where he had positioned himself he literally flew to safety.

“All I could see was a river of logs, boxes, haystacks,” he recalled. “In minutes the river ravaged everything on its way. It changed course, destroyed parts of the dzong, and flooded the school soccer field and ripe paddy fields with fish,” he said.

The October flood had claimed more than a dozen lives, damaged acres of farmland, and government and private property worth millions of ngultrums.

The flood was caused by a glacial lake that had burst high up in Lunana nine days walk from Gasa dzong.

Since then several attempts have been made to reduce the risks of another glacial lake outburst flood (GLOF), but geologists say the dangers are far from over with changes in climate.

Since the last inventory of glaciers and glacial lakes in Bhutan by the International Centre for Integrated Mountain Development (ICIMOD) in 2001, 106 new glaciers and 120 glacial lakes have formed in the mountains.

In the past 15 years, 16 new glaciers and 82 glacial lakes had formed in the headwaters of the Phochu alone.

About 140 glaciers and four new glacial lakes had also formed in the headwaters of the Mochu, according to Glaciologist, Karma Toeb, who presented the impact of climate change on glaciers and glacial lakes in Bhutan Himalayas on Thursday.

“If the present trend of climate change continues, there is a possibility of another GLOF,” the glaciologist said. “It is difficult to say when, but the glaciers are melting at an alarming rate.” According to geology experts, the number of lakes posing dangers had increased from 24 to 25. Karma Toeb, who has visited Lunana eight times said that they have identified nine potentially dangerous lakes in the Phochu sub basin, seven in Mangde chu, five in Mochu, three in Chamkhar, and one in Kuri chu.

The more impending dangers could come from fast retreating glaciers.

Karma Toeb said 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,” he said.

According to geology officials, the Thorthomi 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,” Karma Toeb said.

The Thorthomi lake is located between the Luggye lake that flooded in 1994 and the Raphstreng lake. “The moraine dam between Thorthomi 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 Thorthomi 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 Thorthomi lake incase the lake leaks because of the melting moraine,” said Karma Toeb.

According to geomorphologist Deo Raj Gurung, 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,” he said.

A hazard zonnation for GLOF along the Puna tsangchu from Khuruthang in Punakha to Kalikhola is among various mitigation and risk management measures, the department of geology and mines (DGM) with the Netherlands Climate Assistance Programme (NCAP) had prepared.

The project, which would begin soon, is one of the adaptation methods to climate change according to the director DGM, Dorji Wangda.

“A base map on the hazards related to GLOF along the Puna tsangchu can be used as a tool by policy makers and planners in taking decisions, designing and planning developmental activities along the river,” he said.

Presenting the project to stakeholders on Thursday, Deo Raj Gurung said that many important installations and monuments lie along the Puna tsangchu like the Punakha dzong, new Wangduephodrang township, Basochu project, Puna tsangchu project besides thousands of settlements.

The hazard zonnation map along the Puna tsangchu would delineate areas along the river into different zones of different degrees of hazards from GLOF in future.

Meanwhile, the Global Environment Fund had agreed to fund US$ 3.5 million for hazard zonnation map in Chamkhar chu in Bumthang, establishment of an early warning system along the Punakha-Wangdue valley, and artificial lowering of the Thorthomi lake.

By Ugyen Penjore

ugyenpen@kuensel.com.bt