Growing Glacial Flood Threat in Arunachal Pradesh: GLOF Risks and Mitigation Measures

20 Jun 2026

Subject: GS 3: Environment

Context: A new satellite study reveals that four out of five high-risk glacial lakes in the Tawang district of Arunachal Pradesh have expanded over the last ten years due to glacier melt, increasing the risk of flash floods.

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Key Findings of the Study

Location of Hazard: The study focused on five lakes located in the Mago Chu basin of Tawang, Arunachal Pradesh. These lakes are classified as “high-risk” or “very high-risk” by the National Disaster Management Authority (NDMA).
Sanhapo Lake Growth: This lake showed the fastest growth. Its size increased from 78.07 hectares in 2019 to 88.81 hectares in mid-2026. It is now the highest-priority lake for safety monitoring.
Other Lakes: Two “very high risk” lakes grew by about one hectare, and another lake named Dharkha Tso also expanded slowly. Only one out of the five lakes stayed stable.
Satellites Used: The team tracked changes from 2016 to 2026 using advanced space tools like ICEYE, PlanetScope, and India’s LISS-IV satellites.

Associated Geographical & Science Concepts

Glacial Lake Outburst Flood (GLOF): A GLOF is a sudden, disastrous flood that happens when a natural dam holding back a glacial lake breaks.
Moraine Dams: As glaciers melt and pull back, they leave behind walls of loose rock, ice, and soil called moraines. These moraines act as natural dams to trap meltwater. Because they are made of loose debris, they are unstable and can burst easily.
Trigger Factors: While lake growth indicates instability, a GLOF is usually triggered by other sudden events such as landslides, avalanches, cloudbursts, or rockfalls crashing into the lake and creating giant waves.
Recent Disaster Example: In October 2023, a breach at the South Lhonak Lake in Sikkim triggered a massive flood that destroyed the Chungthang hydropower dam and killed dozens of people.

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Policy Frameworks and Mitigation Initiatives

National GLOF Risk Mitigation Programme: Launched by the NDMA after the Sikkim disaster, this program targets 189 high-risk glacial lakes across the Himalayas for safety actions.
Key Strategies: The program involves setting up early-warning networks, installing automated weather stations, tracking water levels, and using lake-lowering measures (pumping out water) to reduce water pressure on natural dams.
Satellite Tracking: The Central Water Commission (CWC) is currently using space data to monitor more than 900 glacial lakes and water bodies across India.
The Main Challenge: Experts point out that while India has become great at identifying risky lakes using satellite data, the real challenge lies in translating these alerts into quick engineering solutions to protect remote mountain communities.