Four glacial lakes in Arunachal have expanded in a decade: study, Pg10

Key Highlights:

• A satellite-based assessment in Arunachal Pradesh's Tawang district revealed that four out of five glacial lakes in the Mago Chu basin have expanded over the last decade.
• Sanhapo Lake showed the most significant growth, increasing from 78.07 hectares in 2019 to 88.81 hectares by mid-June 2026.
• These five lakes are classified as "high-risk" or "very high-risk" by the National Disaster Management Authority (NDMA) due to potential Glacial Lake Outburst Floods (GLOFs).
• The assessment, conducted by Suhora Technologies, utilized imagery from ICEYE, PlanetScope, and LISS-IV satellites.
• The findings underscore concerns over glacial hazards in the Eastern Himalaya, following the October 2023 South Lhonak Lake disaster in Sikkim.

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Detailed Insights:

• The expansion of glacial lakes is attributed to the general trend of glacial retreat and increased meltwater storage, primarily driven by rising temperatures.
• While lake expansion does not directly indicate an imminent flood event, it highlights the critical need for continuous monitoring and further assessment of these unstable lakes.
• The NDMA has identified 189 high-risk glacial lakes for monitoring and mitigation under the National Glacial Lake Outburst Floods Risk Mitigation Programme.
• The 2023 South Lhonak Lake GLOF in Sikkim, which destroyed the Chungthang hydropower dam and caused casualties, intensified focus on Himalayan glacial hazards.
• Experts emphasize that the stability of moraine dams and other factors like landslides, avalanches, or rockfalls into the lake are crucial in determining the actual risk of a GLOF.
• Satellite observations are increasingly vital for monitoring remote mountain regions where field access is challenging, aiding in tracking changes in glacial lake extent.
• Translating scientific assessments into practical risk reduction measures, including early-warning systems and hazard modeling, remains a significant challenge.

Key Concepts Involved:

• Glacial Lake Outburst Flood (GLOF): A sudden release of a large volume of water from a glacial lake, typically caused by the failure of its natural dam (often a moraine dam).
• National Disaster Management Authority (NDMA): India's apex statutory body for disaster management, responsible for policies, plans, and guidelines under the Disaster Management Act, 2005.
• Moraine Dam: A natural dam formed by unconsolidated rock and sediment debris deposited by a glacier, which can impound meltwater to form a glacial lake.
• Glacial Retreat: The process where a glacier shrinks or recedes due to a net loss of ice, primarily caused by rising global temperatures and changes in precipitation patterns.