Is India prepared for the next Glacial Lake Outburst Flood? Nepal catastrophe brings 200 high-risk lakes in focus

The deadly glacial disaster in Nepal has sharpened a question India can no longer afford to leave unanswered: how prepared is the country for a similar chain reaction from its own Himalayan glacial lakes? The issue assumes urgency with around 200 high-risk glacial lakes identified across India's Himalayan region, as reported by TOI's Pradeep Thakur.

The Himalayan ranges in India are home to about 7,500 glacial lakes, according to a government survey, with roughly 10% located in Sikkim alone. Of these, 25 in Sikkim have been classified as very high-risk, highlighting the scale of the threat posed by rapidly changing mountain environments.

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The risk extends well beyond Sikkim. Around 4,700 glacial lakes lie within the Ganga river basin, whose catchment covers more than 2.5 lakh square kilometres. A breach of even one high-risk lake could unleash enormous volumes of water and debris into downstream valleys, threatening settlements, roads, bridges and critical infrastructure.

The concern is not hypothetical. India witnessed one of its most devastating Glacial Lake Outburst Flood (GLOF) disasters in recent years in Sikkim on October 3, 2023.

Glacial rocks measuring 14.7 cubic metres collapsed into South Lhonak Lake shortly before midnight, "generating a 20-m high displacement wave". The resulting flood tore through downstream areas, destroying hydropower infrastructure and settlements.

The Nepal disaster has now brought the vulnerability of the Himalayan region back into sharp focus, particularly because such events may not follow a single, predictable pattern.

Krishna Vatsa, member of the National Disaster Management Authority (NDMA), said the precise sequence behind the Nepal disaster was still being scientifically established but pointed to the rapidly escalating nature of such hazards.

"These are cascading hazards: an ice or rock failure can become a debris flow, create a temporary lake and then generate a flash flood. Such events can develop extremely rapidly and may provide very little warning time downstream."

India has identified the lakes. The next question is preparedness

India's response to the growing GLOF threat includes the National GLOF Risk Mitigation Programme, under which 195 at-risk glacial lakes have been identified. The programme focuses on five areas: assessment, monitoring, early warning, mitigation and community awareness.

But experts argue that identifying the lakes is only the first step.

"India's National GLOF Risk Mitigation Programme has marked 195 at-risk glacial lakes and follows five key priorities (assessment, monitoring, early warning, mitigation, community awareness). It needs to be speeded up and scaled up immediately as a priority for national security," said Syed Safi Ahsan Rizvi, an ex-NDMA member.

The government had moved to strengthen coordination after the South Lhonak Lake disaster. A high-level coordination committee on GLOF disaster risk reduction was established, with Prime Minister Narendra Modi's principal secretary PK Mishra spearheading the initiative.

The committee was tasked with bringing multiple agencies together, conducting surveys of glacial lakes and identifying those posing the greatest risk.

The Centre also allocated Rs 150 crore for the National GLOF Risk Mitigation Programme covering four Himalayan states with high-risk glacial lakes.

The coordination committee held its first meeting on disaster risk reduction in November 2024. At the meeting, Mishra expressed satisfaction with the group's "tri-focal lens: assessment, monitoring, and mitigation".

The committee subsequently held regular meetings and gathered feedback that was incorporated into a joint strategy involving the Centre and states. However, the follow-up actions and their implementation have not been clearly outlined.

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From mapping lakes to warning communities

The government had earlier said multi-agency expeditions were carried out to assess all "A-category" glacial lakes.

The teams brought together scientists and officials from the National Disaster Management Authority, Central Water Commission, Geological Survey of India, Centre for Development of Advanced Computing, Indo-Tibetan Border Police and the Army.

The scale of India's glacial-lake landscape, however, makes the challenge formidable. Thousands of water bodies are scattered across some of the world's most difficult terrain, while warming temperatures, unstable ice and changing precipitation patterns are increasing concerns about sudden failures.

The Nepal disaster has underscored why the distinction between simply knowing where high-risk lakes are and being able to detect a failure early enough to warn people downstream matters.

For India, the warning comes from a landscape it already knows is vulnerable. The South Lhonak disaster demonstrated how quickly a glacial collapse can transform into a devastating downstream flood. Nepal's catastrophe has added another dimension: a sequence involving ice or rock collapse, debris flow, temporary lake formation and a subsequent flood can unfold with little time for communities to react.

(With inputs from ToI)