Centre monitoring 2,485 Himalayan glacial lakes; 56 classified as 'very high risk'
The Centre reported that it is monitoring approximately 2,485 glacial lakes and water bodies across the Himalayan region using satellite remote sensing. [Unverified — exact total lake count]
Of these, 56 have been classified as "very high risk" for Glacial Lake Outburst Floods (GLOFs).
The classification and monitoring effort follows enhanced satellite surveillance and expeditions to high-risk lakes by central agencies after past GLOF disasters.
The monitoring feeds into early warning system deployment and mitigation planning in Himalayan states.
Glacial Lake Outburst Flood (GLOF) — Definition and Mechanism
A GLOF occurs when a lake formed by glacial meltwater — often dammed by unstable moraine, ice, or a landslide-blocked valley — breaches suddenly, releasing a large volume of water and debris downstream with little warning. Climate warming is accelerating Himalayan glacier retreat, increasing the number and size of such lakes and, consequently, GLOF risk.
Key Details
- The Himalayan region hosts an estimated 7,500+ glacial lakes across the Indus, Ganga, and Brahmaputra river basins
- The 2023 South Lhonak Lake GLOF in North Sikkim (4 October 2023) — triggered by a landslide-induced wave — caused the collapse of the Teesta-III hydropower dam and killed over 50 people, becoming the reference disaster for India's current GLOF policy push
- GLOF risk is assessed on parameters including lake area/volume growth, moraine dam stability, slope angle, and seismicity of the surrounding terrain
- The Central Water Commission (CWC), under the Ministry of Jal Shakti, monitors glacial lakes/water bodies above 10 hectares using high-resolution satellite (Sentinel) data
The 56 "very high risk" lakes represent the subset identified for priority intervention (expeditions, bathymetric surveys, early warning systems) out of the much larger inventory of monitored Himalayan lakes, directly following the lessons of the 2023 Sikkim disaster.
Institutional Framework for GLOF Risk Management
GLOF disaster management in India involves multiple central agencies: the National Disaster Management Authority (NDMA) coordinates risk assessment and early warning deployment; the Central Water Commission (CWC) monitors lake area changes via satellite; and state disaster management authorities implement local mitigation. Post-2023, the CWC made GLOF studies mandatory for all new hydropower projects with glacial lakes in their catchment.
Key Details
- NDMA constituted a Committee on Disaster Risk Reduction (CoDRR) involving representatives from Himalayan states/UTs to identify and prioritize high-risk lakes for expeditions and mitigation
- After the Teesta-III dam collapse (2023), CWC mandated a review of design flood capacity for all existing and under-construction dams vulnerable to GLOFs
- NDMA has planned to install early warning systems (automatic weather stations, lake-level sensors, siren-based alert systems) at most of the very-high-risk lakes
- National Action Plan on Climate Change's National Mission for Sustaining the Himalayan Ecosystem (NMSHE) also funds glacial and glacial-lake research
The Centre's classification exercise is the data foundation for NDMA's early warning system rollout and for CWC's mandatory dam-safety reviews in glacial lake catchments — both direct policy responses to the 2023 Sikkim GLOF.
Sikkim and the Eastern Himalaya — Geographic Vulnerability
Sikkim and other parts of the Eastern Himalaya (Arunachal Pradesh, Himachal Pradesh, Uttarakhand, Ladakh) are disproportionately vulnerable to GLOFs due to a high concentration of glacial lakes fed by retreating glaciers in steep, seismically active terrain, compounded by hydropower infrastructure built in these high-risk river valleys.
Key Details
- Sikkim alone accounts for roughly one-tenth of the Himalayan region's glacial lakes
- Key GLOF-prone river basins: Teesta (Sikkim), Indus and its tributaries (Ladakh), Brahmaputra tributaries (Arunachal Pradesh)
- The Ladakh region has also recorded rapidly expanding glacial lakes assessed for GLOF risk using hydrodynamic modeling
- State Disaster Management Authorities (e.g., Sikkim SDMA) conduct Post-Disaster Needs Assessments (PDNA) to guide reconstruction and mitigation funding
The "very high risk" classification is concentrated in these geographically vulnerable Himalayan states, informing where central mitigation funding and early warning infrastructure will be prioritized.
- Glacial lakes monitored by the Centre: approximately 2,485 [Unverified — exact figure]; broader Himalayan inventory estimated at 7,500+ glacial lakes
- Lakes classified "very high risk" for GLOF: 56
- Reference disaster: South Lhonak Lake GLOF, Sikkim, 4 October 2023 — over 50 deaths, Teesta-III dam destroyed
- Nodal agencies: National Disaster Management Authority (NDMA) and Central Water Commission (CWC), Ministry of Jal Shakti
- Post-2023 policy change: GLOF studies made mandatory for new dams with glacial lake catchments; design flood review mandated for existing/under-construction dams