GLOF: preparing for uncertainties

March 23 | Kuensel
By Jigme Wangchuk

The thin moraine wall yields to the pressure of the lake’s rising water level. A deluge twice the destructive power of the 1994 glacial lake outburst flood (GLOF) on the Phochhu comes thundering down, engulfing everything on its the way. The dzong is standing still but may not hold for long; damage on lives and property downstream is appalling and sad. It is a sobering sight to behold. With communication and transportation lines badly severed, people are dying in hundreds where timely medical interventions could have helped. The scrambling nation is yet to comprehend the scale of destruction it has just witnessed. Imagine.

Who can tell the future indeed? Often, though, a little imagination is all that is required. Mankind has never been entirely defenseless against the power and possibilities of the unseen.

Today, in the age of increasing weather inclemencies and ever shifting landscapes, GLOF is perhaps the biggest threat facing Bhutan. There have been devastating floods in the past, of course, but Bhutan is today vulnerable to the impacts of climate change more than ever. Global temperature rise is melting the ice in the high Himalayas at an alarming rate, according to some well-placed climate reports. That means rising water level in the lakes will be too much for the moraine lines to hold. The resulting flood can so be devastating, especially in the lower valleys.

The question is how much do we understand about our lakes and how prepared are we to deal with the chaos that might visit us?

Although Bhutan was aware about the formation of glacial lakes in Bhutan as early as 1940s, it was only after the 1994 GLOF that caused chaos downstream taking life of 20 people and damaged millions worth of infrastructures and properties that the country seriously began employing various measures to monitor, mitigate and create risk awareness related to GLOF hazard, leading to identification of potentially dangerous glacial lakes.

The first ever inventory on glaciers, glacial lakes and potentially dangerous glacial lakes in Bhutan identified 25 lakes as potentially dangerous, five in Mochhu sub-basin, eight in Phochhu sub-basin, seven in Mangdechhu basin, three in Chamkharchhu sub-basin, and one in Kurichhu sub-basin.

According to National Centre for Hydrology and Meteorology’s (NCHM) reassessment report on the glacial lakes in Bhutan, there are 17 potentially dangerous lakes sitting on the country’s major headwaters. A small decrease in the number of “potentially dangerous lakes” provides little comfort, however, because some of them are notoriously inaccessibly for study.

Glaciers and glacial lakes in Bhutan were not studied until 1960. Augusto Gansser, a Swiss geologist while doing survey to compile data on the geology of Bhutanese Himalaya, undertook an expedition to Lunana area where he identified numerous dangerous lakes that had the potential to cause massive floods. Tarina Tsho, which he saw as a threat, was source of flood that destroyed parts of Punakha Dzong in 1983.

Because GLOF are a natural event, to predict them is impossible. The biggest flood that followed in the living memory was in 1994 when Lugge Tsho breached its dam. Today, Thorthormi Tsho and Raphstreng Tsho, which are separated by only a thin moraine line are the major lakes that have the potential to cause GLOF. People of Thanza, a village at the foot of looming lakes, live in constant fear of floods. The small village of about 35 households was deep in slumber when Lugge Tsho broke through with violent force on October 7, 1994.

There were no GLOF early warning systems in the village then. When the village awoke, the flood had left Lunana, taking along with it a woman and her two sons, and a good chunk of village pasture. If there is a GLOF today, people of Thanza will have little time to escape. GLOF experts says that if the fast-narrowing moraine ridge between Thorthormi and Rapstreng breaks, there will be a flood that is at least five times bigger than the one from Lugge Tsho 25 years ago. The alacrity with which the change is coming is alarming. Until recently, the residents of Thanza used to go collect incense with yellow flower called Sangzey Karchu that belongs to family of Asteraceae. Today, the plain is completely submerged under the fast-forming Bey Tsho.

Are we doing enough to prepare for yet another devastating flood that these potentially dangerous lakes could unleash?

“Nothing that we do will be enough because we are dealing with the nature,” says Karma, specialist with NCHM’s Cyrosphere Services Division. “There are a lot of things we need to do and we will continue doing.”

So, what do we have?

Data. Data and reports on glacial lakes and the potential danger they present. NCHM yesterday released three scientific reports – analysis of historical climate and climate change projection for Bhutan, reassessment of potentially dangerous glacial lakes in Bhutan, and Bhutan glacier inventory 2018 – which are expected to help guide policy and decision makers develop and plan strategic interventions.

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