Four Glacial Lakes in Arunachal have expanded in a decade

Context: A satellite-based assessment of glacial lakes in Arunachal Pradesh’s Tawang district found that four out of five high-risk lakes have expanded between 2016 and 2026, raising concerns over Glacial Lake Outburst Floods (GLOFs) in the Eastern Himalayas.

Prelims : 

• The study was conducted by Suhora Technologies, a geospatial intelligence firm.
• Assessment covered five glacial lakes in the Mago Chu Basin of Tawang district, Arunachal Pradesh.
• The lakes were previously classified as “High-Risk” or “Very High-Risk” by the National Disaster Management Authority (NDMA).
• Satellite imagery from ICEYE, PlanetScope, and LISS-IV was used for analysis.
• Comparison of lake extents was carried out between 2016 and June 2026.
• Four out of five lakes showed expansion, indicating continued glacier retreat and increased meltwater accumulation.

Key Findings

• Sanhapo Lake recorded the most significant growth.
  • The area increased from 78.07 hectares (2019) to 88.81 hectares (2026).
  • Expansion of nearly 10 hectares.
• Two other lakes categorized as “Very High Risk” expanded by around one hectare each.
• Another high-risk lake also showed gradual expansion.
• One lake remained largely stable during the observation period.

About Glacial Lake Outburst Floods (GLOFs)

• GLOFs occur when water stored in glacial lakes is suddenly released.
• They are often triggered by:
  • Failure of natural moraine dams.
  • Avalanches or landslides entering the lake.
  • Ice or rockfalls causing displacement waves.
• GLOFs can generate devastating downstream floods.

Important Concepts

• Moraine: Accumulation of rock debris and sediments deposited by glaciers.
• Moraine-Dammed Lakes: Lakes impounded behind glacial debris deposits.
• Retreating glaciers can increase water accumulation in such lakes, potentially elevating risk levels.

Key Observations by Experts

• Expansion of a glacial lake does not automatically indicate an imminent disaster.
• Lake size alone is not sufficient to determine risk.
• Other factors such as:
  • Slope stability,
  • Landslides,
  • Avalanches,
  • Rockfalls,
  • Nature of the moraine dam 

Why It Matters?

• Concerns over Himalayan glacial hazards have intensified after the South Lhonak Lake GLOF in Sikkim (October 2023).
• The flood caused severe damage downstream, including destruction of the Chungthang Hydropower Project and significant loss of life.
• Continuous satellite monitoring is increasingly important because many Himalayan glacial lakes are located in remote and inaccessible terrain.

Mains : 

• Illustrates the impact of climate change and glacier retreat in the Himalayas.
• Highlights the need for:
  • Continuous satellite-based monitoring,
  • Early warning systems,
  • Hazard modelling,
  • Disaster preparedness in mountain regions.
• Demonstrates the growing importance of remote sensing and geospatial technologies in disaster risk reduction.