General Studies Paper 3

Context:

• The recent glacial lake outburst flood (GLOF) in Sikkim wreaked havoc along the Teesta river, bringing into focus the magnifying risk of climate change induced GLOF across the Indian Himalayan Region.

Glacial lake outburst flood (GLOF)

• GLOF is a type of outburst flood caused by the failure of a dam containing a glacial lake.
• A study published in Nature this year indicates that 90 million people across 30 countries live in 1,089 basins containing glacial lakes. Of these, one­ sixth live within 50 km of a glacial lake and 1 km of potential GLOF run-out channels.
• In mountains, hazards often occur in a cascading fashion — heavy rainfall triggers a landslide, which may in turn cause a glacial lake outburst and more landslides downstream, and create conditions for flash floods.
• Predicting this chain of events is difficult. Institutional awareness of these risks is increasing, but the challenge is to evolve a system to mitigate risks from such hazards, and provide early warnings.

Early warning systems

• The magnitude of the tragedy that occurred on October 3 at the South Lhonak glacial lake in Sikkim is still unfolding. Scientists are gravitating towards the view that the key trigger in the process chain of the disaster was the collapse of a huge mass of rock/moraine from the north­western bank of the lake. It displaced a significant volume of melt water, widening the river mouth at the eastern end, resulting in flash floods.
• The Himalayan Region is susceptible to a range of hydro­meteorological, tectonic, climate and human induced mountain hazards. Each of them requires an extensive set of monitoring, mitigation, and early warning strategies. The process chain of glacial melting is adequately mapped. However, the multitude of glaciers and temporal variations in glacial recession makes monitoring and estimation of the risk more difficult.
• National Remote Sensing Centre’s (NRSC) Glacial Lake Atlas of 2023 showed that 3 major river basins, of the Indus, Ganga, and Brahmaputra, are host to above 28,000 glacial lakes. Of these, 27% are in India, in six States and Union Territories. This region has witnessed catastrophic GLOF events in the past few decades.
• Many geo­technical solutions for mitigation of GLOFs have been tried globally, including excavating channels for regulated discharge, drainage using pipes and pumps, spillway construction, and setting up small catchment dams to cut the speed of outflow. These measures are arduous and labour intensive, yet need to be implemented across high­ risk lakes.
• The most significant risk of such a disaster is to downstream hill communities and authorities who get a very short lead time to respond. They stand to suffer serious damage to life, property, and livelihood.
• Risks from glacial melting, slope shifting, landslides, intense precipitation, and heatwaves, among other hydro meteorological and geo­physical hazards, are rising. While meeting the development needs of hill communities, disaster and climate resilience principles need to be assimilated into government policy and practice as well as private investment.

Multi­disciplinary effort

• This requires an integrated, multi­disciplinary effort across institutions. NRSC’s atlases have provided high resolution data via remote sensing, which allows for monitoring spatial change.
• Central Water Commission (CWC) is conducting hydro-dynamic assessments of high risk lakes, mapping water flow, height and routing simulations using digital elevation models.
• NDMA’s national guidelines (2020) provide States with a technical overview of the hazard and risk zonation and suggest strategies for monitoring, risk reduction and mitigation.
• A comprehensive GLOF risk mitigation plan is in the final stages of approval and will include installation of monitoring and end to end early warning systems at high risk glacial lakes. In this endeavour, all governments and scientific institutions need to come together to integrate resources and capacities in disaster risk reduction.

Conclusion:

• While appropriate synergies have been created, increased focus on prevention and mitigation will reduce loss and damage and bring stability into the lives of hill communities.