The recent deadly flash flood in the north-east state of Sikkim, India, has highlighted the urgent need for advanced early warning systems for glacial lakes. The flood, caused by the burst of the South Lhonak glacial lake in the Himalayas, has claimed the lives of at least 70 people and left over 100 others missing. The sudden release of water from glacial lakes can be triggered by heavy rains, earthquakes, or avalanches. Implementing an early warning system can help authorities evacuate people in time and minimize damage by opening floodgates from downstream dams. However, despite the known risk of the South Lhonak lake, there was no functioning early warning system in place.
One possible cause of the outburst at South Lhonak is the failure of the moraines, which are loose boulders, rocks, and soil at the edge of the glacial lake. Studies had previously warned about the high probability of the lake flooding, as its area had expanded significantly due to the rapid melting of the glacier that feeds it. In 2016, some measures were taken to draw out water from the lake to prevent overflow, but no early warning system was established.
The impact of climate change, specifically global warming, is exacerbating the dangers of glacial lakes. Glaciers are melting at an accelerated rate, leading to increased water levels and the formation of new lakes or the fusion of existing ones. These lakes become highly susceptible to flooding, triggered by rockfalls, cloudbursts, or avalanches. The National Disaster Management Authority (NDMA) of India plans to install early warning systems for real-time alerts at most of the 56 at-risk glacial lakes in the country.
Nevertheless, the slow progress in setting up early warning systems raises concerns about bureaucracy and the involvement of multiple national and international agencies. The sensitive location of the South Lhonak lake, bordering China’s autonomous region of Tibet, might also contribute to delays in setting up a warning system due to military sensitivities. However, glaciologists emphasize the urgency of constant monitoring and risk-mitigating actions, as climate-induced changes are occurring rapidly in the Himalayan region.
Glacial lakes pose an increasing threat as the climate becomes warmer. While fast-melting glaciers and their rapid filling of glacial lakes were traditionally seen as the main concern, the thinning and retreating of glaciers lead to geological instability, including rockfalls and avalanches. Rising temperatures also result in rain at higher altitudes, causing further instability in mountainous regions like the Himalayas. Thawing of permafrost can lead to slope failures, which can trigger glacial lake floods.
To effectively prevent disasters caused by glacial lake floods, it is crucial to combine monitoring efforts with the installation of early warning systems, community involvement, and equipment maintenance. Time is running out, and immediate action is needed to protect vulnerable communities and mitigate the risks associated with glacial lakes. It is essential for India, as well as other countries facing similar challenges, to prioritize the implementation of advanced early warning systems and invest in effective risk management strategies.
