Satellite monitoring shows large expansion in 27 per cent identified glacial lakes in Himalayas: ISRO

New Delhi, April 22

More than 27 per cent of the identified glacial lakes in the Himalayas have notably expanded since 1984 and 130 of those are in India, ISRO said on Monday.

In a statement, the space agency said long-term satellite imagery covering the catchments of Indian Himalayan river basins from 1984 to 2023 indicates significant changes in glacial lakes.

“Of the 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes have notably expanded since 1984,” it said.

Indian Space Research Organisation (ISRO) said 601 of the 676 lakes have expanded more than twice while 10 lakes have grown between 1.5 to two times and 65 lakes 1.5 times.

It said 130 of the 676 lakes are situated within India, with 65, seven, and 58 located in the Indus, Ganga and the Brahmaputra river basins, respectively.

An elevation-based analysis revealed that 314 lakes are located in the 4,000-5,000-metre range and 296 above 5,000 metres.

The glacial lakes are categorised based on their formation process into four broad categories — moraine-dammed (water dammed by moraine), ice-dammed (water dammed by ice), erosion (water dammed in depressions formed by erosion), and other glacial lakes.

Among the 676 expanding lakes, the majority are moraine-dammed (307), followed by erosion (265), other (96), and ice-dammed (eight) glacial lakes.

ISRO highlighted long-term changes in the Ghepang Ghat glacial lake (in the Indus basin) at an elevation of 4,068 metre in Himachal Pradesh, showing a 178 per cent increase in size from 36.49 hectares to 101.30 hectares between 1989 and 2022. The rate of increase is about 1.96 hectares per year.

In October, at least 40 people were killed and 76 went missing in Sikkim after the South Lhonak Lake — a glacial lake situated in the state’s northwest at 17,000 feet — burst due to incessant rains.

The Himalayas, often referred to as the Third Pole because of the extensive glaciers and snow cover, are highly sensitive to changes in the global climate — both in terms of their physical characteristics and their societal impacts.

Research conducted worldwide has consistently shown that glaciers across the globe have been experiencing unprecedented rates of retreat and thinning due to human-caused climate change.

This retreat leads 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, are known as glacial lakes and play a crucial role as freshwater sources for rivers in the Himalayan region.

However, these also pose significant risks such as Glacial Lake Outburst Floods (GLOFs), which can have devastating consequences for communities downstream.

GLOFs occur when glacial lakes release large volumes of meltwater due to the failure of natural dams, such as those made of moraine or ice, resulting in sudden and severe flooding downstream. These dam failures can be triggered by various factors, including avalanches of ice or rock, extreme weather events, and other environmental factors.

Monitoring and studying the occurrence and expansion of glacial lakes in the Himalayan region is challenging due to inaccessible and rugged terrain.

Satellite remote sensing technology proves to be an excellent tool for inventory and monitoring due to its wide coverage and revisit capability.

Assessing long-term changes in glacial lakes is crucial for understanding glacier retreat rates, assessing GLOF risks, and gaining insights into climate change impacts, ISRO said.