Teesta Dam: Safety First

Teesta Dam: Safety First

Fourteen months after a devastating glacier lake outburst flood in Sikkim washed away the Teesta-3 dam and killed many people, an expert committee of the Environment Ministry has recommended that the dam be reconstructed.

Teesta-III Hydropower Project (Sikkim)

  • Type: Run-of-the-river hydropower project
  • Location: Chungthang, Sikkim
  • Capacity: 1,200 MW (largest hydropower project in Sikkim)
  • Dam Height: 60 meters
  • Commissioned: 2017
  • Developer: Teesta Urja Ltd. (TUL), with investment from Sikkim Government & private firms

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Key Recommendations of Expert Appraisal Committee (EAC)

  • Approval for Reconstruction of Teesta-III Dam: Proposal to reconstruct the Teesta-III dam with a new design, replacing the previous 60-metre-high concrete face rockfill dam with a 118.64-metre-high concrete gravity dam.
  • Enhanced Spillway Capacity: Increasing the spillway capacity of the dam from 7,000 cubic metres per second (cumecs) to 19,946 cumecs.
  • Early Warning System (EWS): Need for a robust Early Warning System (EWS) to monitor glacial lakes and flood risks in the upper catchment areas.
  • Relocation of Dam Control Room: To enhance the safety of personnel, relocating the dam control room to a higher elevation.
  • Comprehensive Study of Glacial Lakes: A detailed study of glacial lakes in the dam’s catchment area to assess potential GLOF risks.
    • Out of 119 glacial lakes identified, 13 were deemed potentially hazardous due to their size, volume, and proximity to the dam.
  • Landslide Mapping and Mitigation: Mapping landslides within a 5-kilometre radius of the Lachen and Lachung catchment areas.
  • Structural Resilience and Safety: Raised concerns about the structural resilience of the new dam and recommended a thorough review of the proposed modifications.
    • The design aspects of the dam, including its ability to withstand GLOF events and floodwaters, should be approved by the CWC, Geological Survey of India (GSI), and Central Soil and Materials Research Station (CSMRS).
  • National GLOF Risk Mitigation Programme: Supported the National GLOF Risk Mitigation Programme, which aims to reduce the risks posed by high-risk glacial lakes in the region.
    • The programme has identified 189 high-risk glacial lakes and allocated ₹150 crore for mitigation measures.

Dam Safety in Other Countries: USA, Australia, and China

  • USA: The National Dam Safety Program (NDSP) coordinates dam safety efforts between federal agencies, states, and private entities. 
    • The Federal Emergency Management Agency (FEMA) provides detailed guidelines for dam failure analysis, inundation mapping, and risk management, with data publicly available for transparency and research.
  • Australia: Australia uses a risk-based decision-making framework developed by the Australian National Committee on Large Dams (ANCOLD)
    • This framework informs dam design, location, and decommissioning decisions, ensuring that dams are built and managed based on their risk profiles.
  • China: Following multiple dam failures in the 1970s, China established the Dam Safety Management Centre and Large Dam Safety Supervision Centre to conduct dam failure analyses and consequence assessments
    • These analyses inform land-use regulations, early warning systems, and emergency management plans.

Key ecological and safety concerns regarding the Teesta-III hydropower project and its reconstruction

  • Increased Risk of Glacial Lake Outburst Floods (GLOF): Climate change is accelerating glacial melt, increasing the risk of more frequent and intense GLOF events that could again destroy the dam and cause downstream flooding.
    • The South Lhonak glacial lake burst in October 2023, causing catastrophic flooding that washed away the Teesta-III dam and killed over 40 people across four districts in Sikkim​.
  • Seismic Vulnerability and Risk of Landslides: The new dam is being approved without clearance from the Central Water Commission, Geological Survey of India, and Central Soil and Materials Research Station, raising serious safety concerns about its ability to withstand earthquakes and landslides.
    • In 2024, a landslide caused damage worth ₹300 crore to another hydropower project on the Teesta River, though it did not result in loss of life​.
  • Lack of Public Consultation and Local Opposition: Local communities, including indigenous groups, oppose the project due to its potential to disrupt their environment and livelihoods.
    • The new dam was approved without conducting a fresh public hearing, despite the massive impact on local communities​.
  • Environmental Degradation and Loss of Biodiversity: Dam construction will disrupt aquatic ecosystems, reduce fish populations, and alter river flow patterns, potentially harming agriculture and livelihoods downstream.
    • Large-scale deforestation for hydropower projects has already led to increased soil erosion and loss of biodiversity in Sikkim​.
  • Cost Overruns and Financial Viability: Given the high risk of future floods and structural failures, investing more in rebuilding a failed project may not be financially prudent.
    • The original Teesta-III project took 12 years to complete, exceeding its budget by 2.5 times​.
  • Weak Regulatory Oversight and Clearance Process: The lack of independent, transparent evaluations raises serious questions about regulatory oversight and environmental governance in India.
    • The Teesta-III project was cleared despite the lack of a revised Probable Maximum Flood (PMF) study, which is crucial for assessing future flood risks​.
  • Displacement and Impact on Local Communities: Hydropower projects often lead to the displacement of local communities and the destruction of their livelihoods, particularly in ecologically sensitive areas.
    • The Teesta-III project displaced several communities in Sikkim, with many losing access to agricultural land and fishing resources.

