Design Justification of the New Structure for Earth Fill Dam Horizontal Pipe Drainage

The article discusses hydraulic carrying capacity design method for horizontal pipe drainage, consisting of separate corrugated plastic pipes, laid in the existing ones [1]. Calculations are carried out for pipes with diameters D=63, 75, 90, 110 mm, discharge characteristic K is estimated, K=f(D) relationship graph is drawn. Water section area, discharge characteristics, silting and actual velocity, water discharge as pipe filling function is calculated for the chosen diameter 110mm

Sedimentation of reservoirs in Uzbekistan: a case study of the Akdarya Reservoir, Zerafshan River Basin

International audienceThe major rivers of Central Asia (Amu Darya, Syr Darya and Zerafshan) are turbid watercourses. Thus many man-made water reservoirs are affected by high sedimentation rates. It is of strategic importance to rationally quantify available water resources in existing reservoirs to ensure a guaranteed water supply to the different water users. Recent drought years and physical deterioration of hydraulic structures urged authorities to re-estimate the water availability in reservoirs of Uzbekistan for the sustainable use of the scarce water resources and safe operation of hydraulic infrastructure. This paper presents the results after the application of a geostatistical approach to assess the water resources availability in the Akdarya reservoir of Uzbekistan. 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

Parameters of flow asymmetrically constrained by through spurs

Erosion of the banks of rivers brings enormous damage to the national economy of many countries. To combat them, various regulatory structures are being built: longitudinal dams, transverse traverse dams, watertight and permeable spurs, and combined transverse dams. Many issues of their design are sufficiently developed, including in our works, and are successfully applied. This research aims to develop a method for hydraulic flow asymmetrically constrained by through pile-type spurs. The conditions of the planned task of the ratio of the flow width to the depth of more than 6 were also observed. The degree of restriction of the flow by spurs varied from zero to one, and the installation angle of the spurs from 600 to 900. The study of the velocity field showed their similarity with the main provisions of the theory of turbulent jets. The velocity distributions in both zones of turbulent mixing are universal and obey the theoretical Schlichting- Abramovich dependence. The expansion coefficient of the jet is 0.20. Theoretical studies have obtained dependences for determining the velocity in a weakly disturbed core, occurrent flows, and the spreading regions' lengths, which determine the installation locations of subsequent spurs

Facts and Perspectives of Water Reservoirs in Central Asia: A Special Focus on Uzbekistan

International audienceThe political transformation of the Central Asian region has induced the implosion of the interconnected physical hydraulic infrastructure and its institutional management systems. Land-locked Central Asian countries with their climatic conditions and transboundary water resources have been striving to meet their food security, to increase the agricultural production, to sustain the energy sectors and to protect the environment. The existing water reservoirs are strategic infrastructures for irrigation and hydropower generation. The upstream countries (Tajikistan and Kyrgyzstan) favor the reservoirs operation for energy supply while the downstream countries (Uzbekistan, Turkmenistan and Kazakhstan) push on the irrigation use. This paper overviews the current challenges and perspectives (technical, institutional and legal regulations) of man-made water reservoirs in Central Asia with special focus on Uzbekistan

Geostatistical approach for the assessment of the water reservoir capacity in arid regions: a case study of the Akdarya reservoir, Uzbekistan

International audienceThe paper presents the results of a new geostatistical approach to generate bathymetric surface models from point measurement converted into continuous contour surfaces of reservoir bottoms in Uzbekistan. Sedimentation of reservoirs raises engineering, environmental and economical issues for the communities around the world in areas affected by a strong water deficit. Because of Uzbekistan's arid climatic conditions, and uneven spatial and temporal water resources distribution, responsive and innovative water availability assessment surveys of all major water reservoirs are required. Bathymetric surveying is a traditional method that is carried out for the estimation of reservoir volumes and surface areas of the corresponding reservoir stages in order to assess the water availability. Volume and surface area differences derived from multiple surveys of a reservoir provide storage loss estimates over time due to sedimentation. However, two main factors, such as intensive field data measurement and post data-processing, often limit the frequency of these surveys. Alternatively, innovative depth measurement technologies coupled with contouring and surface mapping programs provide automated reservoir volume and surface area calculations. This significantly reduces time, workload and financial burdens for reservoir sedimentation projects. This research proposes the use of geostatistical approach to assess the reservoir sedimentation in the Akdarya reservoir of Uzbekistan. The geostatistical approach includes (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 in order to calculate the volume and surface area at a given water elevation. The simulation enables to have range of reservoir volumes and surface areas with the same probability, in comparison to the kriging and traditional methods. This gives a real estimation of the resource availability for water operators to manage natural resources and hydraulic infrastructure in a sustainable manner

Theoretical bases for determining the velocity and suspended matter concentration in the swirling zone beyond the transverse dam

