Four Glacial Lakes in Arunachal Pradesh Expanded Over a Decade: Study
Context
A satellite-based assessment of five glacial lakes in the Mago Chu Basin of Arunachal Pradesh found that four lakes expanded between 2016 and June 2026. The assessment was conducted by Suhora Technologies and is a technical report rather than a peer-reviewed scientific study.
The lakes are situated in Tawang District and have been classified as “High Risk” or “Very High Risk” by the National Disaster Management Authority (NDMA).
The findings indicate a broader trend of glacial retreat and increasing meltwater storage in the Eastern Himalayas.However, an increase in glacial lake size does not necessarily indicate an imminent flood event.
Satellite Monitoring and Methodology
The study compared satellite imagery collected over a decade using the following platforms:
1. ICEYE
- A commercial constellation of Synthetic Aperture Radar (SAR) satellites.
- Provides high-resolution Earth imagery:
- Day and night
- Through cloud cover
- In all weather conditions
2. PlanetScope
- A constellation of optical Earth-observation satellites.
- Captures near-daily images of Earth’s surface.
- Offers high spatial resolution for environmental monitoring.
3. LISS-IV (Linear Imaging Self-Scanning Sensor-IV)
- A high-resolution multispectral camera onboard Indian Remote Sensing satellites.
- Used for:
- Land-use mapping
- Vegetation monitoring
- Water-body assessment
- Natural resource management
Prelims Tip: Remember the names ICEYE, PlanetScope and LISS-IV, as they may be asked in matching-type questions related to remote sensing satellites and sensors.
Key Findings
1. Significant Expansion of Glacial Lakes
Out of five monitored lakes:
- Four lakes expanded between 2016 and 2026.
- One lake remained largely stable during the observation period.
Sanhapo Lake: Highest Concern
Among all the lakes, Sanhapo Lake recorded the most substantial growth.
| Year | Area |
|---|---|
| 2019 | 78.07 hectares |
| June 2026 | 88.81 hectares |
Why is Sanhapo Lake Important?
- Largest increase in area among the monitored lakes.
- Continuous expansion observed in recent years.
- Earlier satellite imagery contained ice cover, creating some uncertainty about historical lake extent.
- Identified as the highest-priority lake for:
- Hazard modelling
- Continuous monitoring
- Early-warning systems
2. Other High-Risk Lakes
- Two lakes categorized as “Very High Risk” by NDMA expanded by nearly one hectare during the decade.
- Dharkha Tso, categorized as “High Risk”, also showed gradual expansion.
Importance of Satellite Monitoring
Monitoring Himalayan glacial lakes through satellites is becoming increasingly important because:
- Many glacial lakes are located in remote and inaccessible regions.
- Ground-based surveys are expensive and difficult.
- Multi-year satellite observations help:
- Track glacial retreat
- Measure lake expansion
- Identify potentially dangerous lakes
- Support disaster preparedness
Special Relevance During Monsoon
Continuous monitoring becomes crucial before and during the monsoon season when:
- Heavy rainfall increases water levels.
- Landslides and avalanches become more frequent.
- Risk of glacial lake outburst floods rises significantly.
Glacial Lake Outburst Floods (GLOFs)
What is a GLOF?
A Glacial Lake Outburst Flood (GLOF) refers to the sudden release of water from a glacial lake, causing destructive downstream flooding.
Causes of GLOFs
GLOFs may occur due to:
- Failure of natural moraine dams
- Avalanches
- Landslides
- Icefalls
- Sudden displacement of lake water
Moraines and Their Role
What are Moraines?
Moraines are ridges of:
- Rock
- Soil
- Sediments
- Glacial debris
deposited by glaciers.
Why are They Important?
- Moraines often act as natural dams holding back glacial lakes.
- As glaciers retreat, more meltwater accumulates behind these fragile barriers.
- This increases the risk of catastrophic dam failure.
Factors Determining GLOF Risk
The probability of a GLOF depends on:
- Stability of moraine dams
- Landslides
- Avalanches
- Rockfalls
- Volume of stored water
- Glacier dynamics
Growing Concerns in the Himalayas
Concerns regarding Himalayan glacial hazards intensified following the 2023 South Lhonak Lake Disaster in Sikkim.
October 2023 GLOF Disaster
A GLOF associated with South Lhonak Lake triggered:
- Massive downstream flooding
- Multiple fatalities
- Destruction of the Chungthang Hydropower Dam
- Severe damage to infrastructure and livelihoods
The disaster highlighted the growing vulnerability of Himalayan regions to climate-induced glacial hazards.
Way Forward
India’s capability to identify potentially dangerous glacial lakes has improved significantly through:
- Remote sensing technologies
- Satellite monitoring
- Hazard modelling
- Risk assessment frameworks
However, the major challenge lies in translating scientific assessments into:
- Effective early-warning systems
- Community preparedness measures
- Disaster-resilient infrastructure
- Timely evacuation mechanisms
Conclusion
The expansion of four glacial lakes in Arunachal Pradesh reflects the broader pattern of glacial retreat and increasing meltwater accumulation in the Himalayas. While lake growth does not automatically lead to a flood, it serves as an important warning signal. Strengthening satellite-based monitoring, hazard assessment, and early-warning systems will be critical to reducing the risks posed by future Glacial Lake Outburst Floods (GLOFs) in India’s Himalayan region.
