Arunachal Pradesh’s Expanding Glacial Lakes

Arunachal Pradesh has identified 32 high-risk glacial lakes requiring active mitigation against Glacial Lake Outburst Floods. The concern has gained importance as satellite studies show rapid expansion of several high-altitude lakes, particularly in the Mago Chu basin of Tawang district.

A 2026 satellite assessment found that four of five potentially dangerous lakes in the Mago Chu basin expanded between 2016 and 2026. Sanhapo Lake expanded from about 55.87 hectares in 2016 to 88.81 hectares in June 2026, making it a major monitoring concern.

Why is this a serious concern?

As glaciers retreat, meltwater can accumulate behind moraine dams and form glacial lakes. If the natural dam suddenly fails because of an ice or rock avalanche, excessive water pressure or other triggers, a huge volume of water can rush downstream as a Glacial Lake Outburst Flood.

For Arunachal Pradesh, the danger extends beyond the mountains because rivers originating in these high-altitude areas eventually enter the plains.

• The Tawang Chu, known as the Jia-Bharali in Assam, can carry such downstream impacts into Assam.
• The Dibang river system is another important high-altitude basin requiring monitoring.
• Transboundary river systems such as the Punatsang Chhu and Kuri Chu in Bhutan are also important because their downstream systems are connected with Assam’s river network.

Therefore, GLOF is not merely a mountain hazard; it can become a downstream disaster affecting settlements, roads, bridges, hydropower projects and agriculture.

Scientific Evidence and Monitoring

Recent research confirms that Arunachal’s high-altitude lakes are changing significantly. A 2026 study using multi-temporal satellite data found substantial changes in lake numbers and areas and highlighted lake expansion rate and proximity to glaciers as important factors in GLOF-risk assessment.

Monitoring should combine:

• High-resolution satellite imagery should be used to track changes in lake size, glacier retreat and surrounding terrain.
• Interferometric Synthetic Aperture Radar can detect subtle ground and glacier movements and can operate even through clouds and darkness.
• Bathymetric surveys can estimate lake depth and water volume, helping authorities understand the potential magnitude of an outburst.
• Automated weather stations and water-level sensors can provide real-time information on temperature, rainfall and changing lake levels.

Institutional and Policy Framework

The Arunachal Pradesh State Disaster Management Authority is strengthening technical preparedness through training in bathymetry surveys for high-risk glacial lakes. This work is being undertaken under the National Glacial Lake Outburst Flood Risk Mitigation Programme.

The national programme covers Arunachal Pradesh, Himachal Pradesh, Sikkim and Uttarakhand with an approved outlay of ₹150 crore, including a central share of ₹135 crore. Arunachal Pradesh has an approved project outlay of ₹45 crore.

Way Forward

Arunachal needs to move from post-disaster response to anticipatory risk management. High-risk lakes should receive continuous monitoring, while vulnerable downstream villages and infrastructure should have early-warning systems, evacuation plans and community-level disaster drills.

Since Himalayan rivers cross political boundaries, India-Bhutan coordination and real-time hydrological data sharing are equally important.

Exam Hook – Key Takeaway

Mains: The growing threat of Glacial Lake Outburst Floods in the Eastern Himalayas requires an integrated approach involving climate monitoring, satellite technology, early warning and transboundary cooperation. Discuss.

One-line Wrap

The expanding glacial lakes of Arunachal Pradesh are a warning that climate change can transform a distant mountain process into a major downstream disaster for the Eastern Himalayas and Assam.