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Major dam failures in India

  • Teesta-III Dam, Sikkim (2023): A glacial lake outburst flood (GLOF) from South Lhonak Lake in Sikkim.
    • The flood washed away the 60-meter-high Teesta-III Dam, causing massive destruction and killing over 40 people​.
  • Machchhu-II Dam, Gujarat (1979): Heavy rainfall led to the dam’s overtopping and collapse.
    • The disaster caused a massive flood that killed over 2,000 people in Morbi, Gujarat.
  • Dhauliganga Dam, Uttarakhand (2021): A GLOF triggered by an avalanche from the Nanda Devi glacier led to extreme flooding.
    • The dam and hydropower project were severely damaged, killing more than 200 people.
  • Idukki Dam, Kerala (2018: Heavy monsoon rains and landslides in Kerala caused water levels to rise uncontrollably.
    • All five spillway gates were opened simultaneously for the first time, leading to catastrophic flooding.
  • Ukai Dam, Gujarat (2006): Uncontrolled water release due to extreme monsoon flooding.
    • The Surat floods submerged large parts of the city, causing massive economic losses.
  • Hirakud Dam, Odisha (2011): Excessive rainfall forced emergency water releases, causing downstream floods.
    • Thousands of homes were destroyed, and farmland was submerged.
  • Koyna Dam, Maharashtra (1967): A 6.5 magnitude earthquake struck the region.
    • The dam suffered structural damage, but did not collapse completely.

Dam Safety Regulations in India

Dam Safety Act, 2021

  • The Dam Safety Act, 2021 provides a comprehensive framework for surveillance, inspection, operation, and maintenance of large dams to prevent failures and ensure safe functioning.
  • Key Provisions of the Act
    • Institutional Mechanism
      • National Committee on Dam Safety (NCDS): Develops dam safety policies and standards.
      • National Dam Safety Authority (NDSA): Implements policies set by the NCDS.
        • Resolves interstate disputes over dam safety.
      • State Dam Safety Organizations (SDSO): Conducts regular inspections and safety monitoring of dams.
      • State Committee on Dam Safety (SCDS): Ensures compliance with safety measures at the state level.
    • Penalties for Non-Compliance: Imprisonment up to 2 years or fines for dam safety violations.

Other Major Initiatives for Dam Safety

  • Dam Rehabilitation and Improvement Project (DRIP)
    • Objective: Strengthen the structural safety of 736 dams across 19 states.
    • Funding: Supported by the World Bank and Asian Infrastructure Investment Bank (AIIB).
    • Implemented by:
      • Central Water Commission (CWC)
      • Damodar Valley Corporation (DVC)
      • Bhakra Beas Management Board (BBMB)
  • National Register of Large Dams (NRLD): Maintained by CWC.
    • Database of all large dams, including structural and operational details.
  • Dam Health and Rehabilitation Monitoring Application (DHARMA): Developed by CWC & National Informatics Centre (NIC).
    • Uses Artificial Intelligence (AI) for real-time monitoring of dams.
  • Seismic Hazard Analysis Information System (SHAISYS): Assesses seismic risks and their impact on dam structures.
  • National Centre for Earthquake Safety of Dams (NCESD)
    • Location: MNIT Jaipur, Rajasthan.
    • Purpose: Strengthen earthquake resilience of dams.
  • India Water Resource Information System (WRIS): Provides GIS-based water resource data, including dam conditions.

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India’s Constitutional arrangements and dam safety:

  • Entry 56 of List I: It deals with the Union’s legislative power relating to the regulation and development of inter-state rivers and river valleys.
  • Entry 17 of List II: secures the State’s legislative power over water. However, it is subject to Entry 56 of List I:  

Development of water resources and dams in India:

  • Role of State governments: Under the 7th Schedule of the Constitution of India, water and water storage is a state subject. 
    • Therefore, legislating dam safety is the responsibility of state governments.
  • Role of Central Government: Central Government can enact legislation governing dams in three scenarios:
    • If the project affects multiple states or international treaties: It can pass legislation regulating dams whose catchment area or downstream areas span multiple states or international borders.
    • If two or more states pass a resolution requiring such a law: In 2010, Andhra Pradesh and West Bengal passed resolutions requiring a law on dam safety. 
    • Environment Protection: Matters related to the protection of the environment under the Environment Protection Act, 1986.

Global Standards and India’s Compliance

  • International Commission on Large Dams (ICOLD): Founded in 1928, provides guidelines for dam design, construction, and monitoring.
    • Indian National Committee on Large Dams (INCOLD) interacts with ICOLD.
  • World Commission on Dams (WCD): Established by the World Bank & IUCN (1998) for dam effectiveness reviews.

