The Eastern Himalayan region is three times more at risk than any other region that is vulnerable to Glacier Lake Outburst Floods. Dr Kalachand Sain, Director, Wadia Institute of Himalayan Geology, says Himalayan regions provide ample opportunities for hydropower but require proper environmental impact assessment before tapping them. Such projects also need to be attached to early warning systems to reduce damage, he tells Jitendra Choubey in an interview. Excerpts:
What triggered the recent Glacier Lake Outburst Floods in Sikkim?
Based on pre- and post-disaster satellite images, there were multiple factors behind the Glacier Lake Outburst Floods (GLOF) in Sikkim. They include increase in lake water due to rapid melting of glaciers caused by global warming; snow/ice avalanches into the lake; heavy rainfall; and lateral moraine slump into the lake. Besides, there have been half-a-dozen moderate to strong magnitude earthquakes in western Nepal, approximately 700 km away from Sikkim. Their impact in triggering the GLOF cannot be underestimated. However, we cannot state that categorically unless we analyse the seismological data. Field work will definitely shed light on them.
What is the role of climate change in GLOF?
The Himalayas have the largest concentration of glaciers outside the polar regions. There is clear evidence of Himalayan glaciers melting at an unprecedented rate in recent decades under the influence of climate change. They are leading to the formation of new glacial lakes at the terminal ends behind the exposed end moraines. These are posing threat of GLOF.
Is there any trend in the frequency of GLOF in India or Himalayan countries?
Shrinking of glaciers and expansion of glacier lakes pose a threat of outburst. Furthermore, avalanches in the high-slope downstream pose threat to habitation and infrastructure. There are more than 20,000 glacial lakes in the Indian Himalayan region. But only large-size moraine-dammed lakes may be dangerous, like the Chorabari lake during the 2013 Kedarnath flash flood in Uttarakhand and the recent South Lhonak lake in Sikkim. There is no study that clearly describes the trend of frequent GLOF in India and other Himalayan countries. However, researchers from the University of Potsdam are of the opinion that the risk of GLOF in the eastern Himalayas is three times higher than in any other Himalayan region.
Is there a similarity between Uttarakhand and Sikkim tragedies in terms of environmental crisis?
There are some similarities with regard to the June 2013 Kedarnath disaster mainly caused by GLOF, the February 2021 Rishiganga-Dhauliganga deluge in Chamoli due to ice-rock avalanche, and the October 2023 Sikkim disaster caused by GLOF and dam burst. All of them were caused by flash floods, which damaged hydropower projects, bridges and roads, leading to loss of lives downstream. The triggering zones for these disasters are located in the basins dominated by snow and glaciers and glacier lakes.
Is there a figure on the potentially dangerous glacial lakes?
There are 503 glacial lakes in Indian Himalayan Region. Overall, glacial lake inventory by ICIMOD has marked 47 potentially dangerous glacial lakes.