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Low-altitude Himalayan glaciers in India melting at fast rate

New Delhi : Low-altitude Himalayan glaciers are more sensitive to climate change and are losing water at a much faster pace than the ones in higher reaches due to rising temperatures, a new study on the Indian Himalayas has shown.

The low-altitude glaciers lost a significant amount of water in the past three decades, creating a potential water risk in these regions, the study conducted by researchers from the Bengaluru-based Indian Institute of Science (IISc) has stated.

A study of 146 glaciers spread over 660sq km in Chandra basin in the western Himalayas has estimated the loss of volume, bringing some understanding on the behaviour of glaciers in the wake of climate change.

The Chandra basin is located in Lahaul–Spiti district of Himachal Pradesh and has over 700 square km of glaciated area. It has over 200 glaciers at different altitudes and its basin consists of valley and mountain-type glaciers. Glaciers in the basin predominantly receive accumulation in the form of snow in the winter -October to April - period.

The melt water from Chandra basin gets joined with water from the Bhaga basin to form Chandrabhaga, which becomes the Chenab that flows into Jammu & Kashmir and plains of Punjab.

The study by IISc's Sayli Atul Tawde, Anil V Kulkarni and Govindasamy Bala investigated the mass balance of 146 glaciers in the Chandra basin between 1984 and 2012, and found a water loss of 18 per cent of the total basin volume and 67 per cent for small and low-altitude glaciers, indicating a looming water scarcity crisis for villages in this valley.

An improved understanding of fresh water stored in the Himalaya is crucial for water resource management in South Asia and can be inferred from glacier mass-balance estimates. However, field investigations in the rugged Himalaya are limited to a few individual glaciers and short duration.

Therefore, recently an approach has been developed that combines satellite-derived snowlines, a temperature-index melt model and the accumulation-area ratio method to estimate annual mass balance of glaciers at basin scale and for a long period, said the authors of the study that was published in the international general Annals of Glaciology.

The total ice volume estimated for these glaciers was 62 gigatonnes (with a margin of ± 16 gigatonnes). In total, the Chandra basin has experienced a water loss of 11.1 gigatonnes (with margin of ± 8 gigatonnes) from 1984 to 2012, which is about one-fifth of the total estimated volume.

“This is the first time, not only in India but globally, that we have an estimate of how much volume and mass of glaciers has been lost over a period of time in a large basin. This is the first reliable estimate of both how much water is stored and how much has been lost in the past 30 years,” Kulkarni, professor at the Divecha Centre for Climate Change at IISc-Bengaluru, who led the research team, was quoted as saying.

“I will like to caution that there is no danger of the glaciers vanishing in new future,” Kulkarni said, adding the “small ones” may not be there in the long run. The study would help in better understanding of fresh water stored in the Himalayan glaciers and could be crucial for water resource management to implement necessary mitigation measures, he added.

The study also measured sensitivity of Chandra basin glaciers to temperature rise. Sensitivity analysis suggests that a 20 per cent increase in snowfall can offset changes in mass balance for a 1-degree temperature rise, it said.

The loss of volume in low-altitude glaciers seen was substantial, said Kulkarnai, adding that it suggested that small villages located in this valley might experience water scarcity because mountain communities depend on water supplies from low-altitude glaciers.

The glaciers in the Himalayas constitute the third largest ice mass in the world after the Arctic and Antarctic regions. Rivers originating from these glaciers, including Ganga, Brahmaputra and Indus, are the primary source of water to the population downstream.

The amount and timing of melt from these glaciers are strongly related to local precipitation and temperature and recent studies have suggested that glacier melting could accelerate in the future due to climate change.

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