In Bhutan, recent freak weather phenomenon and varying degrees of change in the climatic-pattern has become a cause for anxiety
By Rinchen Dorji
Rising temperatures as a result of climate change are melting Bhutan’s immense collection of glaciers in its mountainous north, threatening significant human and economic devastation.
Freak weather patterns, like the recent late spate of monsoons, has affected thousands of farmers across the country as untimely rainfall inundated most freshly-cut paddy which is unexpected at this time of the year.
In a latest development officials from the National Center for Hydrology and Meteorology (NCHM) said the 700 glaciers in Bhutan are losing its mass or retreating at an alarming rate. Experts have warned that the glaciers could disappear in the next 50 years if the trend continues.
Officials reported that between 2004 and 2019, Ganju La glacier, located at the Pho Chhu basin has retreated at an average retreat rate of 11.4 metres (m) per year with a total shrinkage of 0.081 km2.
A glaciologist with the National Centre for Hydrology and Meteorology (NHCM), said the new findings are based on two benchmarked glaciers – Ganju La and Thana.
He said the Ganju La glacier which has a total surface area of 0.2013 km2 in 2004 has lost 27.6 percent of the initial surface area. In 2019, the maximum thickness of the glacier was recorded at 96.44m.
Glaciologist Toeb Karma said the total retreat at the glacier’s terminus (glacier’s toe or snout) from 2004 until this year was 182 m.
He said comparing the glacier mass added and mass loss, the total cumulative loss from 2004 to 2019 is negative 28.5 metre water equivalent per m2, which means the glacier lost is more than the glacier formed, and which translates to about 5,000 tonnes of water lost.
While the effects of climate change may still feel theoretical in some countries, they have become all too real in Bhutan, where glaciers are now melting at a rate of almost 30 to 60 meters a decade. The majority of people practice subsistence farming on tiny plots of land that are extremely vulnerable to flooding.
Many studies conducted over the years has revealed that glaciers in the Himalaya are melting faster than in other parts of the world. Runoff begins to accumulate in unstable lakes on the glaciers, and when these lakes become too heavy, their natural barriers burst. The result is a mountain tsunami that destroys everything in its path downstream.
A study conducted by UNDP in the early 2000s found out that the glacier retreat rate in Himalaya of Bhutan was more rapid than the retreat rate in Nepal. “Glaciers are retreating at a rate of 7.36 metres in a year,” he said.
“There is an average of 10.7 percent shrinkage in glacier area and 3.28 percent increase in the lake area,” the report said.
The situation is no better with Thana glacier which is located in the Chamkharchhu basin. The maximum thickness of Thana glacier in 2018 was 228.86m but the loss has been rapid over the years with an average retreat rate of 18.2 m annually.
Records with NCHM show that the glacier has lost a total area of 1.49km2 from 1980 until last year.
“Thana has lost 28.64 percent of its surface area. In the latest record, the total surface area of the glacier was 3 km2. Within three years, the loss is more than the glacier formed with a total cumulative of negative 5.98 metre water equivalent per m2. The terminus has also retreated by 726 m from 1980 to 2020,” a report from NCHM stated.
NCHM officials said that similar melting is happening across all other glaciers in the county. Toeb Karma said if the climate gets worse than the current scenario, the glaciers may all disappear in the next 50 years if measures are not taken today.
According to geology officials, the Thorthormi ( Thorthormi) lake, 4,500 metres above the sea level, has become critical and poses potential dangers. The debris covered glacial lake is expanding because the glaciers are melting.
The Thorthorm (Thorthormi) lake is located between the Luggye lake that flooded in 1994 and the Raphstreng lake. “The moraine dam between Thorthormi and Raphstreng is not thick,” the glaciologist said. “There is ice core in the moraine and the moraine will become weak with the ice melting.”
The Thorthormi lakes left lateral moraine was eroded during the 1994 flood. “The Raphstreng lake where artificial canalising had been carried out would not be able to hold the water from the Thorthormi (Thorthormi) lake incase the lake leaks because of the melting moraine,” said Karma Toeb.
According to a geomorphologist, in a worst-case scenario, there could be a chain reaction if one of the lakes burst in Lunana. The volume of water in the reservoir is about 18 million cubic metres, therefore it is only wise to secure the downstream now.
At one time, one of Thorthormi subsidiary lakes breached causing a minor glacial lake outburst flood. The breaching of the subsidiary lake II helped drain out about 2.73 million cubic metres of water from the main lake avoiding a disaster.
A team of experts from NHCM who visited Throthormi lake to assess the “scenario” reported that the breach was caused by melting of ice in the Thorthormi lake which caused a glacial surge.
About 25 out of 2674 glacier lakes in the country are identified as potentially dangerous of bursting and flooding the valleys and plains down streams. The action taken so far by the Bhutanese government is to be seen as prudent preventive and adaptive short-term response to the perceived threats of GLOF.
The country remains almost helpless when it comes to mitigating the risks of permanent retreat of glaciers that feed major rivers in the region.