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LAKE SAREZ
Lake Sarez is situated half way along the Murgab River practically in the center of the Pamirs. It emerged as a consequence of a powerful earthquake on February 18, 1911, when a huge block of rocks collapsed from the right board of the Murgab River Valley. The earthquake covered a vast territory of the Pamirs and Northern Afghanistan.
The earthquake parameters
were as follows:
- Time - 18 hours 41 minutes 14 seconds (Greenwich time).
- Coordinates - latitude: 38.2 o n. l.;
- longitude: 72.8 o e. l. Magnitude - M=7.4 on Richter scale.
- Tremor intensity on the surface of the epicenter 9-10 points on MSK-64.
- The depth of the epicenter: 70-75 km.
The earthquake covered an extensive territory of the Pamirs and the north-eastern part of Afghanistan. However, the exact location of the epicenter is unknown. Instrumental record of the earthquake was made by two observatories: Pulkovo near St. Petersburg, and Potsdam, Germany.
O. E. Agakhanianz (1989) provides a description of the earthquake by eye-witnesses: "After the collapse, tremors continued for a few more days; dust settled only in three days and rocks kept falling from the slopes for fifteen more years.
54 people were killed in Usoy village, 10 in Savnob, 4 in Rukhch, 30 in Pasor, and 40 in Nisur.
The tremors rapidly faded down in the southern direction. A 6.0 point earthquake was felt in Khorog and there were practically no destructions in Ishkashim. From west to east the fading was not that fast - ice was broken at Karakul Lake and Rushan suffered from destruction."
The earthquake triggered a collapse of a huge block of mountainous rock from the right
site of the valley in front of the village of Usoy. The landslide buried the whole village and all its inhabitants except four people who were away from the village on the night of the earthquake (O. Agakhanianz, 1989). A gigantic mountainous rock with the volume of 2.2 cubic km blocked the River Murgab and formed a dam. A big lake that started to form behind the dam finally covered the village of Sarez (which gave its name to the lake) in October 1911 (according to the data provided by O. Agakhanianz, it had most probably happened in the summer of 1912). The dam itself got the name of Usoy. A smaller lake formed at the confluence of the left tributary of the Shadau River into the Murgab - Lake Shadau that is separated from Lake Sarez by a minor abutment. Twice - in 1987 and 1994 when the maximum water level in Lake Sarez was observed- the abutment was overflowed.
1914 is considered the year when filtration through Usoy dam began.
Practically immediately after the disaster, the scientific circles of Russia began discussing the question of the stability of the new dam and a probability of a catastrophic flood from the growing lake. It is worth noting that forecasts - both favorable and terrifying - were made not only by scientists and experts but also by people with little in common with the problem.
There existed two points of view with regard to the Lake Sarez problem. One of them - the newly formed dam is unstable and a catastrophic flood from the lake is a probability involving all the imaginable consequences. Another one - the Usoy dam is a natural stable formation and the lake will exist for quite a long time similarly to other conformable lakes: Yashirkul Lake in the Pamirs, Iskanderkul Lake in Central Tajikistan and many others.
Among the early investigators of Lake Sarez there are names of P. Zaimkin, G. A. Schpilko, D.D. Bukinich, I. A. Preobrazhenski, V. S. Kolesnikov, O. K. Lange, V. A. Afanasiev, V. I. Razek and many others. |
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