The glacial collapse that caused deadly flooding along the Nepal-Tibet border has renewed attention on the risks facing Bhutan, home to more than 600 glaciers across its northern mountain ranges.
As climate change accelerates the melting of glaciers, water can accumulate in lakes held back by fragile moraine or debris dams. If these natural barriers fail, the resulting glacial lake outburst floods (GLOFs) can send large volumes of water downstream, threatening settlements, infrastructure and livelihoods.
For Bhutan, the danger is not theoretical.
In 1994, a GLOF killed 21 people along the Punatsangchhu River. Since then, the country has strengthened its early-warning systems and invested in measures to reduce the risks posed by unstable glacial lakes.
At a modest emergency warning facility in Wangduephodrang, operators work 24 hours a day to monitor changes in water levels and alert communities when danger is detected.
“The Thorthormi glacier, due to climate change, it has fully transformed into a glacial lake,” said Dechen Peldon, a junior engineer at the GLOF emergency warning facility in Wangduephodrang.
“Now we have to be more vigilant and more concerned.”
The warning centre began operations in 2011 as part of efforts to improve disaster preparedness following the 1994 GLOF.
It oversees a network of sensors installed at glacial lakes and downstream rivers. The sensors detect changes in water levels, while sirens installed in vulnerable communities provide warnings to residents to evacuate when necessary.
Of Bhutan’s more than 600 glacial lakes, 17 are considered potentially dangerous. Some of the most vulnerable lakes are located at the headwaters of rivers that feed into the Punatsangchhu basin.
Four glacial lakes have formed in the area, with two separated by a fragile debris dam. In a worst-case scenario, the collapse of the barrier could release an estimated 53 million cubic metres of water downstream.
Communities closest to the lakes could have only a few minutes to evacuate. For this reason, sirens in the nearest settlements are automatically activated when changes in water levels indicate a possible GLOF.
Further downstream, sirens are activated manually by Dechen and her colleagues when monitoring data suggests a dangerous change. Although the recent disaster in neighbouring Nepal involved a glacier collapse rather than a GLOF, it has reinforced the urgency of their work.
“I’m more alarmed and taking this more seriously,” Dechen said. “We, the control room operators, are more vigilant than we were before.”
The facility works with the disaster management authorities to conduct mock drills and awareness sessions. However, awareness and preparedness remain uneven among communities living downstream.
Pushpa Karki, a 30-year-old café owner near the river, said she was not certain what the warning siren outside her business sounded like.
“I’ve never have been part of any drill,” she says. “They talk about mountain areas being prone to floods, so we are cautious. But I don’t know about the glacier-related flood risk.”
Around 70 percent of Bhutan’s settlements are located along rivers, making communities particularly vulnerable to floods and other water-related disasters.
In addition to strengthening early-warning systems, the government has undertaken measures to reduce the risks at the source.
In 2008, Bhutan began a multi-year project to excavate and widen a channel from Thorthormi glacial lake. The difficult work at high altitude lowered the lake’s water level by around five metres, reducing pressure on the debris dam holding it back.
However, continued glacier melt has caused the lake to fill again. Experts are now exploring methods to siphon water from the lake to reduce the risk of a sudden release.
Bhutan’s leading glaciologist, Karma says that the country’s glaciers were retreating at an alarming rate. “Our glaciers are melting at a very alarming rate,” he highlights.
According to Karma, Bhutan’s largest glaciers are retreating by around 30 to 35 metres a year, while smaller glaciers are receding by approximately 12 to 16 metres.
The changes have also affected his own experience of the mountains. Karma became Bhutan’s first glaciologist after accompanying Japanese experts during glacier surveys. “I could literally climb on the glaciers,” he noted. “But now you cannot do that… it’s so sad actually.”
Karma reiterates Bhutan’s exposure to climate-related risks was particularly concerning because the country contributes relatively little to global emissions while maintaining extensive forest cover.
Bhutan’s laws require forests to cover at least 60 percent of the country’s territory. Despite this, its communities face increasing risks from glacier melt, floods and changing weather patterns.
He says that the fear, the risk, which is being brought to the communities in the country are not Bhutan’s fault.
“I would like to appeal to the rest of the world to take responsibility.”
For the teams monitoring Bhutan’s glaciers, the task is a continuous race against time. Early-warning systems, community preparedness and upstream risk-reduction measures remain central to protecting lives as the country’s glaciers continue to change under a warming climate.
Tashi Namgyal, Thimphu
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