The 1994 flood: A scene below Wangduephodrang Bridge

27 January, 2009 - Of the 14 risky glacial lakes in Lunana, Lake Thorthormi is on the brink of breaching its walls. Geology department say they are working on it.

Lake Thorthormi is the largest glacial lakes in Bhutan, with a size of 3.42 sq. km, and thrice the dimension of Lake Lugge that burst in 1994. Geologists say the massive ice surrounding Lake Thorthormi is melting fast at 30-35 metres a year, and is filling up the lake quick. The natural dam holding the lake can stand only so much volume of water, say geologist.

Lake Thorthormi feeds Punakha Pho Chhu and if it bursts, geologist say, it could inflict enormous damage downstream. Lake Lugge when it ruptured flooded villages on the way including Punakha town killing 21 people and uncountable livestock. Lake Thorthormi is thrice the size of Lake Lugge.

A glacial expert, Dr Yeshi Dorji, of the geology department, said that measures were being planned for this year and beyond to reduce the water level of Lake Thorthormi and establish early warning system for the communities downstream. UNDP and European commission funded the mitigation works at US$ 7.8 million.

“Excavation works on Lake Thorthormi will begin by June this year but before that necessary equipments and rations would be transported to the glacial site,” he said.

But it was going to be an uphill battle. Pumps, to siphon off water from the lake, did not work properly and it was too heavy to transport machineries. It was also risky to utilize them as it could breach the glacial lake walls. All works had to be done manually with the help of tools such as spade, pixel and crowbars among others.

Mitigation works had numerous problems such as sizes of boulders over 2m that could not be broken by sledgehammer or moved. There was also continuous seepages from the lakes which compelled people to work in freezing cold water. Frequent rains accompanied by cold breeze aggravated the problem.

“The work output is reduced drastically as the labourers have to work with knee-deep water,” said Dr Yeshi Dorji. “The yearly ?work was also limited from June till September as during the other months the passes to Lunana got blocked.”

Tools and rations had to be transported to the glacial site took almost 12 days uphill on foot. “Other countries unlike us could safe time using huge choppers but for us is expensive to hire and there is risk due to climate conditions,” said Karma Toeb of the geology department. Choppers suitable for such terrain cost US$ 200,000 for a trip.

Geologoy officials present during the recent workshop on GLOF Risk Mitigation said that mitigation measures were challenging and proper assessment on the barrier characteristics had to be carried out in order to avoid mishaps. “We don’t want to trigger a GLOF by ourselves,” said a project official.

Moreover, engineering designs have to be modified to suit the terrain while the excavation is in progress and the hazard zonation carried out should be implemented so that the development activities are not exposed to disaster, they said.

Meanwhile, scientists say the temperature in the Himalayan region was rising twice as fast as the global average and that the glaciers were in rapid retreat.

“Himalayan glaciers are retreating at rates ranging from 10 to 60 m per year with many small glaciers already disappeared,” said the vice president of Disaster Management Centre of Nepal, Bishal N Upreti,

The Department of Disaster Management under Home Ministry has also carried out few ‘non structural’ measures like spreading awareness on disasters, setting up response mechanisms and establishing relief funds for disaster mitigation.

A community study carried out along the Pochu Basin stated that Samdingkha town under Toewang gewog would be the most effected in case of a glacial flood. The town was badly hit during the 1994 Lake Lugge outburst. It has 15 households of about 300 people.

Geology officials told Kuensel that the mitigation works had to be started before 2010, or else the situation could worsen.