ISRO tracks notable expansion of glacial lakes in Indian Himalayas

Bengaluru: Satellite images of catchments of Indian Himalayan river basins over the past 40 years have indicated significant expansion of glacial lakes, the Indian Space Research Organisation (ISRO) said on Monday.

A monitoring of the catchments between 1984 and 2023 revealed that of the 2,431 glacial lakes larger than 10 hectares, identified during 2016-17, 676 have notably expanded since 1984; 130 of these lakes are situated within India -- 65, 7, and 58, located in the Indus, Ganga, and Brahmaputra river basins, respectively.

Among the 676 expanding lakes, 307 are moraine-dammed, or water dammed by moraine (debris left by moving glaciers). The rest of the lakes are water dammed in depressions formed by erosion (265), formed by ice (eight) and other causes (96).

Citing an elevation-based analysis, the space agency said 314 lakes were located in the 4,000 to 5,000 m range and 296 lakes were located above 5,000 m.

Glacier retreat, flood risk

Glaciers are recording extremely high rates of retreat and thinning, leading to the formation of new lakes and the enlargement of existing ones in the Himalayan region. These bodies of water created by the melting of glaciers -- or glacial lakes -- are freshwater sources for rivers in the region. They, however, also pose threats to downstream communities in the form of Glacial Lake Outburst Floods (GLOFs).

These floods occur when the glacial lakes release large volumes of meltwater due to the failure of natural dams, caused by avalanches or extreme weather events.

Long-term changes in the Ghepang Ghat glacial lake in the Indus River Basin, located at an elevation of 4,068 m in Himachal Pradesh, revealed a 178% increase in size -- from 36.49 to 101.30 hectares between 1989 and 2022, an increase of about 1.96 hectares per year.

Studying long-term changes in glacial lakes helps in understanding glacier retreat rates, assessing GLOF risks, and developing climate action strategies for glacial environments, Isro said. Satellite remote sensing has emerged as effective in overcoming geographical limitations for these studies.

• 130 of 676 expanding glacial lakes are in India

• 601 lakes (89 per cent) expanded more than twice

• 296 lakes located above 5,000 m

• Ghepang Ghat lake in HP expanded 1.96 hectares per year