THIMPU -- The Kingdom of Bhutan, tucked between India and China in the foothills of the Himalaya mountain range, is paying the price for global industrialization. To the north of the country, a chain of Himalayan glaciers suffer increasingly unstable rates of melting and concerns about the long-term viability of the ice in the face of global warming.

Water flows from these melting glaciers until it breaks the natural ice dams that hold it in place. That, in turn, can result in devastating floods like the one that occurred in 1994, when a torrent of mud killed dozens of people in Bhutan and wiped out entire villages. Western scientists call this phenomenon a glacial lake outburst flood, or GLOF. With 24 of its 2,674 glacial lakes considered unstable, Bhutan is preparing in the coming years for even deadlier "mountain tsunamis," as the phenomenon is sometimes referred to.

Bhutan is one of the first countries in the world to make GLOF prevention a national priority. In 2005, the government received environmental protection funds financed in part by the United Nations Development Programme (UNDP). The money was earmarked in part to help Bhutan drain water from the Thorthormi glacial lake and reinforce its natural dams. But at that high altitude, the work is difficult, dangerous and ultimately costly.

The air is too thin for helicopters to be of much use. Instead, a group of some 350 residents had to hike 10 days in order to set up a base camp at 5,000-meter elevation. From there, volunteer students, retired soldiers and traditionally-clothed villagers work knee-deep in glacial water, using the few tools they have to try and open a drain canal and build stone walls to reinforce the lake. Every year their efforts are interrupted by the arrival of winter.

"Thanks to satellite imagery, it's possible to identify the most dangerous glaciers. But it's impossible to say when or where a catastrophe will happen," says Pradeep Mool, an engineer with the International Centre for Integrated Mountain Development (ICIMOD), based in Kathmandu, Nepal.

Researchers take various factors into account when assessing GLOF risk: topography, the likelihood of avalanches that could cause a lake to overflow, how solid a glacial lake's natural dykes are and the volume of water the lake contains.

The causes of glacial floods are various and difficult to evaluate. And at high altitude, in extreme climate conditions, collecting such information can be extremely dangerous. Dowchu Dukpa, an engineer with Bhutan's Ministry of the Environment, recalls how scientists struggled to measure water levels on Thorthormi Lake. "The winds were extremely strong, and almost capsized the researchers' boat," he said.

Authorities have identified certain high-risk zones and, in an effort to save lives, prohibited construction in those areas. They now plan to set up an electronic alert system. Sensors placed in the glacial lakes will keep track of water levels. If the level quickly drops, a message will be relayed by SMS so that residents – alerted via cell phones – will know to seek shelter.

Water woes for 750 million?

Although these "tsunamis from above" may be the most immediate danger, they are not the only threat facing the people of Bhutan. As the Himalayan glaciers disappear, so too will the rivers on which the Kingdom depends. Water, after all, is the country's most precious resource. Bhutan depends on it to irrigate its fields, which support thousands of farmers, and to feed its hydroelectric plants, which generate about 40% of the country's wealth each year. Water is to Bhutan what oil is to Kuwait.

Decreasing water levels in the rivers will also have an impact on countries farther downstream, potential affecting the entire region. Members of the Intergovernmental Panel on Climate Change (IPCC) calculate that the melting of the Himalayan glaciers will cause water supply problems for some 750 million people.

Even though Bhutan is hardly responsible for climate change, it nevertheless wants to be a world leader in sustainable development. Thanks to the forests that cover 82% of its territory, it is one of the few countries on the planet to absorb more greenhouse gasses that it emits. Written into the constitution, in fact, is a commitment to keep at least 60% of its territory forested.

Says Ugyen Tshewang, who directs Bhutan's national environmental commission" "We're threatened by the melting glaciers, yet we cannot exert any pressure on the industrialized countries."

CORRECTION: Le Monde's original version of this article referred to a 2007 report by the U.N. Intergovernmental Panel on Climate Change which stated that the Himalayan glaciers could disappear by 2035. In 2010 the IPCC retracted that report, calling it inaccurate; there is no known date by which Himalayan glaciers are expected to disappear.

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