A study conducted by researchers at the University of Prague has found that glacial lakes in the western Himalayas have expanded by 67% over the past three decades, significantly increasing the risk of catastrophic floods. Using satellite data from 1994 to 2023, scientists analyzed 74 glacial lakes in the Alaknanda River basin, a key source of the Ganges. The total surface area of 24 lakes larger than 0.01 km² grew from 0.97 km² in 1994 to 1.62 km² in 2023, according to the research published in Open Geosciences. This expansion is attributed to the accelerated melting of glaciers driven by climate change.
Study Reveals 67% Expansion of Glacial Lakes in Western Himalayas
57 New Lakes Formed, Totaling 131 in the Region
The study identified 57 new glacial lakes formed between 1994 and 2023, raising the total number of lakes in the Alaknanda basin to 131. Among these, 18 lakes exceeded the 0.01 km² threshold for detailed analysis. Some lakes saw dramatic growth, such as Vasundhara, whose area increased by 261%, and Balbala, which expanded by 119%. Researchers emphasized that the rapid growth of these lakes, combined with unstable geological conditions, heightens the risk of glacial lake outburst floods (GLOFs), where sudden water release can devastate downstream regions.
GLOF Risks Escalate as Lakes Grow in Size and Number
Glacial lake outburst floods (GLOFs) occur when water trapped behind glacial barriers—comprised of ice, rock, or sediment—is abruptly released, often triggering destructive flows of water, mud, and debris. While a recent flood in Nepal in August 2026, which killed over 1,300 people, was not classified as a classic GLOF, it underscored the dangers of unstable high-altitude water bodies. Dr. Aayushi Pandey, a researcher at the University of Prague and co-author of the study, noted that the interplay of extreme rainfall, glacial lake expansion, and seismic activity in the region creates complex risks for downstream communities. Climatic and geological factors are increasingly interacting to amplify flood threats, she said.
Satellite Data Complements Field Studies for Accurate Risk Assessment
While satellite imagery from systems like Landsat and Sentinel-2 has been critical for monitoring glacial lakes, researchers stress that field studies are essential for comprehensive risk evaluation. Satellite data allows scientists to detect new lakes, measure surface area changes, and identify rapidly growing water bodies. However, determining lake depth, sediment stability, and flood pathways requires on-the-ground assessments. Satellite data is invaluable, but it cannot replace fieldwork to assess structural risks and improve flood models, Pandey explained. The study highlights the need for integrated approaches to monitor and mitigate the growing threat of GLOFs in the Himalayas.
Urgent Call for Regional Flood Mitigation Strategies
The findings have prompted calls for enhanced regional cooperation to address flood risks. The expansion of glacial lakes, coupled with climate-driven glacier retreat, poses a growing challenge for communities in the western Himalayas. Researchers emphasize that proactive measures, including early warning systems and infrastructure planning, are necessary to protect vulnerable populations. As the number and size of glacial lakes continue to rise, the study serves as a critical reminder of the urgent need for adaptive strategies to safeguard lives and ecosystems in the region.
