International audienceWater reservoirs play an important role in areas with limited and erratic precipitation where water is stored and re-distributed later for different purposes. Irrigation is primarily a major water consumer in arid countries of Central Asia for the economic development, employment and food security of the region. The major rivers of Central Asia (e.g., Amu Darya, Syr Darya, and Zerafshan) are turbid watercourses. Sedimentation reduces the main reservoir asset i.e., its volume capacity. In addition, vast territories of the region's countries have been transformed for agriculture to grow water intensive crops such as cotton, rice and wheat during the Soviet Union that dramatically accelerated soil erosion by water and wind. Thus, many man-made water reservoirs are affected by high sedimentation rates. Moreover, uneven spatial and temporal water resources and a Soviet-inherited unified hydraulic infrastructure have raised transboundary reservoir management issues over water resources allocation among the countries in the region such as Kyrgyzstan, Tajikistan, Kazakhstan, Uzbekistan and Turkmenistan. The rivers such as Syr Darya and Amu Darya are already regulated by more than 78 and 94 %, respectively and attempts for new reservoir projects upstream raises increased concerns of the downstream countries (e.g., the Rogun hydropower station in Tajikistan and the Toktogul reservoir in Kyrgyzstan). For instance, the uncoordinated use of reservoirs has caused the Arnasai lake problem in Uzbekistan with environmental, material damage and social unrest. The aim of this paper is first to review the present conditions and the role of man-made water reservoirs for irrigation in Central Asia with special focus on Uzbekistan, second to document past and current reservoir sedimentation conditions in Uzbekistan and third to discuss research carried out by Soviet and present-time local research community in the domain of erosion and sedimentation in the region
Abstract:The political transformation of the Central Asian region has induced the implosion of the interconnected physical hydraulic infrastructure and its institutional management system. Land-locked Central Asian countries, with their climatic conditions and transboundary water resources, have been striving to meet their food security, to increase agricultural production, to sustain energy sectors, and to protect the environment. The existing water reservoirs are strategic infrastructures for irrigation and hydropower generation. Upstream countries (Tajikistan and Kyrgyzstan) favor the reservoirs' operation for energy supply, while downstream countries (Uzbekistan, Turkmenistan and Kazakhstan) push for irrigation use. This paper provides an overview of the current challenges and perspectives (technical, institutional, and legal regulations) and presents recommendations for the sustainable management of man-made water reservoirs in Uzbekistan.
The paper presents results of the application of a geostatistical approach to assess the water resources availability of the Akdarya reservoir in Uzbekistan. This geostatistical approach includes a (semi-) variogram analysis and interpolation (kriging and simulations -turning bands-). Techniques predicting values at unsampled locations for generating digital bathymetric surface models of reservoir bottom conditions for calculating the volume and surface area at a given water elevation are also considered. The simulation enables to have a range of reservoir volumes and surface areas with the same probability in comparison to the kriging and traditional methods.The geostatistical approach creates digital surfaces that represent relatively accurate reservoir bottom conditions and support automated reservoir volumes and surface areas calculations. This in turn significantly reduces time, work load and financial burdens for sedimentation survey projects.
In the given article the design of service life for hydraulic structure reinforced concrete elements has been performed analytically with the use of the basic techniques and by constructing reinforced structure protective layer carbonization models, mathematic modelling methods for physical processes. The main goal of the work is to determine the service life for reinforced concrete structures of spillways and its elements under impact of the environment during their operation.
Great attention around the world is paid to the design and construction of riverbank protection and channel control structures on submountain section of rivers. High slopes (i=0,001÷0,004 and higher), flow kinetics and ability to transport large amount of sediments are the features of submountain section of rivers. Most of the research in this sphere has been conducted on the study of patterns of flow constrained by transverse structures in valley parts of rivers. The main goal of this work is to establish the physical picture of flow around a combined dam in submountian river, the through-flow part of which is made of tetrahedrons, as well as to develop a design method for flow velocity field. Formations of two regimes have been established experimentally, i.e. “calm” at ia<icr and “critical” at ia≥icr. These regimes are mainly affected by flow contraction degree na, and Froude number Fr. The presence of the following zones was established: core, intensive turbulent mixing and backflow zones, as well as the affinity of velocity fields in the zone of mixing by Shlihting-Abramovich. Prandtl has realized the task for “calm” regime with the use of integral relationship expressing law of conservation of momentum in the flow, equation for conservation of discharge and differential equation for nonuniform motion of transit flow with the account of tangential turbulent stresses on lateral surfaces. As opposed to the existing solutions, we accounted for the presence of two regions of spreading with different slopes of water surface, horizontal component of fluid weight, nonuniform distribution of velocities in head section, high roughness and the case when sections of target and vertical contraction do not match. Satisfactory results were obtained by comparing theoretical solution and experimental data.
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