A groundbreaking study has revealed alarming glacier retreat in the Mago Chu sub-basin of western Arunachal Pradesh, a critical headwater zone of the Brahmaputra river, raising serious concerns about flood risks. Conducted by the Centre for Earth Sciences and Himalayan Studies (CESHS) in collaboration with the National Centre for Polar and Ocean Research (NCPOR), IIT Roorkee, IIT Guwahati, and other institutions, the research shows that glaciers in the basin have lost 28.5% of their area—over 15 square kilometers of ice—between 1988 and 2019.

The study highlights the fragmentation of larger glaciers, particularly on south-west facing slopes, where ice loss has reached nearly 50%. The Equilibrium Line Altitude (ELA), a key measure of glacier health, has risen by approximately 137 meters during this period, indicating a negative mass balance where glaciers are not being replenished.

Tana Tage, Director of CESHS, emphasized the severity of the situation, stating, “Glaciers in the Mago Chu are retreating faster than many parts of the Western Himalaya. Large glaciers are breaking down into smaller, unstable fragments that are more vulnerable to melt and collapse.” This trend threatens not only Arunachal Pradesh but the entire Brahmaputra basin, spanning India, Bhutan, and Bangladesh.

The retreat is exacerbated by a sharp decline in monsoon precipitation, critical for summer-accumulating glaciers. Rainfall in the region has plummeted from 2,100 millimeters in the mid-1980s to less than 1,500 millimeters after 2000, with only 900 millimeters recorded in 2024. With negligible winter snowfall, glaciers are losing their natural recharge system.

This has led to a dramatic expansion of glacial lakes, growing from 15 lakes covering 0.71 square kilometers in 1988 to 29 lakes spanning 2.11 square kilometers by 2017. Four of these lakes are classified as ‘high-risk’ by the National Disaster Management Authority, with some expanding from small depressions to reservoirs larger than 0.8 square kilometers.

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Field investigations underscore the crisis. CESHS researchers recorded nearly one meter of ice loss on the Khangri Glacier last winter, with minimal snow accumulation. Real-time data from an automatic weather station and water level recorder—the first continuous monitoring in this remote region—confirm rapid mass loss. Hydrodynamic models warn that a breach in one of these high-risk lakes could unleash flood waves exceeding 12,000 cubic meters per second, threatening villages like Mago, Thingbu, and Chagzum, as well as hydropower infrastructure.

Tage stressed the need for integrated solutions, noting, “Science alone cannot save lives. We must combine data with community preparedness, evacuation drills, and early warning systems.” He highlighted the importance of local knowledge and resilience, given the centuries-long coexistence of Tawang’s communities with these landscapes. Plans are underway to establish a permanent base camp for long-term cryosphere monitoring, positioning the Mago Chu basin as a critical site for studying global climate change and developing adaptation strategies.

The rapid glacier retreat in Mago Chu serves as a stark warning of the broader impacts of climate change, urging immediate action to safeguard vulnerable communities and ecosystems in the Brahmaputra basin.

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