Uttarakhand glacier burst: Experts cite impact of climate crisis
Massive inundation in Uttarakhand’s Rishi Ganga valley caused by a suspected glacial lake outburst flood (GLOF) on a clear winter’s day has unnerved scientists. GLOFs and resulting disasters downstream during extreme rainfall events in glacial regions are commonly forecast by scientists. But this time scientists have seen it happen in winter, when such events are least expected.
The Snow and Avalanche Study Establishment (SASE) of the Defence Research and Development Organisation is stills investigating the matter and has not been able to zero in on the exact reason for the flooding as yet.
“Our team is there. We do not suspect an avalanche. There may be glacial lake formations, but we cannot say with certainty now. We are investigating the entire region,” said Jimmy Kansal, joint director at SASE.
The flood caused large-scale devastation in the upper reaches of the ecologically fragile Himalayas, with 50-100 labourers working on the Rishi Ganga power project missing. Homes along the way were also swept away as the waters rushed down the mountainsides in a raging torrent
It is difficult to say exactly what happened, said D P Dobhal, a former glaciologist at Dehradun-based Wadia Institute of Himalayan Geology.
“Locals have told me that water and debris were flowing at great speed for about 15 to 20 minutes this morning and then the flow reduced gradually. This indicates a lake outburst. It’s possible that water and debris accumulated in a lake in the glacial region of Rishi Ganga valley breached due to an avalanche. Its also possible that the avalanche took place earlier, like yesterday or very early in the morning today. The water filled up in the lake and breached. It may be very similar to what happened in 2013 with the Chorabari lake during the Kedarnath disaster. Only difference is that this time it’s in winter and that was during monsoons,” said Dobhal
In the early hours of June 17, 2013 a flash flood came down upon the overflowing banks of the Chorabari lake in Uttarakhand. Carrying huge amounts of silt and rocks, it killed at least 5,700 people, and left unprecedented damage and destruction.
Dobhal added that GLOFs will increase because of climate change. “Lakes have always formed in glaciers and some glaciers have retreated while some advanced. These are stages. But due to global warming, more glaciers are melting or retreating and there is less snow. This is very apparent in Nepal and Sikkim and not so much in Uttarakhand,” Dobhal added.
Prof Anil Kulkarni of Indian Institute of Science (IISc), Bangalore, also suspected that the flooding may be linked to a GLOF.
“When glaciers retreat, glacial lakes are formed. These lakes are formed in the area vacated by the glacier. Several lakes have formed in the Rishi Ganga valley. We don’t know which one may have burst. In winter, the top layer of these lakes is frozen. During an ice avalanche or a landslide this top layer is breached and water can flow downstream, toppling the earthen dam. This is a common problem seen in glaciated terrain. We have seen this in Nepal but not in Uttarakhand so far. This is a classic case of climate change impact on the glacier. We have again and again highlighted that such disasters will become exceedingly common due to climate change as more and more glaciers retreat,” explained Kulkarni, a glaciologist and scientist at the Divecha Centre for Climate Change, IISc.
Kulkarni’s team has studied various aspects of such glacial lake discharge events. For example, last year the team modelled the impact of a GLOF on a hydroelectric project downstream of Satopanth glacial lake and found that a GLOF, combined with an extreme flood event, can cause extensive damage to the project. The study recommended regular monitoring of the Satopanth lake, especially during post-monsoon season, due to the potential risk it poses to the downstream region when combined with high-intensity rain events.
A large number of hydroelectric power plants (HEP) were damaged in the 2013 cloudburst and GLOF inKedarnath. The 400 MW Jaypee (JP) Vishnuprayag hydro-electric project (HEP), located 28 km downstream of the Satopanth lake, was one of the projects damaged by the 2013 cloudburst.
“Due to the fact that a number of glacial lakes exist within the limits of the Vishnuprayag HEP catchment, GLOF risk assessment for this hydropower station becomes very vital,” a study by Kulkarni’s team said.
Kulkarni’s team, in its science brief on GLOF, recommended long-term strategies to prevent GLOF disasters including identifying locations vulnerable to such events using computer simulations, monitoring lake expansion, determining structural strength of the moraine dam, maintaining safe water level in the lake through siphoning, and determining future glacier lake sites using remote sensing techniques.
On Sunday, there was an avalanche in Rishi Ganga valley 50 to 100 metres upstream of its confluence with Dhauliganga West. A small hydroelectric project of about 11 MW in the Rishi Ganga valley was totally destroyed. The barrage of the Tapovan Vishnugad hydroelectric project has also been damaged and water entered the intake tunnels. Around 50 workers were working at the plant at that time out of them 30 to 35 are feared to have been washed away.
Around 10 villagers who were out with cattle on the mountain slopes may have also been washed away, according to initial reports received by Ravi Chopra, director of the People’s Science Institute and chairman of the Supreme Ccourt-constituted high powered committee monitoring the Char Dham road project in Uttarakhand.
“We cannot comment on this specific event because the ministry of earth sciences doesn’t monitor avalanches. We know that the 2013 Uttarakhand disaster was related to a glacial lake. However, from the climate change perspective we can definitely say that the glaciers to the western side of the Himalayas are retreating while many of those in the eastern side have also recorded advancement of glaciers. So glacial lake disasters are expected,” said M Rajeevan, secretary, ministry of earth sciences.