Thorthormi Tsho is a glacial lake perched precariously at 4428 meters above sea level in the remote Lunana area of northern Bhutan. Rated as one of Bhutan´s likeliest future catastrophes, a breach and outburst flood through Tsho´s unstable moraine walls would most likely spill into the also vulnerable Raphsthreng Tsho 80 meters below, with the combined flood suddenly releasing up to 53 million cubic meters of water and debris into the upper catchment of the Po Chu river.
WWF said that the prospect of such an outbreak is “frightening”. The release added that for Bhutan, outflow from Thorthormi Tsho include crop destruction and livestock losses over more than half of the fertile and economically critical Punakha and Wangdi valleys, loss of a vital bridge and roads, and damage to hydropower facilities under construction. Punakha Dzong, a 14th century royal palace and religious centre, would be among 16 historic monuments at risk
It further said that the new lake has nearly tripled in size since 2001 while the moraine dam holding it has halved its height at the apex over roughly the same period.
Bhutan government, which is monitoring the growth of the glacier under Japanese assistance, has sought assistance to reduce the dangers posed by Lake Thorthormi by artificially draining its waters.
A large effort by the government, communities and WWF, supported by the Global Environment Facility, the United Nations Development Program and the Austrian Coordination Bureau this year succeeded in lowering the lake level by 86 cm, in the first phase of a project intended to artificially lower the water level at Thorthormi Lake by 5 metres in 3 years, the release added.
The release quoted Tariq Aziz, Leader of WWF´s Living Himalayas Initiative, as saying, "The story of Thorthormi lake is shaping up to be a story of successful adaptation to climate change," adding, "However, it is also a story of the risks that climate change is building for communities and the costs and complexities of successful adaptation work."
A team of over 300 workers from 20 districts of Bhutan and from all walks of life walked for up to 10 days to reach the site and dig and realign existing outlet channels to safely drain water from the lake. “The team braved thin and frigid air and harsh weather conditions, including the assault of Cyclone ´Aila´ in May 2009,” the release said.
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