ICIMOD shares results of glacial lakes studies

22 Feb 2010

   TwitCount

Besishahar, Lamjung and Kathmandu

The International Centre for Integrated Mountain Development (ICIMOD) is sharing the results of recent field investigations of Thulagi glacial lake with the local community and other stakeholders at a one-day workshop on ‘Sharing of knowledge on Thulagi glacial lake’ on Monday, 22 February 2010 (10 Falgun 2066 B.S.) being held in Besishahar, Lamjung District, Nepal. Stakeholders, partners, and representatives of government and non-government organisations are taking part in the workshop.

Thulagi glacial lake was identified as one of six potentially dangerous glacial lakes in Nepal in a recent desk study carried out by ICIMOD in early 2009 with support from the World Bank (the others being Tsho Rolpa, Imja, Thulagi, Lumding, Lower Barun, and West Chamjang). This study mapped glacial lakes as well as assessing the downstream flood risk and vulnerability in the three river basins in the Nepal Himalayas.

The detailed field investigations were carried out in collaboration with national partners to discover the actual situation on the ground of three of the potentially dangerous lakes: Imja (Dudh Koshi basin), Tsho Rolpa (Tama Koshi basin), and Thulagi (Marshyangdi basin). The teams assessed the stability of the natural moraine dams, the behaviour of the mother glaciers in contact with the lakes, the volume of water stored in the lakes, and potential factors that could trigger an outburst of the lake (GLOF). They analysed the locally available hydro-meteorological data, prepared computer models (maps) of the potential flood risk following a dam break, and assessed the downstream vulnerability.

As the local communities are generally those most at risk, the information is being shared directly so that people concerned can plan accordingly. One of the most important findings of the teams was that the three lakes studied do not pose any immediate risk. Most glacial lakes actually offer considerable benefits for the local communities and should not simply be seen as a threat, but rather as a resource that needs proper care. The workshop in Lamjung will be followed by similar workshops for the communities close to the Imja and Tsho Rolpa lakes.

[Some additional information on the glacial lakes in Nepal, and details of the field study lakes, is attached.]

For further information contact:
Ms Nira Gurung
Communications Officer

ICIMOD

GPO Box 3226, Kathmandu, Nepal

email: info@icimod.org, ngurung@icimod.org

Glacial Lakes in Nepal

Glacial lakes form when a glacier retreats leaving the debris mass at the end of the glacier – the end moraine – exposed. The moraine wall can act as a natural dam, trapping the meltwater from the glacier and leading to the formation of a lake. The moraine dams are composed of unconsolidated boulders, gravel, sand, and silt. As with landslide dams, they can eventually break catastrophically, leading to a glacial lake outburst flood or GLOF. GLOFs have the potential to cause extensive destruction in the downstream valley.

GLOFs have been recorded in many different parts of the world, sometimes under other names. In 1941, an outburst flood destroyed the city of Huaraz in Peru killing 4,500 people. An outburst from a glacier-dammed lake in the Swiss Alps in 1968 triggered debris flow and caused heavy damage in the village of Saas Balen. On 4 August 1985, an outburst flood from Dig Tsho totally destroyed the nearly completed Namche Small Hydel Project and caused extensive damage farther downstream. Fourteen GLOF events have been recorded in Nepal, and another ten events where the outburst occurred in Tibet (China) but affected downstream communities in Nepal. On 11 July 1981, an outburst flood from the Zhangzangbo glacial lake in China caused extensive damage up to 50 km downstream into Nepal.

Altogether some 1466 glacial lakes were identified in Nepal in a desk study using remote sensing data carried out in 2009; six of these were considered to be potentially dangerous. The outburst of such lakes depends upon the physical characteristic of the dam, the size and depth of the lake, and its surroundings. As glacial lakes are increasing and expanding rapidly, the issues of GLOF risk assessment, early warning systems, and mitigation measures to reduce the impact have becoming ever more important.

At the same time it is important to realise that glacial lakes may offer considerable benefits to local community. They can provide a natural storage facility for water as water supplies becoming increasingly scarce, they are a focus for tourist activities, and they often have a high cultural significance. Thus they need to be looked after and managed in a controlled way that reduces any threat while helping the potential benefits to be realised. 

Formation and growth of glacial lakes needs to be monitored on a routine basis as the situation is changing yearly. In order to assess the potential GLOF risk in Nepal in particular, and the Hindu Kush-Himalayan region in general, ICIMOD is implementing a project on ‘Hazard Assessment and Mitigation Study of Potential GLOF Lakes in Nepal’ to develop recommendations for adaptation to and mitigation of GLOF hazards from potentially dangerous glacial lakes in Nepal, and to assist Nepal in the development of an overall strategy on how to address risk from GLOFs in the future.