International Scientific-Technical Conference Kokhi Vakhdat, Dushanbe City, Tajikistan
«Lake Sarez – 100 years of existence, the solution of existing problems
and ways of rational use of its water resources”
September 27-29, 2011
International Scientific-Technical Conference
Kokhi Vakhdat, Dushanbe City, Tajikistan
Regretfully, I could not take part in the Conference and represent my three reports prepared specially for reading them there. But you have a possibility to familiarize with these reports at my personal website: www.sarez-lake.ru in the Section “Reports at Scientific Conferences”. At the same website one can find the Chapters from the Monograph “Sarez Catastrophe: Geophysical Prediction”.
In spite of multi-year history of studying the Lake Sarez region, according to the modern standards, it remains still poor-studied. The basic reason for this lies not so much in its remote location, but in absence of ahead-performing geophysical investigations for compilation of maps on the scales of 1:200000, 1:100000 and 1:25000. Some detailed areas were investigated by geologists on the scale of 1:5000 from the surface, by means of geophysical methods – on the scale of 1:10000 or by single profiles. Though for higher geological effectiveness of investigations they should be studied also on the scale of 1:5000, and some of the most problematic areas – on the scales of 1:2000 and 1:500. Actually not studied by geophysical methods is the water area of the lake. And as geological works were not performed there, this area represents a “white spot” on all the maps. Also no seismic zoning of the lake region and no micro-seismic zoning of the spring sites were carried out.
By the current understanding, appearance of a catastrophic flood may be caused by the following reasons:
– collapse of the Right-Bank Landslide into the lake, which can lead to water flowing over the lowered part of the dam and cause a water outburst through it;
- collapse of secondarily generated landslides from the left-hand bank of Lake Sarez, which can cause similar consequences;
- colmatage process (plugging of holes) of the dam’s upper slope, which every year causes a water rise in Lake Sarez;
- the colmatage process can be considerably intensified by hemogenic meramixis, which must appear with time in Lake Sarez; due to the large incline of the lake banks and bottom, precipitation from salted soils of the drainage area will favor accumulation of the dissolved ions in the near-bottom area and appearance of slime fluxes; the progressive meramixis can create with time insomuch stable hemocline, that the slime fluxes will spread above it, expanding the colmatage zone of the Usoi dam’s upper slope from the bottom to the surface, which will accelerate the water level rise in the lake;
- presence of ice in the dam body (the size of which is from 20000 to 50000 m3, and this size was determined by visual overlook of the dam without carrying out special geophysical investigations for mapping); with appearance of a surface aquifer the ice will melt causing formation of new near-surface ways of filtration ;
- collapse of two weakened rock areas with a total volume of 0.7 m3 (detected in 1988) from the height of 1500-2000 m onto the lowered part of the slide dam in the disrupted niche of Usoi dam can lead to unexpected consequences;
- seismic impact from an earthquake or landslide collapse in the Usoi dam niche, which can block the ways of water filtration and cause a catastrophically quick water level rise in the lake.
