India's Growing Glacial Lake Flood Risk: Lessons Three Years After the Sikkim GLOF
Three years have passed since the 4 October 2023 disaster in Sikkim, when a huge landslide fell into South Lhonak lake and caused a Glacial Lake Outburst Flood (GLOF) down the Teesta river. It officially killed 55 people, left 74 missing, displaced 7,025 people and affected about 80,000 people in around 100 villages. Total damage and losses were estimated at about ₹1,480 crore, including the destruction of the Teesta III hydropower dam at Chungthang.
A December 2025 global study counted 609 GLOF events from 1900 to 2020, with over 13,000 deaths. Such floods became much more frequent: from about 5.2 a year in 1981–90 to 15.2 a year in 2011–20.
In the Hindu Kush Himalaya (HKH) region, a September 2025 study (not yet peer-reviewed) found about 9,600 glacial lakes and 333 GLOF events between 1833 and 2024. India recorded 60 events and 6,119 deaths, the highest death toll in the region. About 70% of the region's events happened during the monsoon.
India's monitoring has grown. The Central Water Commission (CWC) expanded monitoring in June 2025 to 2,485 glacial lakes and 358 other water bodies across Himalayan river basins. A 2023 inventory by the National Remote Sensing Centre (NRSC) found 28,043 glacial lakes larger than 0.25 hectares.
The Union government approved ₹150 crore for the National GLOF Risk Mitigation Programme, run by the National Disaster Management Authority (NDMA). It covers Sikkim, Himachal Pradesh, Uttarakhand and Arunachal Pradesh, with work on early warning systems, controlled draining of risky lakes, weather stations and community awareness.
Experts say the money and plans must now reach the last mile. They call for real-time monitoring, evacuation plans, limits on building in flood-hazard zones, a national GLOF database and better coordination between the Centre, states and districts.
Glacial Lake Outburst Flood (GLOF)
A Glacial Lake Outburst Flood (GLOF) is a sudden, very powerful flood that happens when water held in a lake near a glacier suddenly breaks out. These lakes are often held back by weak walls of loose rock and ice. When the wall breaks, millions of cubic metres of water rush down the valley within minutes or hours, carrying rocks, mud and trees. A GLOF can travel tens of kilometres and destroy villages, roads, bridges and dams far below, often with very little warning.
The article marks three years since the South Lhonak GLOF and shows that both the number of glacial lakes and the frequency of GLOFs are rising. It argues that India's new monitoring and the ₹150 crore programme are steps forward, but must quickly reach the last mile through early warnings, evacuation planning and building rules.
Disaster Management Act, 2005
The Disaster Management Act, 2005 is the main law that sets up India's system for dealing with disasters such as floods, earthquakes, cyclones and GLOFs. It creates a chain of authorities at the national, state and district levels, each with clear jobs. It also provides for a special rescue force, a training institute and dedicated funds. The Act shifts India's focus from only giving relief after a disaster to also preparing for and reducing risk before a disaster strikes.
The National GLOF Risk Mitigation Programme is run by the NDMA, the body set up under this Act. The article's call for a national GLOF database and better Centre-state-district coordination matches the Act's three-level structure and the national and state disaster databases required by the 2025 amendment.
The Teesta River Water Dispute
The Teesta is a Himalayan river that starts at Tso Lhamo lake (about 5,280 metres) in North Sikkim, flows through Sikkim and West Bengal, and enters Bangladesh, where it joins the Brahmaputra (called the Jamuna there). It is about 414 km long. India and Bangladesh have long disagreed over how to share its water in the dry season. The river's upper basin in Sikkim also has many glacial lakes and hydropower projects, which links it to GLOF risk.
The 2023 GLOF ran down the Teesta valley and destroyed its biggest dam. This shows that GLOF risk in the upper Teesta is not only a Sikkim problem; it affects power, water and people all the way downstream.
- South Lhonak GLOF (4 October 2023): 55 dead, 74 missing, 7,025 displaced, about 80,000 affected in about 100 villages; damage and losses about ₹1,480 crore
- Global GLOFs 1900–2020: 609 events, over 13,000 deaths; frequency rose from 5.2 a year (1981–90) to 15.2 a year (2011–20)
- Countries with most GLOFs: Peru (117), China (112), Chile (74)
- HKH region: about 9,600 glacial lakes covering about 1,088 sq km; 333 GLOFs between 1833 and 2024
- India: 60 GLOF events and 6,119 deaths (1833–2024), the highest toll in the HKH
- Pakistan: 149 events, 1,991 deaths; China: 202 events, 617 deaths; Nepal: 57 events, 36 deaths
- NRSC inventory (2023): 28,043 glacial lakes larger than 0.25 hectares
- CWC monitoring (June 2025): 2,485 glacial lakes and 358 water bodies; glacial lake area rose about 2.1% between 2011 and June 2025
- National GLOF Risk Mitigation Programme: ₹150 crore; Sikkim, Himachal Pradesh, Uttarakhand, Arunachal Pradesh
- NDMA Guidelines on Management of GLOFs: October 2020