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Issues related to the design and hydraulic calculations of the transit part of a closed tubular water supply structure of the siphon type are considered. The operating conditions of a siphon with rectangular pipes in the transition mode are estimated. Due to the formation of a hydraulic jump, the inlet section of the siphon pipes experiences increased hydrodynamic loads, leading to certain defects and destruction. The design of the siphon with two breaks along the length with a portal and a smooth inlet head or without it was modeled. As a result of modeling studies, the absence of a noticeable effect of the inlet head of the culvert on the length of the free-flow inlet section was established. It was revealed that the conditions of formation, the features of the hydraulic operation of the siphon, and the loads it experiences in the transient mode are largely determined by its design solutions. With the flooding of the inlet head, the flow of air into the pipe is hindered, and a transition mode of the second type is formed with a slight fluctuation in the water level in front of the structure upstream. The dependence of the location of the flow separation point with a decrease in the throughput of water on its value was revealed, which made it possible to obtain a graph of the dependence of the relative length of the free-flow section on the square root of the Froude number. A comparison was made with the results of studies by other authors, which showed an increase in the relative length in tubular structures of the siphon type in sections with reverse slopes at the same Froude numbers. Recommendations are given on the methodology for carrying out hydraulic calculation of tubular culverts for various purposes with minimal flow rates, and ways for further multifactorial studies of siphons on the reclamation network are indicated.

The article is devoted to the assessment and study of the Kabul river basin fed by 7 existing (Jabal-Saraj, Karga, Mahipar, Naglu, Sarubi, and Darunta) and numerous planned (including Gulbahor, Baghdara, Sarubi II, Kunar I, Kunar II, Shatut) reservoirs. The article discusses the Kabul basin's annual precipitation, land cover, and runoff. In addition, it sheds light on soil erosion and the concentration of river and reservoir sedimentation in the Kabul River Basin. Recommendations are also given for solving the problem of soil erosion and the siltation of reservoirs. There is very little data on the Kabul River and its basin due to the lack of detailed hydrological data. Most of the hydrological and meteorological posts did not function or were destroyed during the crisis in the country for about two decades, which led to little or no information on the river's hydrology during this period. Because of this problem, many organizations working in basin water management and designing new hydraulic structures face difficulties in properly planning and designing new hydraulic structures and reservoirs. As a result, most researchers, planners, and designers use old data with a limited observation period, which is insufficient for adequate design and planning of hydraulic structures and other basin development projects. Due to four decades of unrest in the country, the watersheds of the Kabul Basin have been used without any rules or management, resulting in land degradation and watershed erosion. Three main problems, namely overgrazing in rangelands, rain-fed fields, and deforestation, have caused land degradation in the basin. In addition, the situation has been aggravated by the cutting of bushes for fuel in hilly and semi-hilly areas. The basin is overpopulated, and there are many industries in the major cities of the basin, which contributes to water pollution in the Kabul river. Despite water availability, due to a lack of proper planning, the major cities in the basin cannot use the basin's water for domestic needs. In cities like Kabul and Jalalabad, people mainly use groundwater, resulting in the continuous sinking of the groundwater level. For the proper management and development of the Kabul river basin, much work needs to be done, which may yield promising results for developing the country's economy and improving the environment in the Kabul basin region.

The article presents a set of engineering measures for the reconstruction of the water sector of the Western Dvina River in the Smolensk region. The measures are aimed at preventing the negative impact of water and protecting territories from flooding and flooding, as well as at restoring the transport capacity of the river’s water sector.

The article shows the results of the analytical review of the main floating structures used in the water supply channels. It is noted that there are two classes of floating constructions: active - affecting the flow regime and changing its structure in the selected direction (floating regulators, jetting devices for changing the flow structure); passive - eliminating the adverse effect of flow ingredients on the elements of the hydraulic unit of the pumping station, without changing its structure and parameters (debris deflector, aero curtain). The basic requirements for the design of floating devices are formulated: reduction of hydraulic losses (streamlining of pontoons and fenders) increase of stability, durability, maneuverability of conditions for installation on water ensuring the water tightness of hermetic compartments, the possibility of balancing and repair, increasing functional reliability and efficiency. A fundamentally new design of the structural elements of the water supply channel has been proposed to help reduce the flow of both bottom and suspended sediments to the mainstream of the water supply channel.

