Nepal plans to drain four glacial lakes after deadly floods

Disaster Management · 3 October 2026 · Based on The Hindu (original report)

2-minute summary

Nepal has announced a high-stakes, six-year project to drain four highly dangerous glacial lakes—Thulagi, Lower Barun, Lumding Tsho, and Hongu II—located at altitudes between 4,050 and 5,483 meters. This initiative aims to mitigate the risk of Glacial Lake Outburst Floods (GLOFs) following a devastating glacier collapse and flash flood in August 2026 that killed over 1,400 people and left 5,000 missing. The $50-million project will be co-funded by the Green Climate Fund (GCF), the United Nations Development Programme (UNDP), and the Nepalese government. It involves constructing gated structures to release water in a regulated manner, installing automated sensors, and establishing early warning systems. As climate change accelerates Himalayan glacial melt, unstable moraine-dammed lakes pose an existential threat to downstream communities and infrastructure across South Asia, highlighting the urgent need for transboundary climate adaptation and disaster risk reduction.

Why it's in the news

Nepal has launched a $50-million initiative to drain four high-risk glacial lakes to prevent Glacial Lake Outburst Floods (GLOFs). This decision follows a catastrophic glacier collapse in August 2026 that caused over 1,400 deaths and highlighted the severe climate vulnerabilities of the Hindu Kush Himalayan region.

Facts to remember

• Nepal plans to drain four high-altitude glacial lakes: Thulagi, Lower Barun, Lumding Tsho, and Hongu II, located at elevations between 4,050 m and 5,483 m.
• The $50-million GLOF mitigation project is co-funded by the Green Climate Fund (GCF), the United Nations Development Programme (UNDP), and the Government of Nepal.
• Nepal has experienced approximately 26 Glacial Lake Outburst Flood (GLOF) events over the past four decades.
• Nepal previously successfully lowered the water levels of Tsho Rolpa (in 2000) and Imja Lake (in 2016) to mitigate GLOF risks.
• The International Centre for Integrated Mountain Development (ICIMOD) is an intergovernmental regional organization focused on the Hindu Kush Himalaya region, headquartered in Kathmandu, Nepal.

Background and context

The Hindu Kush Himalaya (HKH) region, often referred to as the 'Third Pole', holds the largest reserve of ice outside the polar regions. Due to rising global temperatures, Himalayan glaciers are retreating rapidly, leaving behind vast, unstable lakes dammed only by loose moraine (rock and soil debris). When these natural dams breach—triggered by earthquakes, avalanches, or extreme precipitation—they cause catastrophic Glacial Lake Outburst Floods (GLOFs). The vulnerability of the region was starkly demonstrated by the August 2026 floods in Nepal, which destroyed critical infrastructure, including a dozen hydroelectric plants, roads, and bridges. Because these river basins are transboundary, a GLOF in Nepal or Tibet poses a direct, downstream flood threat to Indian states like Bihar, West Bengal, and Sikkim, making glacial lake management a critical regional security and ecological issue.

Constitutional provisions

• Article 48A — Directs the Indian State to protect and improve the environment and safeguard forests and wildlife, highlighting India's constitutional commitment to ecological security.
• Article 51A(g) — Imposes a fundamental duty on every citizen of India to protect and improve the natural environment, including forests, lakes, rivers, and wildlife.

Committees and reports

• NDMA Guidelines on Management of Glacial Lake Outburst Floods (GLOFs) — Provides a comprehensive national framework in India for identifying high-risk glacial lakes, monitoring them using space technology, and implementing structural and non-structural mitigation measures.
• ICIMOD & UNDP Inventory of Glacial Lakes — Identified and mapped the most dangerous glacial lakes in the Hindu Kush Himalaya region, providing the scientific basis for Nepal's current draining project.

Government schemes

• National Mission for Sustaining the Himalayan Ecosystem (NMSHE) — One of the eight missions under India's National Action Plan on Climate Change (NAPCC), focused on monitoring glacier health and forest cover in the Indian Himalayan Region.

International organisations

• Green Climate Fund (GCF) — A global fund created under the UNFCCC to support developing countries in responding to climate change; it is a primary co-funder of Nepal's $50-million GLOF mitigation project.
• International Centre for Integrated Mountain Development (ICIMOD) — An intergovernmental learning and knowledge-sharing centre serving eight regional member countries of the Hindu Kush Himalayas, crucial for transboundary disaster data sharing.

Mains practice: Explain the phenomenon of Glacial Lake Outburst Floods (GLOFs). Discuss the ecological and socioeconomic vulnerabilities of the Hindu Kush Himalayan region to GLOFs, and suggest effective mitigation strategies.

Glacial Lake Outburst Floods (GLOFs) occur when unstable natural dams impounding glacial meltwater—composed of loose moraine, rock, or ice—suddenly breach. This releases massive volumes of water and debris downstream with immense destructive force. The catastrophic glacier collapse in Nepal in August 2026, which resulted in over 1,400 deaths, underscores the escalating threat of GLOFs driven by rapid glacial retreat.

• **Ecological Vulnerabilities:** The Hindu Kush Himalaya (HKH) region is seismically active (falling under Seismic Zones IV and V in India), making moraine dams highly susceptible to earthquake-induced failures. Unpredictable extreme weather events, such as cloudbursts, accelerate meltwater accumulation, compounding the risk of sudden breaches.

