89% Expanding Glacial Lakes In Himalayas Grew More Than Twice In 38 Years: ISRO

At least 89 per cent of 2,431 glacial lakes in the Himalayas that were identified in 2016-17 have notably expanded since 1984, the Indian Space Research Organisation (ISRO) said in a report today.

The results of the ISRO analysis is worrying as expanding glacial lakes due to warming can lead to cascading consequences in the lower regions, say experts. Satellite data archives spanning the past three to four decades provide valuable insights into changes occurring in glaciated environments, ISRO said.

Long-term satellite imagery covering the catchments of Indian Himalayan river basins from 1984 to 2023 indicates significant changes in glacial lakes, ISRO said in the report.

The ISRO report said 601 glacial lakes, or 89 per cent, have expanded more than twice, and 10 lakes have grown between 1.5 times and double their size. Sixty-five lakes have expanded 1.5 times.

Of the 2,431 glacial lakes larger than 10 hectares, 676 have significantly expanded, and at least 130 of these lakes are in India - 65 (Indus river basin), 7 (Ganga river basin), and 58 (Brahmaputra river basin).

Elevation-based analysis shows 314 lakes are located in the 4,000 to 5,000 metres range, and 296 lakes are above 5,000 metres elevation, ISRO said in the report 'Satellite Insights: Expanding Glacial Lakes in the Indian Himalayas' released today.

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

The satellite-derived long-term change analyses also provide valuable insights for understanding glacial lake dynamics, which are essential for assessing environmental impacts and developing strategies for glacial lake outburst flood (GLOF) risk management and climate change adaptation in glacial environments, ISRO said.

The study faced challenges due to the inaccessible and rugged terrain, the ISRO said. Satellite remote sensing technology, however, helped as an excellent tool for inventory and monitoring due to its wide coverage and revisit capability, the space agency said.

The Himalayan mountains are often referred to as the "Third Pole" because of their extensive glaciers and snow cover, and 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 since the onset of the Industrial Revolution in the 18th century, ISRO said in the report.

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, they also pose significant risks, such as 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.