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Source: ICIMOD

Context

India has initiated a national program to monitor and manage Glacial Lake Outburst Flood (GLOF) threats, prioritizing 195 high-risk lakes in the Himalayan region in the face of escalating climate-related disasters.

What is a Glacial Lake Outburst Flood GLOF?

• A glacial lake outburst flood  GLOF is the rapid release of a large amount of water from a glacial lake, which can be caused by a variety of events including glacier melting, avalanches, and earthquakes.  
• GLOFs are primarily generated by water accumulating in a glacial lake and being trapped in place by ice or debris.  
• When water pressure reaches a critical level, it might burst the natural dam, flooding the downstream area with large amounts of water, debris, and rock. 
• GLOFs can be highly devastating, causing major damage to infrastructure, property, and human lives.  
• Floods can occur suddenly and unexpectedly, causing floods, landslides, and mudflows downstream.  
• GLOFs can be especially damaging in mountainous places, where the geology and steep terrain can increase the force and velocity of the floodwaters.

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Source: Chanakya Mandal

Rising GLOF Threat in the Himalayas

Glacial Lake Outburst Floods (GLOFs) occur when unstable glacial lakes, created by melting glaciers, suddenly breach, releasing massive volumes of water downstream. In the Indian Himalayan Region (IHR), two key types of glacial lakes are identified:

• Supraglacial Lakes: Located on glacier surfaces, these are highly vulnerable to rapid melting during summer.
  
  
• Moraine-Dammed Lakes: Found near the glacier’s snout and held back by loose moraine (debris), these are extremely prone to sudden collapse triggered by avalanches or the instability of ice cores.
  
  

According to India’s National Remote Sensing Centre, the country hosts nearly 28,000 glacial lakes, most situated above 4,500 metres. Their high-altitude locations make physical access challenging and monitoring efforts limited.

Past Disasters and Increasing Risks

India has already faced multiple GLOF-induced disasters, including:

• Chorabari GLOF (2013): Triggered the Kedarnath floods and landslides, resulting in hundreds of deaths.
  
  
• South Lhonak GLOF (2023, Sikkim): Breached the 1,250 MW Chungthang dam, raising the Teesta riverbed and reducing its capacity to carry water.
  
  
• The threat is intensifying due to rising global temperatures, with 2023 and 2024 recorded as the hottest years globally, accelerating glacier melt and destabilising lake structures.
• Moreover, the absence of adequate weather and hydrological monitoring stations in these remote, high-altitude regions has left the majority of glacial lakes unmonitored and vulnerable.

Impacts of GLOF

• Human Impact: GLOFs can kill, injure, and displace people.  Communities downstream of glacial lakes are especially vulnerable to abrupt floods.
• Floodwaters bringing debris, rocks, and ice can cause significant damage to roads, bridges, hydropower plants, and other infrastructure along river basins.
• Economic Losses: The destruction of infrastructure and disruption of economic operations can cause major economic losses in impacted areas.
• Environmental consequences: GLOFs have the potential to modify river channels, deposit sediments, and have an influence on downstream habitats and biodiversity.  They may also contribute to water quality problems.

Source: The Hindu