Why in News
🗞️ Why in News A June 2026 satellite study found that four of five glacial lakes in the Mago Chu basin near Tawang, Arunachal Pradesh, are expanding. The largest, Sanhapo Lake, grew from 55.87 hectares in 2016 to 88.81 hectares by June 2026, sharpening concerns about Glacial Lake Outburst Floods (GLOFs) in the eastern Himalaya.
The findings, based on satellite analysis by a private geospatial firm, add to mounting evidence that a warming climate is reshaping the Himalayan cryosphere and creating new disaster risks downstream.
What is a GLOF?
A Glacial Lake Outburst Flood (GLOF) is the sudden release of water from a glacial lake. Glacial lakes form when meltwater collects behind a natural dam, often a loose pile of glacial debris called a moraine. When this moraine dam fails, whether from overtopping, ice avalanche, earthquake or simple erosion, a massive volume of water and debris surges downstream with little warning.
| Element | Description |
|---|---|
| Glacial lake | Meltwater body dammed by moraine or ice |
| Trigger | Avalanche, landslide, earthquake, overtopping |
| Hazard | Sudden, high-energy flood with debris |
| Reach | Can devastate valleys tens of kilometres downstream |
The Tawang Findings
| Lake / Parameter | Detail |
|---|---|
| Basin | Mago Chu basin, Tawang, Arunachal Pradesh |
| Lakes expanding | 4 of 5 studied |
| Sanhapo Lake (2016) | 55.87 hectares |
| Sanhapo Lake (June 2026) | 88.81 hectares |
The expansion is driven by accelerated glacial melt as temperatures rise. Larger lakes mean larger potential flood volumes and greater pressure on the natural dams holding them.
Arunachal: India’s GLOF Hotspot
According to the Central Water Commission (CWC), Arunachal Pradesh has 197 expanding glacial lakes, the highest in India. The state’s steep terrain, seismic activity (it lies in a high earthquake zone) and dense river network make it especially vulnerable.
Why the Himalaya is Warming Faster
The Himalaya is part of the “Third Pole”, holding the largest store of ice outside the polar regions. It is warming faster than the global average, a phenomenon linked to elevation-dependent warming. This accelerates glacier retreat, increases meltwater, and multiplies the number and size of glacial lakes.
The South Lhonak Precedent
The risk is not theoretical. In October 2023, the South Lhonak Lake GLOF in Sikkim breached the Teesta III dam at Chungthang, causing catastrophic downstream flooding and loss of life. It remains the most prominent recent reminder of GLOF danger in the Indian Himalaya and a template for what unmonitored lakes can unleash.
Institutional and Policy Response
| Body | Role |
|---|---|
| National Disaster Management Authority (NDMA) | GLOF risk guidelines, mitigation programme |
| Central Water Commission (CWC) | Monitoring and inventory of glacial lakes |
| State disaster authorities | Early warning, evacuation planning |
The NDMA has been running a national GLOF risk-reduction effort, including lake-level monitoring, automated early-warning systems, and controlled lowering of high-risk lakes.
Analysis and Way Forward
- Continuous monitoring: Combine satellite surveillance with on-ground sensors for high-risk lakes.
- Early-warning systems: Install and maintain automated alarms in vulnerable valleys.
- Risk-informed development: Avoid siting critical infrastructure (dams, settlements) in GLOF flood paths without safeguards.
- Climate action: Address the root cause, accelerated warming, through mitigation while building resilience.
UPSC Relevance
- GS Paper 1 (Geography): Himalayan geomorphology, glaciers, moraine-dammed lakes and the cryosphere.
- GS Paper 3 (Environment / Disaster Management): Climate change impacts, GLOF risk and disaster mitigation.
- Prelims: GLOF definition, Mago Chu basin, Arunachal having 197 expanding lakes (highest), South Lhonak 2023.
- Mains: “Glacial Lake Outburst Floods are an emerging climate-linked disaster in the Himalaya. Discuss causes and mitigation.”
Facts Corner
📌 Facts Corner — Knowledgepedia
- GLOF: Glacial Lake Outburst Flood, the sudden release of water from a glacial lake.
- Tawang study: 4 of 5 lakes in the Mago Chu basin expanding; Sanhapo Lake grew from 55.87 ha (2016) to 88.81 ha (June 2026).
- Arunachal: 197 expanding glacial lakes per the CWC, the highest in India.
- Precedent: South Lhonak Lake GLOF, Sikkim, October 2023.
- Key bodies: NDMA (mitigation) and Central Water Commission (monitoring).
Sources: National Disaster Management Authority, Central Water Commission, Down To Earth
Source: Tawang Glacial Lakes and GLOF Risk in the Himalaya — Ujiyari.com | Free UPSC & State PCS Current Affairs