Design dependencies to determine the velocity and concentration of suspended matter in the swirling zone beyond the transverse dam in the presence of the initial section of the jet are proposed in the article, using the main provisions of the theory of turbulent jets, the scheme of dividing the flow into hydraulic homogeneous zones: a weakly perturbed core, intense turbulent mixing and reverse currents. The distribution of velocities and concentration of suspended matter (turbidity) in the zone of intense turbulent mixing are affine and obey the theoretical Schlichting-Abramovich relationships; this was substantiated by laboratory and field studies. The equations of continuity and conservation of solid matter along the flow were used to solve the problem. To establish the adequacy of the dependencies obtained, a test problem was implemented in which the velocities in the core and the depth along the flow were assumed constant. The problem was implemented for the following contraction ratios of flow nc 0,1; 0.2; 0.3; 0.4; 0.5. Tabular and graphic dependencies obtained show that with all contraction ratios of flow, the relative backflow velocities first increase, and at the end of the swirling zone, they sharply decrease. The maximum is observed at the intersection of the outer boundary of the zone of intense turbulent mixing with the protected coast and reaches m = 0.317. Comparison of the calculation results with the experimental ones shows their qualitative and quantitative agreement. The relative concentration of suspended matter in reverse currents remains practically constant along the entire length of the swirling zone. It is close to unity for all contraction ratios of flow

Water reservoirs, irrigation and sedimentation in Central Asia: a first-cut assessment for Uzbekistan

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

Kinematic parameters of flow constrained by combined dams with through part of tetrahedra in compression region

Every major river in the world consists of mountainous, foothills, and flat areas characterized by different flow regimes. The foothill areas differ in slopes i = 0.001 ÷ 0.004, flow kinetics Fr > 0.15, and the size of sediments. The riverbed is unstable, and the banks are prone to erosion. The construction of coastal protection structures requires solving complex issues related to their design. The analysis showed that most of the studies, including ours, were carried out for the conditions of lowland rivers. This work aims to establish the flow features of the foothill sections of a combined dam with a through part of tetrahedra when the ratio of the through part ℓs to the total length of the dam ℓd is greater than or equal to 0.5, i.e., ℓs/ℓd. ≥ 0.5 The presence of a satellite flow behind the through part, a weakly perturbed core, and the presence of two zones of intense turbulent mixing was experimentally established, and the universality of the velocity distribution, which obeys the theoretical dependence of Schlichting-Abramovich, was confirmed. It is once again confirmed that the dependence is on the slope of the bottom, the Froude number, the degree of constraint, and the formation of "calm" and "critical" flow modes. The nature of the level changes along the length of the compression region in the core, and the satellite flow differ from each other, and the alignments occur in the vertical compression alignment. The problem is implemented for the "calm" mode using an integral relation characterizing the law of conservation of momentum in the flow, the equation of conservation of flow, and the differential equation of uneven motion recorded for the satellite flow behind the through part of the combined dam. The presence of a satellite flow, two zones of intense turbulent mixing, and the different nature of the leveled regime of the main and satellite flows are taken into account. A comparison of theoretical solutions with experimental ones shows their similarity

Strength investigations of foundation of allocation of main structures of Pskem hydropower station on Pskem river

This paper presents the results of geomechanical studies of the siltstone massif experimental carried out in the right-bank adit at the site of the Pskem HPP dam. Primary shear experiments were carried out at 6 normal pressures on the stamp σ: 0.5 MPa; 1.0 MPa; 1.5 MPa; 2.0 MPa, 2.5 MPa, and 3.0 MPa

Determination of the time of lowering depression surface in transition zones with a smooth and instantaneous decrease in water level in reservoir

The Republic of Uzbekistan pays great attention to the development and implementation of a program for the development of hydropower based on ensuring the share of hydropower in the energy potential and the integrated development of hydropower potential. Over the last three years, hydropower plants have been built or reconstructed in more than a dozen small and medium-sized earth dams to accomplish this task. Typically, unstable filtration is observed in the body of earth dams because of deviations from the normal filling and emptying of water reservoirs. The main goal of the research is to determine the time to lower the depression surface in the Tupalang earth dam transition zones, which characterizes the intensity of unstable filtration during a smooth and sudden drop in reservoir water level. The calculations were made according to the theoretical dependences of V.P.Nedriga for two cases of smooth and sudden lowering of the water level in the reservoir, starting from the normal backed level (NBL). In the calculations, the values of the main parameters were taken to be the coefficient of water loss of the soil (0.3), the coefficient of filtration of the transition zones (9.5 m/day), and the coefficient of laying the slope of the transition zones (0.2). Calculations showed that the time of lowering the depression surface in the transition zones with a gradual decrease in the water level in the reservoir was 84.1 days, and with an instantaneous decrease in the water level during the operation of a dam with a height of 120 m 3.86 days, and during the operation of a dam with a height of 185 m 6.82 days