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High mountain lakes of Kyrgyzstan with regard to the risk of their rupture

Congress: 2008
Author(s): Zbyněk Engel, Miroslav Šobr, Serguei Yerokhin
Charles University in Prague Faculty of Science Department of Physical Geography and Geoecology Albertov 6, 128 43 Prague 2, Czech Republic phone: +420 607 825 434, +420 221 951 350 fax: +420 221 951 367 email: jansky@natur.cuni.cz

Keyword(s): moraine-dammed lake, rupture risk, bathymetry, geophysical measurements, glacier fluctuations, Petrov glacier, Tien Shan
AbstractGlobal climate warming causes an intensive melting and retreat of glaciers in the majority of high mountains all over the world. This process is evident also in mountain regions of central Tien Shan. Melting water of glaciers influences changes in hydrological regime of water streams and causes overfilling of high mountain lakes basins. Dams of many lakes are very unstable and they often burst open. To determine the degree of this risk, it is necessary to analyse the genesis of lakes, to characterize the morphology of lake basins and to know the particularities of their hydrological regime. In mountains regions of Kyrgyzstan, there are now some 1500 lakes with an area of more than 0.01 km2 . Dams of many lakes are very unstable and various natural processes cause their destruction. The most dangerous lakes are in the stage of imminent risk of rupture and such event would have long reaching consequences for both population and property. There are now in Kyrgyzstan 302 dangerous lakes, out of them 15 belong to the first category. One of the lakes with high potential of drainage risk is located on the north-western slope of Ak-Sijrak massive in southern Tien-Shan. The lake named Petrova is situated in the foreground of the same-called glacier which is 69,8 km˛ large and 12,3 km long. The retreat of the Petrov glacier has continually accelerated since 1957. The rate of annual retreat had tripled within this period and within last decade it has increased up to 61,4 m/year. Meltwater from the glacier affects the stability of the moraine dam, threaten by decay of dead ice matrix. The maximum depth of the Petrov lake measured in July 2006 in front of the glacier terminus was 69.5 m. According to 2006 fieldwork the lake achieves 3.80 km2 and its volume is more than 76 million m3. The increase of the surface and volume of the lake accompanied by the decrease of stability of the dam represents an extremely dangerous situation that can end in a nature disaster of an immense extent. In case the lake bursts the washing out of a disposal site of highly toxic waste on the premises of the gold mine Kumtor run by a Canadian private company is a real threat. If this happened, the highly toxic waste containing cyanides would contaminate the large area in the valley of the Naryn River including two large dam reservoirs and it would get as far as to the area of the neighbouring Uzbekistan.
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