The above-listed hazards are studied far from being enough. More deeper is investigated the Right-Bank Landslide. Its size is 1.25 km³, the average vertical thickness is 250 m. In the slope upper part the landslide body is torn from the entire massif by means of granite intrusion of Paleogene age. The landslide is displacing along the roof of dense monolithic rocks. With collapse of the Right-Bank Landslide into the lake the volume of overflowing wave will amount to 100 mln. m³/sec with the wave height in the lake equal to 110-150 m. By data obtained by the USA Military Engineering Corpus, the wave height (at the volume of the Right-Bank Landslide equal to 0.9 km³) above the river channel in the area of Barchadiv will amount to 155 m. Even with the minimal discharge of River Amu-Darya during a low-water period the additional water discharge equal to 17708 m³/sec (in the hydro-post Kerki) will create in the Amu-Darya lower courses a gigantic catastrophic flood which has never happened in the update history. Below the Usoi Dam a mud flow, highly saturated with hard rock materials, will appear. The water level in River Bartang will rise by 70-100 m. This will cause a collapse of mass rocks into the flow of loose fragmental material and landslides. In the area where Bartang inflows into River Pianj, the mud flows will beat against the left-hand steep Afghan shore of River Pianj, turn to the left, upwards Pianj River and stop. From the hard rock material a “mudflow dam” will be formed, which will block River Pianj for some time and, as a result, a dammed lake will be originated. Even at a minimal height of the mudflow dam, after the outburst of it, the second flood in the Amu-Darya lower courses will be much more destructive. With a maximal height of mudflow dam the town of Khorog will be flooded and ruined completely. With water outburst of the slide dam, the water discharge in the measuring hydro-post Kerki will sixfold higher than with the first wave over the Usoi Dam and twelvefold higher against the maximum value confirmed by documents. The second flood in the Amu-Darya lower courses will much more destructive. If during the floods in the beginning of the last century the maximal displacements of the channel were equal to the first kilometers, then during the given flood they can reach the first tens of kilometers. With outwash of the outburst hole in Usoi Dam, when the water discharge will reach maximal level and in the measuring hydro-post Kerni it will be the same like in the outburst hole, equal to 30000 m³/sec, in the Amu-Darya lower courses the third flood will happen.
As the result of Sarez catastrophe, the highway Dushanbe-Khorog (in the sites where it runs along the Pianj shore) will be destructed. All the bridges across the rivers of Pianj and Amu-Darya will be ruined or become unusable due to the channel displacement. The railway communication between Tajikistan, Turkmenia and Uzbekistan will be interrupted. It will be reasonable to start recovery works only after the third flood, i.e. not earlier than in a year after the catastrophe begins.
Possibilities of route and aero-visual investigations in the Lake Sarez area have been exhausted long ago. To carry out mining and drilling works is fantastically expensive. In such conditions the geophysical investigations represent the basic technique to obtain geological information on the structure of this region. In the past, by the reasons, not depending on me, the geophysical investigations in the Sarez Lake region were fulfilled in the insufficient volume. But the results of geophysical investigations, obtained with large difficulties since 1997, are not used. The geologists, studying the geological data of 1967-1991 during the period since 1997 till presently, do not understand them absolutely. The basic reason for this is that these data should be generalized by a professional geophysicist, treated with up-to-date computer technologies and translated into the geological language. And nobody better than the executer of field works, can do it. I addressed to different authoritative agencies, to the Representatives of Tajikistan, Russia and international organizations with a request to finance me for carrying out these works. I did not find understanding. All these addressings can be found at my website in the Section “Sarez Correspondence”.
I possess the unique geophysical information. I have processed a considerable part of these information at the account of my own money and, naturally, I would like to compensate the expenses. In order to complete the processing and to publish the Monograph, I need sponsors. Such potential sponsors may become the World Bank, OBSE and other international organizations.
The Monograph is necessary for geologists and hydro-engineers. But in order other geophysicists could continue investigations in the Lake Sarez area, it is necessary to have a generalized report with detailed description of technology of works and methods of their processing. The fact is that the investigations have been carried out on analog equipment. But in 1980s-1990s of the last century a computer revolution has happened and presently the Higher Educational Institutions are preparing geophysicists only for work on digital equipment and computer-aided processing of obtained data. They have no understanding of analog devices and manual treatment of information. Therefore such report is necessary. The special value of geophysical materials of 1975-1991 lies in that this is the first cycle of studying the Usoi dam and Right-Bank Landslide. Repeating of the geophysical measurements on the same profiles will make it possible to estimate changes in the elastic, strength and density properties of rocks which happened during the past period.
I welcome all the participants of the Conference!
Head of the Pamir Hydrogeophysical Team,
Southern Geophysical Expedition, PO “Tajikgeologia”,
since 03.05.1967 till 31.05.1994
September 26, 2011.