About Glacial Lake Outburst Floods

  • A glacial lake outburst flood (GLOF) is a sudden and catastrophic release of water from a glacial lake
  • Glacial lakes are formed when meltwater from glaciers accumulates in depressions created by glacial activity, often dammed by natural barriers like moraines or ice. 
  • How GLOFs happen 
    • Glacier retreat: As glaciers retreat, they erode the valley floor and create depressions.
    • Lake formation: Meltwater from the glacier accumulates in the depressions, forming lakes.
    • Moraine dam: The lakes can be dammed by moraine, which is made of rocks, ice, and other debris pushed forward by the glacier.
    • Dam failure: The moraine dam can fail, causing the lake to suddenly release a large amount of water.
  • Triggering factors:
    • Climate change: Rising temperatures accelerate glacier melting, putting pressure on the ice and moraine dams, increasing the risk of failure. 
    • Avalanches: Falling ice or rock debris can destabilize the dam, triggering a sudden release of water. 
    • Earthquakes: Seismic activity can cause cracks in the dam, leading to a GLOF. 
    • Heavy rainfall: Excessive precipitation can rapidly increase water levels in the glacial lake, further stressing the dam. 
  • Impacts of a GLOF:
    • Massive flooding: A large volume of water is released rapidly, causing devastating floods downstream, destroying infrastructure and settlements. 
    • Landslides: The floodwaters can trigger landslides, further exacerbating the damage. 
    • Erosion: The sudden surge of water can severely erode the riverbed and banks. 

Issues Associated with Dam Safety in India

  • Aging Infrastructure & Poor Maintenance: Many Indian dams have outlived their design life, making them vulnerable to structural failures.
    • According to the National Register of Large Dams, India has a total of 5,745 dams, with 227 of them being over 100 years old
  • Seismic Vulnerability: Many Indian dams are located in earthquake-prone zones, making them high-risk structures.
    • The Koyna Dam (Maharashtra, 1967) suffered structural damage due to a 6.5-magnitude earthquake.
  • Flood & Overtopping Risks: Many dams have inadequate spillway capacity, leading to overtopping during extreme rainfall.
    • In October 2023, the Teesta-III Dam (Sikkim) was washed away by a glacial lake outburst flood (GLOF)​.
  • Sedimentation & Reduced Storage Capacity: Dams accumulate silt and sediment, reducing their water storage and flood control capacity.
    • According to a United Nations study, around 3,700 dams in India are projected to lose approximately 26% of their total storage capacity by 2050 due to the accumulation of sediment
  • Regulatory Weaknesses & Poor Oversight: Many states fail to comply with dam safety regulations, leading to ignored risks.
    • A CAG report on Gandhi Sagar Dam (MP) found that the State Dam Safety Organization (SDSO) ignored CWC recommendations​.
  • Lack of Early Warning Systems & Public Consultation: Many dams lack real-time monitoring and public involvement in safety decisions.
    • The Bihar Kosi floods (2008) worsened due to poor communication and lack of emergency response plans.

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Way Forward for Ensuring Dam Safety

  • Strengthen Regulatory Compliance & Enforcement: Ensure mandatory third-party safety audits for all large dams.
    • Empower the National Dam Safety Authority (NDSA) to impose stricter penalties for non-compliance.
  • Modernize Aging Dams & Infrastructure: Implement a National Dam Rehabilitation Plan under Dam Rehabilitation and Improvement Project (DRIP).
    • Strengthen seismic retrofitting for dams in earthquake-prone zones.
  • Improve Climate Resilience & Flood Management: Develop advanced flood forecasting models integrating satellite data & AI-based monitoring.
    • Implement catchment area treatment & afforestation to reduce siltation & soil erosion.
  • Establish AI-Based Early Warning & Emergency Preparedness: Expand Dam Health and Rehabilitation Monitoring Application (DHARMA) for automated structural health checks.
    • Deploy Seismic Hazard Analysis Information System (SHAISYS) for high-risk zones.
  • Enhance Public Participation & Transparency: Make dam safety data publicly available via India Water Resource Information System (WRIS).
    • Conduct regular stakeholder meetings for local awareness & disaster preparedness.
  • Strengthen Financial & Institutional Capacity: Increase budget allocation for dam maintenance & rehabilitation.
    • Secure international funding (World Bank, AIIB) for DRIP expansion.
  • Dam Decommissioning policy: This needs to be put in place for removing or reconstructing dams which cannot be repaired or upgraded.
    • It includes removal of hydro-electric generation facilities and recontouring of river channels through ecologically viable interventions in the catchment areas. 

Conclusion

Ensuring dam safety in India requires stronger regulations, modern infrastructure, climate adaptation, AI-based monitoring, public engagement, and financial commitment. By implementing these strategic measures, India can prevent future dam failures and protect lives, water security, and infrastructure.

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