Winter snow deficit poses growing risk of GLOFs in Himalayas

The reduced snowfall in the Himalayas increases glacial lakes, which pose a growing risk of lake outburst floods in the Himalayas, warn glaciologists.

They call for increasing preparedness, international cooperation and climate adaptation.

The Himalayan state of Himachal Pradesh has seen a large deficit in winter precipitation, of 31 per cent, since 1 January. Nine out of its 12 districts have received deficient precipitation, says the Meteorological Centre in Shimla.

Meteorologists told IANS that, as warmer winters continued for the second consecutive year across India, the cumulative countrywide rainfall from 1 January to 29 February has shown a large deficit, of 33 per cent. The actual rainfall recorded during the winter season was 26.8 mm against the normal average of 39.8 mm.

According to meteorologists, increasing global warming has been altering weather patterns, leading to anomalies in temperature and rainfall patterns.

The prime weather system in the region, that of western disturbances, continued to dodge the western Himalayas as they mostly travelled in the upper latitudes.

Western disturbances are known to drive the weather activities and bring winter weather events to north-west India and adjoining areas of central India. Both the intensity as well as frequency of these western disturbances has been on the lower side this winter season.

Western disturbances are primarily disturbances originating in the west and travelling in the upper atmosphere in the subtropical westerly jet. They arrive in the Indian Subcontinent during the winter. Their frequency peaks from December to February, to an average of four to five events per month.

Climate change and associated glacier recession have led to the formation of new glacial lakes and the expansion of existing ones across the Himalayas recently, however. Many pose a potential glacial lake outburst flood threat, a climate change-induced threat to downstream communities and infrastructure.

The term 'glacial lake outburst flood', or GLOF, refers to the catastrophic release of a water reservoir that has formed at the site of a glacier. Glaciologists warn of events akin to last year's Sikkim GLOF event in other Himalayan states too.

According to a recent report on the Himalayas by the University of Zurich, glacial lakes are highly dynamic water reservoirs that respond to climate change by expanding in number, size and volume. This is particularly evident across the mountains of Asia, including in the Hindu Kush Karakoram Himalayas, Tien Shan and Tibet.

As a result of climate change and consequent accelerated glacier recession, the number of glacial lakes in Hindu Kush Karakoram Himalayas increased from 4,549 lakes (398.9 sq km) in 1990 to 4,950 lakes (455.3 sq km) in 2015.

Several large-scale and regional assessment studies confirm the growth of glacial lakes and their hazardous potential across Asia.

Jammu and Kashmir has the highest combined exposure to potential GLOF events, with 556 lakes, including some designated 'very high danger' and 'high danger' lakes.

It is followed by Arunachal Pradesh, with 388 lakes, and Sikkim, with 219 lakes.

Sectorwise, Jammu and Kashmir face the greatest GLOF threat to roads and populations, whereas the threat to croplands and hydroelectric power is greater in Arunachal Pradesh and Sikkim, respectively.

However, the highest-priority lakes, where urgent monitoring and local site investigations are recommended, include thirteen lakes in Sikkim, five in Himachal Pradesh, four in Jammu and Kashmir, two in Uttarakhand and one in Arunachal Pradesh.

As glaciers melt, risks of catastrophic events — landslides, sudden ice shears and, in some cases, GLOFs — will rise.

Experts say the warming observed in recent decades has been accompanied by increased avalanche frequency in the western Indian Himalayas.

Powder snow avalanches tend to occur after intense snow precipitation during cold winter conditions, whereas wet and dense flows often coincide with warm spells, typically towards the end of the winter and early spring. As a consequence, changing climatic conditions may modify avalanche activity. According to the weather models, avalanche probabilities are highest if warmer temperatures persist during these months.

Land cover changes such as afforestation and deforestation are also likely to play a role.

Extensive adaptation therefore needs to begin immediately to prepare for this future, even as mitigation to preserve glaciers as much as possible is also prioritised.