Glacial Lake Outburst Flood (GLOF) in Sikkim

Publish Date : 01/11/2023

Sikkim recently experienced a Glacial Lake Outburst Flood (GLOF). The South Lhonak Lake, a glacial lake located at an altitude of 17,000 feet in the state’s northwest, experienced a rupture as a result of continuous rainfall.

  • Consequently, water was discharged into the downstream regions, causing flooding in theTeesta River and impacting four districts of Sikkim: Mangan, Gangtok, Pakyong, and Namchi, as reported by the Sikkim State Disaster Management Authority (SSDMA).
  • This flooding also caused the Chungthang Hydro-Dam in Sikkim (on Teesta river) to breach, worsening the overall situation.

What is Glacial Lake Outburst Flood?

  • About:
    • GLOF (Glacial Lake Outburst Flood)is a sudden and potentially catastrophic flood that occurs when water stored behind a glacier or a moraine (a natural accumulation of ice, sand, pebbles, and debris) is released rapidly.
      • These floods happen when glacial lakes formed by melting ice accumulate water behind weak moraine dams.
      • Unlike sturdy earthen dams, these moraine dams can fail abruptly, releasing large volumes of water in minutes to days, leading to devastating downstream flooding.
    • The Himalayan terrain,with its steep mountains, is particularly vulnerable to GLOFs.
      • Climate change, accompanied byrising global temperatures, has expedited the process of glacier melting in the Sikkim Himalayas.
        • The region now boasts more than 300 glacial lakes, with ten identified as susceptible to outburst floods.
      • GLOF can be triggered by several reasons, includingearthquakes, extremely heavy rains and ice avalanches.
    • Impact:
      • GLOFs can result in catastrophic downstream flooding.They have the potential to release millions of cubic meters of water in a short period of time.

How Susceptible is South Lhonak Lake to GLOFs?

  • TheSouth Lhonak lake in northern Sikkim is situated about 5,200 meters above sea level.
    • Scientists have previously warned that thelake had been expanding over years, possibly from the melting of the ice at its head.
    • Notably, seismic activities, including a 2011 magnitude 6.9earthquake, escalated the GLOF risk in the area.
  • In 2016, the Sikkim State Disaster Management Authorityand other stakeholders launched a critical plan to drain excess water from South Lhonak Lake.
    • Visionary innovator Sonam Wangchukled the effort, employing High Density Polyethylene (HDPE) pipes to siphon off water from the lake.
    • This initiative successfully reduced the lake’s water volume by approximately 50%, mitigating the risk to some extent.
  • However, the recent tragedy is believed to be caused by an avalancheoriginating from the ice-capped feature surrounding the lake.

What Actions be Taken to Reduce the Risk of GLOFs?

  • Glacial Lake Monitoring:Establishing a comprehensive monitoring system to track the growth and stability of glacial lakes in vulnerable regions.
    • Satellite imagery, remote sensing technology, andfield surveys through drones can be used to regularly assess changes in glacial lakes and their associated moraine dams.
  • Early Warning Systems:and early warning systems that can provide timely alerts to downstream communities in the event of a GLOF.
    • Also, there is a need to complement it withflood protection measures, such as constructing protective barriers, levees, or diversion channels to redirect floodwaters away from populated areas.
  • Public Awareness and Education:There is a need to raise public awareness about the risks of GLOFs and educate communities living downstream about evacuation procedures and safety measures, as per NDMA’s guidelines related to GLOF.
    • Conduct drills and training programs to ensure that residents know how to respond in case of a GLOF.
  • International Cooperation: India can collaborate with neighboring countries in the Himalayan region, as GLOFs can have transboundary impacts.
    • Sharing information and best practices for GLOF risk reduction and management with neighboring countries can help to mitigate the risk.