The article presents the results of experimental studies aimed at developing a new damper design at the spillway structure. The analysis of the distribution diagrams of the velocities at the spillway was carried out, the results of which showed that the bottom flow velocity is higher than the surface velocity by 3–17%. According to the research results, it was found that in the second variant of the research this increase is 2–22%. The maximum values of specific flow rates in the first variant of the study in the apron varied relative to the stilling well of the lower pool within 1.5–40%, in the second variant by 2–30%. The values of specific consumption in the first variant of the study in the apron increased relative to the stilling well of the lower pool within 19–85%, in the second variant by 49–89%. According to the results of experimental studies, it was found that when passing various flows through the spillway with the option without a damper, the value of the Froude number varies in a wide range, reaching Fr = 5.0, which corresponds to the rapid movement of the flow. When installing an energy absorber at the end of each drop, the maximum value of the Froude number is Fr = 2.60. When installing a damper with the concave shape under study, it equals Fr = 1.20, which contributes to the maximum reduction in the destructive ability of the discharged flow in the downstream of the structure. As the results of the comparative analysis show, the recommended option with a concave damper works most effectively. The maximum value of the Froude number is Fr = 2.20. With such an alignment of the Froude number values, the destructive ability of the water flow at the interface of the downstream of the hydraulic structure is significantly reduced.

The article analyzes the dynamics of channel processes in the irrigation pumping station inlet channels. The field studies of hydraulic and alluvial sediment regimes in the supply channels of pumping stations are analyzed and summarized. The studies of supply channel water flow under conditions of extremely high turbidity of the flow and variability of the morphometric characteristics of the channel are presented. The conditions under which the Saint-Venant equations satisfactorily describe the channel flows in the bed of the supply channels are given. Saint-Venant's twodimensional equations were numerically implemented using an explicit finite-difference scheme. In addition, the results of calculations of the flow field in the supply channels are presented. According to the results of numerical studies, the width of the sedimentation tank was taken to be equal to the design width of the channel, and the speed of water flow in it was 0.25 m/s. The length of the sedimentation tank, ensuring the retention of sediments of the finest fraction (0.05 mm in diameter), was 1042 m. The siltation time of the sedimentation tank can be reduced by 15…20% and amount to about 15 months, considering the unevenness of the velocity distribution diagram in the horizontal plane and the trapezoidal crosssection of the clarifier. Nevertheless, the arrangement of two parallel chambers of the sedimentation tanks makes it possible to be stable for a sufficiently long time.

The article presents the results of the analysis of the deep deformations of the Amu Darya riverbed in the upper reaches of the low-pressure reservoir. The analysis of the combined transverse profiles of the riverbed in different sections of the upper reaches of the Takhiatash reservoir showed that the coastal zones are most intensively silted up. At the same time, the core zone with the highest flow rates is very weakly declared. The height of the silting layer along the length of the upper stream increases in the direction of the dam. The silting area extends upstream for a length 2-3 times longer than the length of the soundings section, which is 17.5 km. To ensure the normal operation of the hydraulic system, it is recommended that conditions should be created for a normal and stable approach of the flow to the hydraulic system, which should be ensured by maneuvering the shield holes. To do this, it is necessary to create conditions for the erosion of the left-bank spillway by increasing the water flow through the extreme left-bank discharge holes. Flushing of the upper left-bank section of the river should continue until the optimal width of the leading channel is reached, which provides the main flow of the stream in front of the structure. It is proved that the formation and development of sediment deposits on the right bank between sections 8-10 leads to a change in the flow correction and creates conditions for the formation of shoals in front of the regulator of the Kizketken channel, which can complicate the operation of the water intake zone. Therefore, it is necessary to take measures to prevent the development of the right-bank channel, and the development of the channel should go from the main channel. As shown by monitoring operating mode Takhiatash waterworks, in the Takhiatash district waterworks intensive processes the channel formation, which has a strong influence on the operational mode of the dam, especially in the operation of the water intakes flushing of sediments, skip flood costs through the shields of the dam and the stability of structures.

