<P> In the Himalayas, glaciers are melting and retreating, which produces 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 . </P> <P> In the past two decades GLOF has become a topic of intense discussion within the development community in Nepal . The Dig Tsho GLOF on 4 August 1985, completely destroyed the nearly completed Namche hydropower plant and all bridges, trails, cultivation fields, houses and livestock along its path to the confluence of the Dudh - Koshi and the Sun - Koshi rivers over 90 km (56 mi). 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 . </P> <P> Studies of the glaciers and glacier lakes were carried out in 1988 by a joint Sino - Nepalese team . The Arun - Koshi river basin hosts 737 glaciers and 229 glacier lakes, out of which 24 lakes are potentially dangerous . The Sun - Koshi basin is home to 45 glacier lakes, of which 10 are potentially dangerous . According to a Sino - Nepalese study, since the 1940s on at least 10 occasions, glacier lakes burst their dams . Among them were five bursts in three glacier lakes in the Arun River Basin and four in three glacier lakes of the Sun Koshi River Basin . </P> <P> The National Flood Control Policy in 1954 (following the disastrous floods of 1954 in a large part of the Koshi river basin) planned to control floods through a series of dams, embankments and river training works . The Kosi project was thus conceptualized (based on investigations between 1946 and 1955), in three continuous interlinked stages--the first was a barrage to anchor the river that had migrated about 120 km (75 mi) westward in the last 250 years laying waste to a huge tract in north Bihar and to provide irrigation and power benefits to Nepal and India . The second part was to build embankments both below and above the barrage to hold the river within the defined channel . The third part envisaged a high multipurpose dam within Nepal at Barakshetra to provide a substantial flood cushion along with large irrigation and power benefits to both countries . This was followed by the Kosi Agreement between Nepal and India signed on 25 April 1954 and revised on 19 December 1966 to address Nepal's concerns . Further letters of Exchange to the Agreement between the two countries identified additional schemes for providing benefits of irrigation . While the first two parts of the plan were implemented by the Government of India, the Koshi High dam, the linchpin of the whole plan, for various political reasons has yet precluded any action for several years but has since been revived under a fresh agreement, in a modified form for further investigations and studies (1, 2, 3, 4 & 5). </P>

Yamuna ghagra and kosi are important tributaries of which river