• **Socioeconomic Vulnerabilities:** Downstream river valleys host dense agrarian populations and critical infrastructure. The August 2026 floods devastated a dozen hydroelectric plants, roads, and bridges in Nepal. Furthermore, because rivers like the Kosi and Gandak are transboundary, GLOFs originating in Nepal or Tibet pose direct threats to downstream states in India, such as Bihar and West Bengal, risking lives, agriculture, and regional food security.

**Mitigation Strategies:**

• **Structural Engineering Interventions:** Implementing controlled lake lowering through gated channels, siphoning, or tunneling, as seen in Nepal's $50-million project to drain Thulagi and Lower Barun lakes.

• **Non-Structural Early Warning Systems (EWS):** Installing automated water-level sensors and satellite-based synthetic aperture radar (SAR) to monitor lake expansion, aligned with India's National Mission for Sustaining the Himalayan Ecosystem (NMSHE).

• **Hazard Mapping and Zoning:** Utilizing GIS-based risk mapping to restrict infrastructure development in high-risk downstream zones, as recommended by the NDMA Guidelines (2020).

• **Transboundary Cooperation:** Establishing real-time data-sharing protocols and joint monitoring frameworks between India, Nepal, Bhutan, and China under the aegis of regional bodies like ICIMOD.

In conclusion, addressing GLOF risks is vital to achieving SDG 13 (Climate Action) and fulfilling the Sendai Framework for Disaster Risk Reduction, ensuring the long-term ecological and economic security of the Himalayan region.

Prelims practice questions

Q1. Consider the following statements regarding Glacial Lake Outburst Floods (GLOFs) and mitigation efforts in the Hindu Kush Himalayas: 1. Thulagi, Lower Barun, and Imja are examples of potentially dangerous glacial lakes located in Nepal. 2. The International Centre for Integrated Mountain Development (ICIMOD) is a regional intergovernmental organization headquartered in New Delhi. 3. Controlled draining of glacial lakes to lower water levels is a recognized structural mitigation strategy for GLOFs. How many of the above statements are correct?

1. Only one
2. Only two
3. All three
4. None

Answer: B. Statement 1 is correct: Thulagi, Lower Barun, and Imja are all located in Nepal and have been identified as high-risk lakes. Statement 2 is incorrect: ICIMOD is headquartered in Kathmandu, Nepal, not New Delhi. Statement 3 is correct: Controlled draining using gated structures or siphoning is a primary structural mitigation strategy to reduce hydrostatic pressure on moraine dams.

Q2. Consider the following statements: Statement-I: Glacial Lake Outburst Floods (GLOFs) are expected to increase in frequency and intensity across the Hindu Kush Himalayan region in the coming decades. Statement-II: Rising global temperatures lead to rapid glacial retreat, resulting in the formation of larger and more unstable moraine-dammed lakes. Which one of the following is correct in respect of the above statements?

1. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
2. Both Statement-I and Statement-II are correct but Statement-II does not explain Statement-I
3. Statement-I is correct but Statement-II is incorrect
4. Statement-I is incorrect but Statement-II is correct

Answer: A. Both statements are correct. Rising global temperatures cause glaciers to melt and retreat rapidly. This meltwater accumulates behind weak, natural dams made of loose rock and soil (moraines). Because these dams are unstable, the risk of sudden failure and subsequent GLOFs increases, directly explaining the rising frequency and intensity of these disasters.

Q3. The 'Green Climate Fund' (GCF), which is co-funding Nepal's $50-million glacial lake draining project, was established as a financial mechanism under which of the following international frameworks?

1. United Nations Framework Convention on Climate Change (UNFCCC)
2. Basel Convention on Transboundary Movements of Hazardous Wastes
3. Convention on Biological Diversity (CBD)
4. United Nations Convention to Combat Desertification (UNCCD)

Answer: A. The Green Climate Fund (GCF) was established as a financial mechanism under the United Nations Framework Convention on Climate Change (UNFCCC) at COP16 in Cancun, Mexico, in 2010, to assist developing countries in adaptation and mitigation practices.

Revision flashcards

• What is a Glacial Lake Outburst Flood (GLOF)? A sudden release of water from a glacial lake dammed by unstable moraine (loose rock and debris), often triggered by avalanches, earthquakes, or extreme rainfall.
• Where is the headquarters of the International Centre for Integrated Mountain Development (ICIMOD), and which region does it serve? Headquartered in Kathmandu, Nepal. It serves the Hindu Kush Himalaya (HKH) region, comprising eight regional member countries including India.
• Which four high-risk glacial lakes did Nepal announce plans to drain over a six-year period starting in the fiscal year ending mid-2027? Thulagi, Lower Barun, Lumding Tsho, and Hongu II.
• Which international financial mechanism, established under the UNFCCC, was announced in October 2026 as a co-funder of Nepal's $50-million glacial lake draining project? The Green Climate Fund (GCF), alongside the UNDP and the Government of Nepal.
• Why are moraine-dammed glacial lakes highly susceptible to sudden breaches compared to ice-dammed lakes? Moraines consist of loose, unconsolidated debris and rocks that lack structural cohesion, making them easily eroded or breached by hydrostatic pressure or trigger events.