Glaciers, Glacier Lakes and GLOF
In the Himalayas, glaciers are melting and retreating, which results in formation of lakes insecurely dammed by ice or moraines. These dams are at risk of breaking, causing a Glacial Lake Outburst Flood (GLOF) with flows as great as 10,000 cubic metres a second. Such floods are likely to destroy communication systems and various infrastructures like bridges roads, hydropower projects, foot trails, villages, fields and terraces, irrigation canals, and could cost hundreds or even thousands of lives. Such floods also transport huge amounts of sediment.
In the past two decades GLOF has become a topic of intense discussion within the development community in Nepal. Studies of the glaciers and glacier lakes were carried out in 1988 by a joint Sino-Nepalese team. In the Arun-Koshi river basin, there are 737 glaciers in Tibet and 229 glacier lakes, out of which 24 glacier lakes are potentially dangerous. Similarly, there are 45 glacier lakes in the Sun-Koshi basin, out of which 10 are potentially dangerous.
The Dig Tsho GLOF on 4 August 1985, completely destroyed the nearly completed Namche hydropower plant and also all the bridges, trails, cultivation fields, houses and livestock along its path to the confluence of the Dudh-Koshi and the Sun-Koshi rivers at a distance of 90 km (56 mi) from the Dig Tsho glacier. The Dig Tsho glacier is on the terminus of the Langmoche Glacier. This event brought into focus the seriousness of such events and the studies to assess the glaciers, glacier lakes and GLOF followed.
According to a Sino-Nepalese study, since the 1940s, there have been at least 10 cases of glacier lake outbursts within the basins investigated. Among them there have been five bursts in three glacier lakes of the Arun River Basin, and four in three glacier lakes of the Sun Koshi River Basin.
Read more about this topic: Kosi River
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—W.H. (Wystan Hugh)
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