Potential Proglacial Lake Discovered on Drang Drung Glacier

Image of the breathtaking Drang Drung Glacier from 2012 (Source: Poonam Agarwal/Flickr).

In the northwest reaches of the Himalayas, most glaciers, with a few exceptions in the Karakorum, are showing signs of rapid retreat due to climate change. With long-term climate projections indicating the rise of local minimum temperatures by over 4 degrees Celsius above pre-industrial levels by 2100, the formation of glacial lakes is predicted as the glaciers melt, which could, in turn, have serious socio-environmental impacts.

One glacier already under threat, the Drang Drung, located in the Zanskar region of Jammu and Kashmir, is the focus of a recent study published by Irfan Rashid and Ulfat Majeed in Environmental Earth Sciences. It has shrunk over a seventh of its size in the last 46 years from 1971 to 2017. Using the latest earth observation data, Rashid and Majeed discovered the formation of a potential proglacial lake that began in 2008 and has been growing exponentially since 2014. In fact, within the last four years, the rate of retreat at the snout of the glacier appears to have “radically accelerated,” the authors note.

Tucked in a high-altitude, cold, and arid region, the Drang Drung glacier is a massive ice glacier at a whopping length of 23.3 kilometers, almost 15 miles long. Its runoff contributes as a major source of the Zanskar River, a tributary of the mighty Indus River. Additionally, the glaciers of the region play a crucial role in sustaining the area’s economy and energy supply.

But, to date, analysis on the evolution of glacial lakes and their hazardous potential in the northwest Himalayan region is limited. “Formation and behavior of proglacial lakes over the Jammu and Kashmir region have not been studied in much detail, and hence this region remains a data void,” Rashid explained to GlacierHub.

Despite studies in recent years to account for glacial recession and catalog the formation of glacial lakes in the Himalayas as a whole, data on glacial lake evolution, mass balance, snow cover dynamics, and other factors remain scanty. The study sought to provide a more comprehensive assessment of changes in the Drang Drung area. The dangerously high retreat rate in India’s Kashmir compared to other high-altitude glacierized regions in Asia indicates with high probability that this substantial home to glaciers could be lost before the end of the century, according to the article.

With other related implications in mind like streamflows, hydropower capabilities, and tourism, the study highlighted the importance of evaluating the regional changes to the water resources so that “policymakers are equipped with scientifically robust knowledge that will help in framing policies aimed to sustain the ever depleting water resources in the region.”

Toward this aim, Rashid and Majeed used a Glacier Bed Topography (GlabTop) model to estimate Drang Drung’s glacial thickness and glacier bed overdeepenings (characteristics of valleys and basins eroded by glaciers).

“These overdeepenings in the glacier bed provide an idea about the likelihood of formation of proglacial lakes in the future given the retreating behavior of glaciers,” said Rashid. Being able to input meteorological and climate projections, the researchers were able to simulate what portions of the glacier have the potential to hold water and form lakes as the glacier retreats in upcoming years.

Their conclusions were alarming. Since 1971, the glacier has receded a total of over 925 meters, the length of eight Olympic-sized soccer fields stretched out together. Over the past 46 years, the team distinguished three retreat rates: from 1971 to 2000, the glacier retreated at 22.76 meters a year; between 2000 and 2014, the rate slowed to 6.07 meters a year; and since 2014, the pace accelerated rapidly to 60 meters a year, a length just short of two NBA-size basketball courts.

In terms of the new lake, the team’s assessment revealed that the lake’s rapid growth has a potential peak discharge capacity between 2,343 and 2,667 cubic meters of water per second. For a bit of context on this capacity, in 2013, the outburst of the Chorabari lake in Kedarnath (a devastating flood that killed more than 6,000 people and destroyed critical infrastructure including 30 hydropower plants) released a peak discharge of only 783 cubic meters a second. This could mean that the burst of this new moraine-dammed proglacial lake at Drang Drung has the potential to release 3.5 times more discharge than the fatal 2013 outburst, increasing the vulnerability of communities living downstream.

On top of this finding, another portion of the team’s analysis indicated that temperature warming under current projections could lead to the formation of up to 76 new lakes in the region, although this remains entirely dependent of the future retreating behavior of Drang Drung. In addition, with a massive storage capacity following melting, the potential peak discharge rates were estimated to be at a whopping 35,000 to 48,000 cubic meters of water per second.

Despite the increased vulnerability discovered by the researchers, Rashid is unaware of any disaster risk preparedness initiatives to support the vulnerable communities.

“I do not think the communities have been sensitized with the implications of proglacial lakes and their vulnerability to GLOFs [glacial lake outburst floods],” Rashid told GlacierHub. “Since no such disaster has been reported in the regions, the policymakers seem to be in deep slumber. There are at least four such lakes that have constantly been growing in size since the past two decades in the Zanskar region only, and nobody seems to bother about it. I think the perception and response could be altogether different in case, and God forbid, a GLOF strikes the region.”

For the sake of the surrounding communities, the authors hope a major disaster isn’t the first motivator to get policymakers to discuss the necessary warning systems and other measures to protect the local people against the rising risks of climate change.

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