Expanding Glacial Lakes in the Indian Himalayas

News Excerpt: 

The Indian Space Research Organisation’s (ISRO) long-term satellite imagery covering the catchments of Indian Himalayan river basins from 1984 to 2023 have shown significant changes in glacial lakes.

More about news :

  • The Himalayan Mountains, often referred to as the Third Pole because of their extensive glaciers and snow cover, are highly sensitive to changes in the global climate, 
    • Both in terms of their physical characteristics and their societal impacts. 
  • Glaciers across the globe have been experiencing unprecedented rates of retreat and thinning since the onset of the Industrial Revolution in the eighteenth century.
  • This retreat leads to the formation of new lakes and the enlargement of existing ones in the Himalayan region. 
    • Glacial lakes play a crucial role as freshwater sources for rivers in the Himalayan region.
    • However, they also pose significant risks, such as Glacial Lake Outburst Floods (GLOFs), which can have devastating consequences for communities downstream. 
  • GLOFs occur when glacial lakes release large volumes of meltwater due to the failure of natural dams, such as those made of moraine or ice, resulting in sudden and severe flooding downstream. 
  • Monitoring and studying the occurrence and expansion of glacial lakes in the Himalayan region is challenging due to inaccessible and rugged terrain. 
  • Satellite remote sensing technology proves to be an excellent tool for inventory and monitoring due to its wide coverage and revisit capability. 
  • Satellite data archives spanning the past 3 to 4 decades provide valuable insights into changes occurring in glacial lakes in the Indian Himalayan region.
    • Of the 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes have notably expanded since 1984.

  • Among the expanding glacial lakes, 130 are situated within India, with 65, 7, and 58 lakes located in the Indus, Ganga, and Brahmaputra River basins, respectively.
    • 601 lakes (89%) have expanded more than twice.
    • 10 lakes have grown between 1.5 to 2 times.
    • 65 lakes at 1.5 times.
  • Elevation-based analysis reveals that 
    • 314 lakes are located in the 4,000 to 5,000 m range and 296 lakes are above 5,000 m elevation.
  • The glacial lakes are categorized based on their formation process into four broad categories, 
    • Moraine-dammed (water dammed by moraine).
    • Ice-dammed (water dammed by ice).
    • Erosion (water dammed in depressions formed by erosion). 
    • Other glacial lakes. 
  • Among the 676 expanding lakes, the majority of them are Moraine-dammed (307) followed by Erosion (265), other (96), and Ice-dammed (8) glacial lakes, respectively.
  • Long-term changes in the Ghepang Ghat glacial lake (Indus River Basin) at an elevation of 4,068 m in Himachal Pradesh, 
    • India, shows a 178% increase in size from 36.49 to 101.30 hectares between 1989 and 2022. The rate of increase is about 1.96 hectares per year.
  • Satellite-derived long-term change analyses provide valuable insights for understanding glacial lake dynamics, which are essential for assessing environmental impacts, GLOF risk management, and climate change adaptation in glacial environments.

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