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Glacial Lake Expansion

Published: 3rd May, 2024

Context

The Indian Space Research Organisation (ISRO) recently released a satellite-data-based analysis shedding light on the expansion of glacial lakes in the catchments of Indian Himalayan river basins. This analysis comes amidst growing concerns about the risks of glacial lake outburst floods (GLOFs).

Insights from ISRO's Analysis:

  • ISRO's analysis, spanning four decades of satellite data from 1984 to 2023, revealed significant expansion in the size of glacial lakes within the Indian Himalayan region.
  • Out of the 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes had notably expanded since 1984, with 601 lakes more than doubling in size.
  • Approximately 130 of these expanded lakes are situated in India, particularly in the Indus, Ganga, and Brahmaputra river basins, a consequence of glaciers retreating due to global warming.

1: Dimension- Risks and Challenges:

  • Glacial lakes serve as vital freshwater sources for rivers but also pose risks, particularly GLOFs, which can result in sudden and severe flooding downstream.
  • Monitoring these lakes in the rugged Himalayan terrain is challenging, underscoring the importance of satellite remote-sensing technology for comprehensive monitoring and risk assessment.

2: Dimension- Mitigation Strategies:

  • The NDMA released guidelines on how to deal with disasters caused by GLOFs.
    • Identification and mapping of glacial lakes.
    • Using Synthetic-Aperture Radar imagery to automatically detect changes in water bodies, including new lake formations, during the monsoon months.
    • Methods could be developed to permit remote monitoring of lakes from space.
    • To manage lakes structurally, decreasing the volume of water with methods like controlled breaching, pumping or siphoning out water, and making a tunnel through the moraine barrier or under an ice dam.
  • Studies have explored strategies like using long High-Density Polyethylene (HDPE) pipes to syphon off lake water, as demonstrated in initiatives like reducing water levels in Sikkim's South Lhonak Lake.

Fact Box:

Formation of Glacial Lakes:

  • Glacial lakes are primarily formed by the accumulation of meltwater in depressions created by glacier movement.
  • ISRO categorizes glacial lakes into following types based on their formation mechanisms:
    • moraine-dammed
    • ice-dammed
    • erosion-based, and others

Glacial Lake outburst

  • When the boundary around unstable glacial lake breaks, and huge amounts of water rush down the side of the mountains, which could cause flooding in the downstream areas.
  • This is called glacial lake outburst floods or GLOF.
  • Factors causing GLOF: earthquakes, extremely heavy rains, landslides and ice avalanches.

 South Lhonak Lake·        

  • South Lhonak Lake is a glacial-moraine-dammed lake, located in Sikkim's far north-western region.
  • The lake is located at 5,200 m (17,100 ft)above sea level.
  • It formed due to the melting of the Lhonak glacier.

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