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Uttarakhand's Glacial lake burst - an analysis
Read more on - Polity | Economy | Schemes | S&T | Environment
- A terrible tragedy: On Sunday, 07th Feb 2021, a glacial lake in Uttarakhand burst, triggering a sudden surge of water near Chamoli, reminding people of the 2013 disaster in the state. The flood caused heavy damaged to the hydropower plant nearby. The Tapovan- Vishnugad hydropower plant was damaged amidst a flood of water gushing down the Ganga river. The IAF reported that Tapovan Hydro-Electric Power Dam (Rishi Ganga Project) was completely washed off. After a few hours, the prospect of largescale flooding and destruction had receded. Scientists prepared to travel to the site in the high mountains north of Chamoli to ascertain the cause of the incident. GLOF events are not unusual, but their impact depends on the size of the proglacial lake that burst, and location.
- Most likely: The scenario most talked about was what glaciologists call a GLOF, or "glacial lake outburst flood". It is a reference to flooding caused downstream due to a breach in a glacial lake. The breach can be caused by several reasons — in this particular case, for instance, an avalanche was reported in the region two days ago.
- Glacial lake outburst floods (GLOFs) occur from an unstable natural dam formed from a glacial retreat.
- Glaciers are large bodies of ice moving slowly. So, when a glacier retreats, it leaves behind a large impression in the ground, filling it with water and a lake is formed. This is known as a moraine, which can be impounded by precarious pile of debris and buried ice.
- The moraine dammed lakes weaken as the water level rises and the glacier retreats. They might crumble under pressure from the swelling lake, leading to massive floods.
- Proglacial lakes: So retreating glaciers, like several in the Himalayas, usually result in the formation of lakes at their tips, called proglacial lakes, often bound only by sediments and boulders. If the boundaries of these lakes are breached, it can lead to large amounts of water rushing down to nearby streams and rivers, gathering momentum on the way by picking up sediments, rocks and other material, and resulting in flooding downstream.
- Lakes inside glaciers: While GLOF was being considered to be the most likely trigger for the event, questions exist. As per experts: “We don’t know of any big glacial lakes in this region. An avalanche is quite common, and there could have been one, but an avalanche on its own would not result in an increase in the flow of water in the river. The water has to come from a source, and as of now, we do not know what this source is.” So it is possible that a glacier lake was present in the area but not known to scientists. There are hundreds of such lakes all over the place and it is possible that there is one that experts do not know about. Lakes form inside the glaciers too, which cannot be detected in satellite images.
- Strange timing: The surprise is also because of timing — a possible reason for the sudden rush of water, like a cloudburst, is not expected at this time of the year. Cloudburst would be a rare event during this time of the year. It is possible that an avalanche or a landslide created an obstruction in the flow of the river or streams in the upper mountains, resulting in a makeshift dam-like situation. When the pressure of the flowing water became large, the dam probably gave away, leading to a sudden gush of water.
- Other factors: There are also issues also to consider, like climate change or disproportionate construction in a fragile ecosystem, which were supposed to have contributed significantly to the 2013 disaster as well. Intitally at least, the incident did not seem to have any direct linkage with construction-related activities, or the presence of big dams, but climate change as a factor is not something to ignore, particularly in the formation of proglacial lakes. A majority of the glaciers in the Himalayas are known to be receding, all leading to the formation of several proglacial lakes.
- What it is not: Scientists are certain that the incident was not a result of any glacier ‘breaking off’. In fact, glaciers are not known to break in a manner that ice-sheets in the polar regions do. Some chunks of snow from near the tip of the glacier can indeed slide down, but they do not result in huge amounts of water like those seen in incidents like these.
- Prior warning: The glacier burst has proven right the 2017 prediction of conservationist Rajendra Singh, also known as the ‘Waterman of India’ who after the Kedarnath floods in 2013 had claimed that a similar tragedy was waiting to happen. Singh said "We had informed the authorities concerned that no dams should be constructed on rivers Alaknanda, Bhagirathi, and Mandakani as there are very steep slopes in the area and it is an extremely eco-sensitive zone. The rampant construction continue due to which the recent disaster was inevitable."
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