Glacial Lake Outburst Floods (GLOFs)

On July 8, 2025, a Glacial Lake Outburst Flood (GLOF) originating in Tibet caused devastation in Nepal, highlighting transboundary vulnerabilities and climate-induced risks in the Himalayas.

Understanding GLOFs and Their Triggers

• What is a GLOF?
  • A Glacial Lake Outburst Flood (GLOF) is a sudden release of water from a glacial lake due to dam failure, often leading to catastrophic downstream flooding.
• Types of Glacial Lakes in the Himalayas

• • Supraglacial Lakes: Formed on glaciers; prone to melting during high summer temperatures.
  • Moraine-Dammed Lakes: Blocked by loose sediment or ice; vulnerable to sudden collapse due to structural weakness.
• Major Triggers
  • Ice or rock avalanches, Earthquakes, Excessive glacial meltwater pressure, Landslides into glacial lakes etc.

GLOF Impacts in Nepal and the Himalayas

• July 2025 Event
  • Washed away a China-built bridge on the Lende River in Nepal
  • Damaged four hydroelectric plants, cutting off ~8% of Nepal’s power supply
  • Lack of early warning from China cited by Nepalese officials
• Previous GLOF Incidents in Nepal
  • Solukhumbu (2024), Mustang (2025), Humla (2025)
  • Historical Cases: Cirenma Co (1981), Dig Tsho (1985), Tama Pokhari (1998)
  • Demonstrates a repeated pattern of high vulnerability without transboundary alert mechanisms

India’s GLOF Vulnerability

• Geographic Exposure
  • 28,000+ glacial lakes in Indian Himalayan Region (IHR)
  • Over 7,500 lakes above 4,500m; inaccessible for most of the year
  • Risk hotspots: Sikkim, Uttarakhand, Himachal Pradesh, Ladakh, Arunachal Pradesh
• Recent Incidents
  • Sikkim (2023): South Lhonak GLOF damaged the $2 billion Chungthang Dam
  • Kedarnath (2013): Chorabari lake outburst, compounded by cloudbursts and landslides — caused massive devastation
• Environmental and Infrastructure Risks
  • Riverbed siltation (Teesta), dam failures, and displacement of communities
  • Increased frequency due to record global temperatures (2023–2024 were hottest years globally)

India’s National Response and Mitigation Strategy

• NDMA & CoDRR Initiatives
  • Shift from reactive to proactive disaster risk reduction
  • Committee on Disaster Risk Reduction (CoDRR) formulated a national strategy
• Key Features of the National Programme
  • $20 million initiative for 195 at-risk glacial lakes
  • Risk categorized in four levels
  • Five-fold objectives:
    • Hazard Assessment
    • Automated Weather and Water Stations (AWWS)
    • Early Warning Systems (EWS)
    • Risk Mitigation (e.g., drawdown channels, retention walls)
    • Community Engagement
• Use of Technology
  • Synthetic Aperture Radar (SAR) Interferometry: Detects micro-changes in slope stability
  • Electrical Resistivity Tomography (ERT): Assesses moraine dam integrity
  • UAVs and Bathymetric Surveys: Determine lake volume and topography
• Field Implementation
  • Expeditions to 40 high-risk lakes in 2024
  • Local communities engaged to ensure cultural and ecological sensitivities are respected
  • Monitoring stations in Sikkim providing near real-time lake data every 10 minutes

Challenges Identified

• Lack of Transboundary Early Warning: No formal mechanism with China despite repeated cross-border GLOFs
• Data Deficiency: Inadequate monitoring stations; surveys possible only in brief summer window
• Technological Gaps: Limited indigenous innovation and underutilisation of advanced geospatial tools
• Community Disconnect: Cultural resistance and inadequate awareness among local populations

Way Forward

• Bilateral/Regional Cooperation: Formalise early warning agreements with China, Nepal, and Bhutan through multilateral platforms (e.g., BIMSTEC, SCO)
• Technological Investment: Expand use of SAR, UAVs, EWS and geospatial modelling tools in IHR
• Local Capacity Building: Involve local communities, NGOs, and mountaineering institutions in field surveillance
• Policy Integration: Align glacial risk mapping with national climate adaptation and infrastructure planning
• Cryosphere Research Funding: Support Indian R&D institutions for long-term climate-glacier-disaster research synergy