worsening destruction.
- This also caused multiple landslides 30-40 kilometers downstream.
Impact of Global Warming
- Accelerated Glacier Melting: Global warming and black carbon (soot) are melting Himalayan glaciers rapidly. As glaciers shrink, melting speeds up, increasing water accumulation in glacial lakes.
- Expanding Glacial Lakes: A 2024 Central Water Commission report found a 10.8% rise in the number of Himalayan glacial lakes since 2011. Their total surface area increased by 33.7% in the same period.
- The South Lhonak Lake, formed in the early 1960s, had grown to 167 hectares by 2023.
- Geological Instability: Glacial retreat destabilises geological formations, further increasing risk in the region.
Concerns Over Rebuilding Teesta-3
- Questionable Justification: The committee cited Teesta-3’s “success” and “commercial viability” pre-GLOF. The dam’s power-generating equipment remained largely intact. Critics argue this reasoning ignores climate risks and ecological concerns.
- Ongoing Legal and Regulatory Issues: Public interest litigations have called for Teesta-3’s scrapping due to:
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- It is located in an earthquake- and landslide-prone area.
- Techno-economic clearance issues.
- Non-compliance with a 1996 notification requiring Sikkim to hold 51% equity.
- Alleged corruption.
Teesta-3 Dam 2.0 Design
- The committee proposed rebuilding the dam with a more robust design:
- A new dam will be built entirely with concrete, replacing the previous concrete-rock mix.
- Spillway volume to be nearly three times larger.
- An early-warning system for flooding is to be implemented.
- Climate-Based Design Considerations: India Meteorological Department modelled a “worst-case scenario” based on projected maximum rainfall for the next century. Critics argue rainfall alone is an inadequate predictor of GLOF risks.
Expert Concerns on Risk Multiplication
- Complex Risk Factors: The 2023 GLOF may not have been caused by heavy rain; local weather stations recorded only moderate rainfall. Other risk factors include:
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- Erosion and sediment transport.
- Riverbank collapses and landslides.
- Impact of sediment movement on water levels.
- International Expert Assessment (January 30, 2025): A study by IIT Bhubaneswar, IISc Bengaluru, Indo-Tibetan Border Police, and the Sikkim government stated that existing GLOF models fail to account for key erosion and sediment transport processes.
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- Water waves move faster than sediment waves, increasing the risk of unexpected flooding dynamics.
Commercial Viability vs. Public Safety
- Power Demand Consideration: India’s rising electricity demand makes hydropower attractive. However, hydropower must be balanced against disaster risks.
- Potential Risks of Teesta-3 2.0: If the dam fails in another GLOF, the destruction downstream could be even worse. A new facility with additional features also introduces new failure modes.
Broader Socio-Economic and Environmental Implications
- Need for Social Security Measures: Local residents need economic and health security to withstand disasters. Disaster response should prioritise rebuilding lives, not just infrastructure.
- Long-Term Sustainability Questions: Urban planning expert Brian Stone, Jr. argues “We cannot engineer our way out of climate change; retreat is inevitable.”
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- Over time, either disaster-prone areas will shrink, or the cost of maintaining infrastructure in such areas will rise.
Way Forward
- Risk Assessment Framework Needed: Decisions should prioritise minimising local risk over commercial viability. A structured risk determination matrix should define acceptable risk levels.
- Transparent Cost-Benefit Analysis: The true cost of disaster preparedness must be included in power tariffs. Externalising these costs for short-term financial viability is unsustainable.
- Reconsideration Urged: Given climate risks, public opposition, and scientific uncertainty, the rebuilding of Teesta-3 demands a more thorough assessment before moving forward.
About Teesta River
- Also Known As: Torsa River (in Bangladesh)
- Origin: Pauhunri Glacier, Eastern Himalayas, Sikkim, India
- Course: Flows through Sikkim & West Bengal → Enters Bangladesh → Merges with Brahmaputra near Gaibandha
- Transboundary river between India & Bangladesh
- Length: ~414 km
- Main Tributaries:
- Right-bank: Zemu Chhu, Rangyong Chhu, Rangit River
- Left-bank: Lachung Chhu, Chakung Chhu, Dik Chhu, Rani Khola, Rangpo Chhu
