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 rising temperature in the upper reaches of the Himalayas. Worryingly, the study has also found that the rate of retreat is increasing.
According to various studies, the mean glacial retreat rate between 1935 to 1996 was 20 meters per year which has increased to up to 38 meters per year after that. The studies show that retreat has further gained steam with Gangotri retreating by about 300 meters in the past decade or so.
Rakesh Bhambri, a scientist at the Central government run institute and lead author of the yet to be published study said their fresh estimation of the retreat is based on the comparison of the 1935 map of the Geological Survey of India (GSI) with the current situation in the region.
"Our fresh estimation shows that the glacier has retreated by 1700 metres, and its retreat rate is increasing," he said. He added that the retreat rate has been increasing with every passing decade and if the present retreat rate continues, it will take about 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 Uttarakhand Himalayas, with a length of around 30 kms, width of 0.5 to 2.5 km and an area of around 143 sq km. The melt water from this glacier, that emerges at its snout at Gaumukh at a height of 3,950 metres, is the source of the Bhagirathi River, which later meets the Alaknanda River to form Ganga at Devprayag.
Bhambri said glacier retreat and other associated changes in the area is also leading to morphological changes in the region.
In March , Centre informed Rajya Sabha that the Gangotri glacier had lost nearly 0.23 square kilometre area in 15-year period (2001-2016). Bhambri said most of these changes are happening due to changes in the pattern of snowfall and rainfall in the area, apart from other factors, like 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 added that glacial retreat in the Himalayan region is likely to increase in view of climate change, leading to debris flow activities in glaciated regions from the surrounding moraines in the near future. "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, there was a glacial burst in Chamoli district lead to a flash flood in river Dhauliganga ravaging Raini village and two hydro power plants, resulting in death of about 170 people.
Kireet Kumar, scientist at Almora-based G.B. Pant Institute of Himalayan Environment and Development, who has also studied the Gangotri glacier area, said that over the last decade , the average rate of retreat of the Gangotri glacier has been around 12 to 13 metres a 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".
Kalachand Sen, director Wadia Institute of Himalayan Geology said scientists at the institute are studying the Gangotri glacier area as it is the source of Ganga and 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 said.
There are 9,575 glaciers in the Indian Himalayas of which 968 are located in Uttarakhand. Currently, less than two dozen glaciers are being monitored in the state including Gangotri , Chorabari , Dunagiri , Dokriyani and Pindari.