Gangotri glacier retreated by about 300 meters last decade; Here's why?

New Delhi: In the Gangotri Glacier, the average retreat rate from 1935 to 1996 was 20 metres per year, but it has since increased to up to 38 metres per year. The retreat has accelerated, with Gangotri retreating by about 300 metres in the last decade or so, as per different studies on the Gangotri glacier. This glacier is in the Uttarakhand Himalayas, where the Ganga river originates. It receded by 1,700 metres between 1935 and 2022, according to a study conducted by the Wadia Institute of Himalayan Geology in Dehradun, owing to decreased snowfall and increased rain, as well as rising temperatures in the Himalayas' upper reaches. Worryingly, the study discovered that the rate of retreat is accelerating. The Gangotri glacier in the Uttarakhand Himalayas, from where the Ganga river originates, retreated by 1,700 metres between 1935 and 2022, a study by Wadia Institute of Himalayan Geology, Dehradun has found, attributing it to reduced snowfall and more rain, apart from the rising temperature in the upper reaches of the Himalayas. Worryingly, the study has also found that the rate of retreat is increasing.

Rakesh Bhambri, a scientist at the Central government-run institute and lead author of the yet-to-be-published study, stated that their new estimate of the retreat is based on a comparison of the Geological Survey of India's (GSI) 1935 map with the current situation in the region. "Our most recent estimate shows that the glacier has retreated by 1700 metres, and the rate of retreat is increasing," he said. He added that the rate of retreat has been increasing with each decade and that if the current rate of retreat continues, it will take approximately 1,500 years for the entire Gangotri glacier to melt. “But this can’t be accurate as we don’t know how contributing factors like temperature and rainfall and snowfall will change in the coming years. The decline in the glacial mass, which we are studying currently, will give us a more accurate estimation in the coming time.” 

Gangotri is the largest glacier in the Uttarakhand Himalayas, with a length of about 30 kilometres, a width of about 0.5 to 2.5 kilometres, and an area of about 143 square kilometres. The melt water from this glacier, which emerges at its snout at Gaumukh at a height of 3,950 metres, forms the Bhagirathi River, which later joins the Alaknanda River to form the Ganga at Devprayag. As per the report published in HT. 

According to Bhambri, glacier retreat and other associated changes in the area are also causing morphological changes in the region. The Centre informed Rajya Sabha in March that the Gangotri glacier had lost nearly 0.23 square kilometres in 15 years (2001-2016). According to Bhambri, the majority of these changes are the result of changes in the area's snowfall and rainfall patterns, as well as other factors such as global warming. “The overall pattern is that rainfall has increased in the area and snowfall has decreased. Where earlier major snowfall would protect the glacier, the increasing rainfall is now leading to faster melting of the glacier. Local people also attest to the fact that earlier there used to be heavy snowfall, which is no more the case,” Bhambri said,

He also stated that glacial retreat in the Himalayan region is expected to accelerate due to climate change, which will result in debris flow activities in glaciated regions from surrounding moraines shortly. “Against this backdrop, our efforts are to focus on studying stability, structure and strength of moraines near the glacier to mitigate the risk of glacial debris flow and glacial lake outbursts in the region.”

In 2021, a glacial burst in Chamoli district caused a flash flood in the Dhauliganga, destroying Raini village and two hydropower plants and killing approximately 170 people. Kireet Kumar, a scientist at Almora's G.B. Pant Institute of Himalayan Environment and Development who has also studied the Gangotri glacier area, stated that the average rate of retreat of the Gangotri glacier over the last decade has been around 12 to 13 metres per year.

“The average temperature change in higher reaches of the Himalayas is more compared to the global average. This coupled with changes in rainfall and snowfall pattern is contributing to the glacial retreat and decline in the overall mass of the Gangotri glacier,” Wadia Institute of Himalayan Geology director Kalachand Sen stated that scientists at the institute are studying the Gangotri glacier area because it is the source of the Ganga and a large number of people visit the area.

“In the 2013 Kedarnath tragedy, a moraine-dammed glacial lake outburst created havoc downstream of Mandakini and its tributary river valleys in the region. The Gangotri area is frequently visited by pilgrims and mountaineers especially Tapovan, Sundervan and Kalindi Pass. Given the risk factors involved, investigation of such events is important for future planning and mitigation of hazards such as glacial lake outbursts in the region, in the interest of the public and the sacred region as a whole,” Sen quotes. The Indian Himalayas have 9,575 glaciers, 968 of which are in Uttarakhand. Currently, less than a dozen glaciers in the state are being monitored, including Gangotri, Chorabari, Dunagiri, Dokriyani, and Pindari.