Looming danger of ever-expanding glacial lakes in the Himalayas

ISRO’s latest report suggests that around 28% of the identified Himalayan glacial lakes that are larger than 10 hectares, have expanded since 1984.
HimalayasFile photo | AP

NEW DELHI: Remember the South Lhonak glacial lake outburst floods (GLOF) in Sikkim in October last year that washed away an entire army camp downstream, including personnel, trucks and munitions in a sudden gush of icy water? Monitoring glacial lakes can be daunting at the best of times because of their inaccessibility. But the country’s eye in the sky through the Indian Space Research Organisation (ISRO) has been tracking the glacial lakes in the Himalayas for decades.

ISRO’s latest report suggests that around 28% of the identified Himalayan glacial lakes that are larger than 10 hectares, have expanded since 1984.

Retreating and thinning of glaciers leads to the formation of new lakes and the enlarging of the existing ones, known as glacial lakes. They play a crucial role as freshwater sources for rivers in the Himalayan region.

ISRO’s observation will help assess the environmental impacts and develop strategies for risk management from GLOFs and climate change adaptation in glacial environments.

Experts attribute the expansion of glacial lake waters to the rapid melting of glaciers caused by global warming. It heightens the risk of GLOF incidents.

Apart from the Sikkim GLOF, other such major incidents in India include the Kedarnath disaster in Uttarakhand in June 2013 and the Rishiganga-Dhauliganga deluge in Chamoli in February 2021. Besides loss of human lives, they also damaged hydropower projects, bridges and roads downstream.

“ISRO’s findings underscore the pressing need for proactive measures to address the potential disaster challenges posed by expanding glacial lakes in the Indian Himalayan Region,” said Anoop Nautiyal, founder of environmental action and advocacy group SDC Foundation.

ISRO’s insights

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

In all, 676 glacial lakes out of the total 2,431 lakes larger than 10 hectares observed during 2016-17, had significantly expanded since 1984. As many as 601 of the 676 lakes more than doubled their size, while 10 grew between 1.5 and 2 times and 65 lakes 1.5 times.  Out of the total expanding lakes, 130 are in India, with 65, 7 and 58 lakes located in the Indus, Ganga, and Brahmaputra River basins, respectively. Elevation-based analysis reveals that 314 lakes are located in the 4,000 m to 5,000 m range and 296 lakes are above 5,000 m elevation.

Glacial lakes are categorised based on their formation process into four broad categories, namely moraine-dammed (water dammed by moraine), ice-dammed (water dammed by ice), erosion (water dammed in depressions formed by erosion), and other glacial lakes. Moraines are materials left behind by a moving glacier. They are usually soil and rock. The report shows that out of the 676 expanding lakes, most of them are moraine-dammed (307) followed by erosion (265), other (96) and ice-dammed (8) glacial lakes.

The Chorabari glacial lake outburst in Kedarnath in 2013 and the South Lhonak glacial lake outburst in 2023 were moraine-dammed, while the Rishiganga-Dhauliganga deluge in Chamoli in February 2021 was from an ice-dammed lake. For instance, satellite mapping revealed long-term changes in the Ghepang Ghat glacial lake (Indus River Basin) at an elevation of 4,068 m in Himachal Pradesh, showing a 178% increase in size from 36.49 to 101.30 hectares between 1989 and 2022. The rate of increase is about 1.96 hectares per year (see photo combo).

The long-term changes in the Ghepang Ghat Glacial Lake area from 1989 to 2022
The long-term changes in the Ghepang Ghat Glacial Lake area from 1989 to 2022 ISRO

What experts say

The continuous increase of greenhouse gases has led to a catastrophic rise in the planet’s temperature due to global warming. The Himalayan mountain range, often referred to as the third pole, is highly sensitive to changes in the global climate, posing a threat to India, which carries out large-scale developmental activities in the Himalayan regions.

This global warming led to melting and shrinking of glaciers and thus, expansion of glacier lakes, posing the threat of increasing GLOF frequency in the high-slope downstream that have habitation and infrastructure. However, experts say there is a lack of study on the increasing GLOF frequency.

“There is no study that clearly tells about the trend of frequent GLOFs in India and the Himalayan countries,” Dr Kalachand Sain, Director, Wadia Institute of Himalayan Geology told this newspaper. “However, researchers from the University of Potsdam are of the opinion that the risk of GLOF in the eastern Himalayas is three times higher than in any other Himalayan region. Effective risk assessment, early warning systems and community preparedness are crucial in mitigation of the impact of GLOFs,” he adds.

Another expert says sustainable land use planning and climate change adaptation strategies are imperative to address the root causes of glacial lake expansion. “Collaboration among scientists, policymakers and local stakeholders is essential to develop holistic solutions that safeguard lives, livelihoods, and ecosystems in the face of these grim and evolving environmental challenges,” says Nautiyal.

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