The bursting of a GLACIAL lake, the bursting of a cloud or an avalanche, the impact of climate change or “development” – scientists are not sure what caused the sudden rush of water near Chamoli in Uttarakhand on Sunday morning which briefly sparked fears of a repeat of the 2013 disaster in the state.
By dusk, the prospect of large-scale flooding and destruction had receded. And, as scientists prepared to travel to the site in the high mountains north of Chamoli to determine the cause of the incident, the most talked-about scenario was what glaciologists like to call a GLOF, or a flash flood of a glacial lake. It is a reference to flooding caused downstream due to a breach in a glacial lake.
Receding glaciers, like several in the Himalayas, generally result in the formation of lakes at their tips, called proglacial lakes, often limited only by sediments and rocks. Pushing the boundaries of these lakes can cause large amounts of water to flow into nearby streams and rivers, building momentum along the way by picking up sediment, rocks, and other materials, and causing flooding downstream.
GLOF events are not unusual, but their impact depends on the size of the proglacial lake that erupted and the location. The violation may be due to a number of reasons: in this particular case, for example, an avalanche was reported in the region two days ago.
But while GLOF is considered the most likely trigger for Sunday’s event, there are doubts about this possibility. “We don’t know of any large glacial lake in this region. An avalanche is quite common, and there could have been one, but an avalanche alone would not result in an increase in the flow of water in the river. The water has to come from a source and for now we don’t know what this source is, ”said Professor HC Nainwal, a glaciologist at Hemwati Nandan Bahuguna Garhwal University in Srinagar, Uttarakhand.
“We would have to visit the area to find out what exactly happened. Until then, we can only speculate, ”he said.
Argha Banerjee, a glaciologist working at the Indian Institute of Education and Scientific Research (IISER), Pune, said that it was possible that there was a glacial lake in the area, but that scientists were not aware of it.
“There are hundreds of lakes of this type all over the place. We know many of them, but there may be some that we do not know. After today’s event, I started looking at satellite images and couldn’t find any glacial lakes in that area. But maybe if we look at higher resolution satellite images, we will find one, ”Banerjee said, adding that there are also cases of lakes that form within glaciers, which cannot be detected in satellite images.
“But if there are in fact no glacial lakes in that area, then Sunday’s event would seem to be a bit surprising,” he said.
The surprise is also due to the timing: no possible reason for the sudden rush of water, such as a shower, is expected at this time of year. “Cloudburst would be a rare event this time of year. It looks like a GLOF event right now, ”said Professor AP Dimri from the Faculty of Environmental Sciences at Jawaharlal Nehru University.
But there are other possibilities, as Banerjee suggested.
“It is possible that an avalanche or landslide created an obstruction in the flow of the river or streams in the upper mountains, resulting in a makeshift dam situation. When the pressure of the flowing water became great, the dam probably gave way, causing a sudden gush of water. These are just the possible scenarios. We would know the exact reason only after reaching the site. It could take a day or two, ”Banerjee said.
The Dehradun-based Wadia Institute of Himalayan Geology will send two teams of scientists to the area on Monday to study the possible cause of Sunday’s event, said director Kalachand Sain.
Then there are also issues to consider, such as climate change or disproportionate construction in a fragile ecosystem, which were also supposed to have contributed significantly to the 2013 disaster.
So far, the incident does not appear to have any direct link to construction-related activities, or the presence of large dams, but climate change as a factor is not something that can be ignored, particularly in the formation of proglacial lakes. Most of the Himalayan glaciers are known to be retreating, leading to the formation of several proglacial lakes.
What scientists are almost certain of is that the incident was not the result of any glacier “breaking”. In fact, glaciers are not known to break up like ice sheets do in polar regions. Some chunks of snow near the tip of the glacier can slide downward, but they do not result in the large amounts of water seen in incidents like these.
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