Hundreds of glacial lakes expanding in Himalayan region, flags ISRO

A little over one in every four glacial lakes larger than 10 hectares in area (100000 sq m) in the Himalayas have increased in size since 1984, increasing the risk of a glacial lake outburst flood or GLOF, a phenomenon that’s become common on account of the climate crisis.

Long term satellite imagery covering the Himalayas has revealed that of the 2,431 glacial lakes larger than 10 hectares in area identified in 2016-17, 676 glacial lakes have expanded notably since 1984. And 130 of the 676 are within India , with 65, seven, and 58 lakes located in the Indus, Ganga, and Brahmaputra River basins respectively, the Indian Space Research Organisation said on Monday.

Around 601 lakes (89%) of 676 have at least doubled in size; 10 have grown between 1.5 to 2 times; and 65 lakes at 1.5 times since 1984. Elevation-based analysis revealed that 314 lakes are located in the 4,000 to 5,000 m range and 296 lakes are above 5,000 m elevation.

Long-term changes in the Gepang Gath glacial lake (Indus River Basin) at an elevation of 4,068 m in Himachal Pradesh, shows 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, Isro has flagged.

This is a major risk that should be managed effectively, scientists said. “Scientists including our team have already highlighted that Gepang Gaht lake has expanded at a major scale and can potentially affect the Manali Leh highway and population downstream. We have already recommended that state governments take precautionary action,” said Anil V. Kulkarni, glaciologist and distinguished Visiting Scientist, Divecha Center for Climate Change, Centre for Atmospheric & Oceanic Sciences at Indian Institute of Science.

He added that the government should also focus on lakes beyond India’s borders. “We need to negotiate and discuss these lakes with neighbouring countries,.

Kulkarni referred to the Lhonak lage GLOF in Sikkim as a case in point.

Last year IISc presented an assessment of current and future GLOF hazard for Gepang Gath Lake, factoring in the prospect of rock and/or ice avalanches cascading into the lake.

Expanding glacial lakes 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.

On October 4-5, 2023 HT reported heavy monsoon rainfall and a glacial lake outburst flood (GLOF) that caused severe flooding downstream in Sikkim that washed away part of the Teesta 3 dam, damaged parts of Teesta 5, wrecked bridges and drowned roads.It was not immediately clear as to what may have triggered the GLOF on Lhonak lake in northwest Sikkim, although the risk had loomed large for at least a decade.

On October 13 last year, HT reported that the risk of another glacier lake outburst flood (GLOF) downstream of South Lhonak lake in Sikkim was real. According to glaciologists at the Divecha Centre for Climate Change, Indian Institute of Science (IISc), a large chunk of ice may have fallen from the glacier into the lake creating waves that toppled the moraine dam leading to a GLOF and causing severe flash floods downstream on October 4 that killed around 91 with many still missing.

“The Himalayan Mountains, often referred to as the Third Pole because of their 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 since the onset of the Industrial Revolution in the eighteenth century. This retreat leads to the formation of new lakes and the enlargement of existing ones in the Himalayan region,” Isro said on Monday.

“As the climate warms, glaciers shrink in size and a lake may be formed, often at the side of the glacier (glacier-dammed lake) or at the front of the glacier, between the glacier and a moraine ridge (moraine-dammed glacier) or another type. As the climate continues to warm, these lakes may grow in size. There is a lot of evidence that there are more lakes than previously. This implies strongly there will be more GLOFs and GLOFs will be bigger (and more damaging),” Miriam Jackson, glaciologist and programme coordinator, cryosphere at Kathmandu-based International Centre for Integrated Mountain Development said last October.