Remote sensing mapping shows that the Himalayas include around 7,500 glacier lakes in Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh. Of these, 190 have been classified as having a “very high” risk of generating a Glacial Lake Outburst Flood (GLOF), which occurs when water contained by ice walls or moraine is released abruptly. Himachal Pradesh is particularly exposed to this menace. According to a remote sensing-based study conducted by the Himachal Pradesh Council for Science Technology-Environment (HIMCOSTE), flash flood risk rises in Himachal and Uttarakhand and the number of glacier lakes capable of causing flash flooding in the state has nearly doubled from 562 in 2019 to 1,048 in 2023. These frozen lakes are situated in the Satluj watershed, which extends from Mansarover Lake in Tibet, the river’s source, to Jhakri in the Shimla district.

The National Disaster Management Authority (NDMA) classifies 48 glacial lakes in Himachal Pradesh as “high-risk.” Sikkim has 40, Ladakh has 35, Arunachal Pradesh has 28, Jammu and Kashmir has 26, and Uttarakhand has 13. Landslides and earthquakes are among the elements that cause glacial lake outbursts.

Of the 1,048 lakes identified in 2023 in the Satluj catchment area, 900 are small, covering less than five hectares apiece, 89 cover five to ten hectares, and 59 cover more than ten hectares.

Over time, the number of glacial lakes has gradually increased. It suggests that the consequences of climate change are more severe in the higher Himalayan region. “The rapid melting of glaciers and less snowfall during the winter could be the reasons for the rise in lakes,” said Dr Ashim Sattar, a glaciology expert and assistant professor at IIT Bhubaneswar.

He stated that basin-wise investigation revealed that the Upper Satluj basin is more prone to glacial lake formation. “The average temperature in the high altitude areas is rising faster than the lower areas,” Sattar told reporters.

Flash flood risk rises in Himachal and Uttarakhand, two dozen villages and towns along the Sutlej River in Himachal Pradesh, and Parchu Lake in Tibet, China, fills up again.

Though the indicators are not as severe as in 2005, when a lake breach caused havoc in towns around Sutlej, authorities have since kept a close eye on the lake’s water level. The discharge from Parchhu Lake is not alarming, but water accumulation in speed and volume can cause flash floods in downstream areas.

The study, which examined multi-spectral satellite photos, warns that the rise in glacier lakes in Himachal Pradesh’s river basins might have severe downstream consequences if the lakes breach their boundaries for whatever reason.

Climate change harms glaciers throughout the Himalayan region, resulting in a drop in cryospheric cover. This has resulted in additional high-altitude glacial lakes, becoming increasingly unstable as water levels rise and glaciers calve. These lakes are at risk of bursting, and depending on the water volume, velocity, and spread, they may jeopardise downstream communities and infrastructure.

The Rs 150 crore initiative, authorised in July, is part of a total of Rs 12,554 crore approved by the Centre for urban flood management, firefighting services, and other disaster mitigation activities in states and union territories.

As part of the initiative, all government and state authorities, including scientific institutions, the Indian Army, and the Indo-Tibetan Border Police (ITBP), have expedited high-risk glacial lakes to examine structural stability and probable breach points.

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