Silting Problems Solution of Mountain Reservoirs' in Georgia

According to Georgia's Second National Communications to the UNFCCC (Tbilisi, 2009), at the East coast region of the Black Sea, the current Climate Change started in the beginning of the 1900's (at the period of 1900-2005). The increment of Caucasus mountain region temperature and precipitation appeared to vary in the 0, 4-0, 6°C and 6-13% respectively. Assessments of Central Caucasus glaciers, have indicated that up to the present time the total area of glaciers may have decreased by 25% and their total volume may have been reduced from 1,2 km2 to 0,8. In the result of glaciers degradation a river deposit volume is considerably increased. Climate change has strengthened also processes of sea shore abrasions and mountain reservoir' sedimentation. Two antagonistic problems are actual: Development of the hydro-power; Coastal erosion (caused by beach forming deposits deficiency). Accordingly, realization of a hydro-power problem generates a third heavy – ecological one. The harmonious decision of all three problems is possible, if the eroded beaches periodically will be artificially filled by river sediment, deposited in the reservoirs. For this purpose, it is necessary to organize a system of the quarries in a chosen reservoir. Now, the most convenient for the solution of a deposit source problem, is the withdrawing of inert material from a reservoir. For now, almost 60.0 million m3 of sediment is accumulated in it, out of which 35-40 million m3 is beach forming one. The offered method of “quarried extractions of sediment from a reservoir” has also other important advantages: as the greater volume of sediment will be removed from the reservoir so more useful water volume for hydro power will be able to accumulate in it. The proposed method will allow: periodic filling beaches with deposits; the transformation of a reservoir in a renewed a source of deposits; recommendation an optimum variant of an arrangement of the quarries system in a reservoir and to organize conveyer for delivery of deposits to the coast and other users. Thus the significant economic gain is achieved and the loss is not rendered to the environment. The basis of a method is knowledge of a sedimentation prism dynamic, which is determined by morphometry, hydrology and type of reservoir regulation. The quarries have to be located along the reservoir' length. These phases are stronger than other factors influences the distribution of deposits and reservoir dimensions (length and depth of the reservoir). Therefore, in different reservoirs the fractional structure and genesis of deposits essentially differ from each other both on the length of a reservoir, and on its depth. Hence, in view of this regularity should arrange a system of quarries and transport service. Ignoring of this regularity can cause significant financial damage, disappointment in the efficiency of a method and delay of works on preventing catastrophic erosion at Georgia's (Gonio-Batumi) coast section. Most sharply, this coastal section requires the offered methods, because according the calculations made, it will be impacted by the limit of beach forming sediment for more than 500 years. So if the appropriate measures do not begin as soon as possible the catastrophic erosion of this coastal will begin in 5-7 years, and the government will be urgently compelled to realize the results of offered research. As the user of this method can be any mountainous country (particularly tide-less one), with high hydro power potential, where the flowing into the sea, rivers are blocked by the reservoirs, for the reason of which coastal beaches are exposed of sediment' sharp deficit. The advantage of an offered method consists in that it is capable to solve harmoniously and with a serious economic gain three antagonistic problems – hydro-power, coast protection and ecology. The reality of the wide application of a modern method is determined by filling of degraded beaches and satisfaction needs of the industry on an inert material, is the most favorable river deposits withdrawn from reservoirs. Reservoirs represent renewed resources of river deposits. The constant existence of these antagonistic problems and necessity of their solution with an economic gain and without ecological damages by offering methods real and rather steady in practice. Acknowledgements. This study is funded by Shota Rustaveli National Science Foundation within the scope of grant “Modern Methods of the Joint Problem Realization for Shore Protection and Hydropower” (AR/220/9-120/14).