Why in news?
In early July 2025, Nepal experienced several glacial lake outburst floods that destroyed a Chinese‑built bridge and damaged hydropower projects. These incidents heightened concern about similar risks in the Indian Himalayas as rising temperatures melt glaciers and enlarge glacial lakes.
What are GLOFs?
- A glacial lake outburst flood occurs when a natural dam of ice or loose moraine holding back a lake collapses suddenly, releasing large volumes of water. These floods are high‑velocity and can devastate downstream communities, infrastructure and ecosystems.
Causes
- Climate change: Warming temperatures accelerate glacial retreat and lead to the formation of unstable lakes. Over 7,500 glacial lakes exist in India, many above 4,500 metres.
- Avalanches and landslides: Ice or rock falling into a lake can displace water and trigger a breach. Avalanches were implicated in the 2023 South Lhonak lake disaster in Sikkim.
- Heavy rainfall and cloudbursts: Intense monsoon downpours rapidly raise lake levels, stressing weak dams. The 2013 Kedarnath tragedy in Uttarakhand was linked to a cloudburst and subsequent GLOF.
- Seismic activity: Earthquakes can destabilise dams and trigger collapse, especially in seismically active zones like Uttarakhand and northeastern India.
- Human activities: Unregulated construction of roads and hydropower projects near glacier zones and climate‑warming emissions add to the risk.
Types of glacial lakes
- Supraglacial lakes: Pools that form on the surface of a glacier. They are prone to sudden drainage during summer melt.
- Moraine‑dammed lakes: Lakes held back by unconsolidated debris at the terminus of a glacier. Such lakes are unstable because the dams are weak and easily eroded.
Impacts
- Loss of life and property: GLOFs can inundate villages, damage roads, bridges and hydropower stations and displace communities.
- Environmental effects: Sudden influxes of water and debris raise riverbeds, alter courses and destroy habitats.
Response and mitigation
- National strategies: India’s National Disaster Management Authority has identified 195 high‑risk glacial lakes and initiated programmes to install automated weather stations, early warning systems and artificial drainage channels.
- Technological measures: Techniques like Synthetic Aperture Radar interferometry monitor glacier slopes, while electrical resistivity tomography helps map ice cores beneath moraine dams.
- Community involvement: Local communities are trained to monitor lakes, report anomalies and respect religious sensibilities when implementing structural measures.
Significance
- GLOFs highlight the cascading risks of climate change in the Himalayas. Studying and mitigating them is essential for protecting lives and infrastructure.
- Efforts to manage GLOFs also contribute to building resilience in mountain states and complement India’s broader climate‑adaptation strategies.
