Glacial Lake Outburst Floods Threaten Himalayan Regions
The Himalayan region witnessed severe Glacial Lake Outburst Floods (GLOFs) in 2025, causing widespread damage to infrastructure and power supply, especially in Nepal and India. Rising temperatures and melting glaciers have increased the frequency and intensity of GLOFs, posing a grave threat to life, property and ecosystems. The events show the urgent need for trans-boundary cooperation and advanced early warning systems to mitigate risks.
Recent GLOF Events in Nepal
On 8 July 2025, a major GLOF from a supra-glacial lake in Tibet triggered flash floods along the Lende river, damaging Nepal’s Rasuwagadhi inland container port and destroying a China-built friendship bridge. Four hydro-power plants on the Bhote Koshi river were rendered inoperable, cutting 8% of Nepal’s electricity supply. Nepalese scientists confirmed the lake’s surface area shrank from 63 to 43 hectares overnight. Later the same day, another GLOF struck Mustang district in Nepal. Earlier in 2025, GLOFs occurred in Humla and Solukhumbu districts, the latter destroying the Everest base camp village of Thame. These successive events tell Nepal’s vulnerability and the lack of early warning cooperation with China.
Types and Causes of GLOFs
Glacial lakes in the Himalayas are mainly of two types – supraglacial lakes on glacier surfaces and moraine-dammed lakes blocked by loose debris or ice cores. Most GLOFs result from ice avalanches, landslides or earthquakes that destabilise the lake dams. Rising temperatures accelerate glacial melt, increasing water volumes and pressure on weak moraine dams. The Himalayan region’s warming trend in 2023 and 2024 has heightened these risks, especially at high altitudes above 4,500 metres.
GLOF Risks in Indian Himalayan Region
India’s Himalayan region contains about 28,000 glacial lakes across 11 river basins. Approximately 7,500 lakes are in India, mostly in remote, high-altitude areas accessible only during short summer windows. Monitoring is limited due to terrain, costs and lack of infrastructure. The 2023 South Lhonak GLOF in Sikkim destroyed the $2 billion Chungthang hydropower dam and caused severe downstream flooding. The 2013 Chorabari GLOF triggered the Kedarnath disaster, causing massive casualties and damage. These events demonstrate the vulnerability of India’s infrastructure and communities to GLOFs.
Mitigation Efforts and Challenges
India’s National Disaster Management Authority (NDMA) has shifted focus from disaster response to risk reduction. It launched a $20 million programme targeting 195 high-risk glacial lakes. The programme includes hazard assessment, installation of Automated Weather and Water Stations (AWWS), early warning systems downstream, water level management, and community engagement. Scientific methods like SAR interferometry are being introduced to detect micro-changes in slope stability. Several expeditions have conducted bathymetry, Electrical Resistivity Tomography (ERT), UAV surveys, and established monitoring stations. However, challenges remain in accessibility, community trust, and technology deployment in harsh environments.
Need for Trans-boundary Collaboration
The 2025 Nepal floods exposed gaps in cross-border communication and early warning between China and Nepal. Many glacial lakes lie in trans-boundary watersheds, making joint monitoring and information sharing essential. Nepalese officials lament the absence of established early warning systems with Chinese authorities despite increasing risks. Effective collaboration could help prevent future catastrophes by ensuring timely alerts and coordinated responses.
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