The paper analyzes the dynamics of planned and deep deformations on the section of the Amudarya River in the area of the damless water intake in the main structure of the Karshi Main Canal-KMC. The results of field studies of the state of the canal situation of the Amudarya River at the site of a damless water intake are studied. The course of riverbed processes in the riverbed is studied. Recommendations for improving water intake conditions have been developed. According to the results of the field survey and the study of the head section of the supply canal, the state of the Amudarya riverbed in the water intake zone was assessed. The results of surveys of the hydraulic and pumping modes of sediments of the Amudarya River in the area of the damless water intake are analyzed and summarized. The results of field studies of the canal situation of the Amudarya River in the water intake area in the Amudarya River KMC in the area of the Karshi head water intake are studied. The riverbed situation is not characterized by constant hydraulic characteristics over time for the same water flow rate, i.e. with the same water horizon marks, the flow rates may differ from each other by about half, and with the same flow rates, the horizon marks may vary up to ± 0.6 m. This is explained by the extreme instability and high mobility of the canal, and large deformations of the canal occur in a short time. The hydraulic regime of the river is characterized by a significant redistribution of speeds, depth and width of the flow. The range of their changes is within: Maximum speed >Vmax =2…5 m/s; average speed Vav = 0.5…2.5 m/s; depth H max = 4…14 m, Hav = 1…5 m; width B = 300…2000 m; slope i = 0.00016…0.0003. It is established that the characteristic feature of the river is that at a constant flow can have different average velocities depth and width, for example, when Qw = 1000 m3/s, respectively, v = 0.6…1.7m/s, B = 180…1030m, Hav = 1.1…4.3m.

The article presents the study results of changes in flow hydraulic parameters and morphometric elements of the river in the area of the main dam intake structure. A model for studying the direction of flow and other parameters of the flow in the area of the main structure for obtaining water from the Amudarya without a dam has been developed. A functional graph of the depth dependence of the expenditure on the study object was obtained. Graphs of the functional dependence of the diurnal cross-section of the riverbed on the flow depth and the variation of the flow velocity depending on the flow depth were constructed. The direction and distribution of the flow in the area of the main dam intake structure were studied.

The article discusses various types of new improved dam water intake hydroelectric systems, sedimentation facilities, sediment control devices on rivers and canals with a rational layout. The results of the analysis of studies on the use of the theory of transverse circulation and methods of artificial, active regulation of the structure of the water intake flow are presented, which has become widespread in world practice and is the main one for creating an effective design of water intake headworks for pumping stations and hydropower facilities that provide them with reliable protection from sediments. The author of the article, on the basis of numerous experimental data obtained in various countries of the world, makes a conclusion about the effectiveness and prospects of using front-type structures with more than 50% water intake. The design of water intakes of this type has been significantly improved; they can be successfully used in various conditions, including on Mountain Rivers. The author draws attention to the development of a new design of the pioneer ditch, which ensures the efficient passage of bottom sediments into the downstream of the structure, which prevents intensive silting of the reservoir basin by bottom sediments and improves the efficiency of the dam water intake.

The article discusses the results of numerical studies of the flow of the Amudarya river above the point of the damless water intake to the head structure of the damless water intake to the Karshi Main Canal-KMC. The system of two-dimensional equations of hydrodynamics-Saint-Venant is used as the basis of the mathematical model. In this work, a series of calculations of the field of currents in the river channel during low-water periods is carried out. Below are the main research results and proposals for ensuring the stable operation of the damless water intake in low-water conditions. The applicability of a numerical model composed of the equations of shallow water -the vector equation for the conservation of momentum and the scalar equation for the conservation of mass, has been proved, when describing a flow with the presence of circulation zones, which is typical when the water flow is constrained by blind dams. In this case, the solution pulsates around a certain average value, and the average length of the circulation zone behind the sudden expansion of the open flow is in good agreement with laboratory experiments. Numerical studies have shown that the device of a jet-guiding dam 150 m above the water intake gate in the CMC is more effective than when the dam is located 250 m above. In essence, dam № 2 with a length of 65 m does not affect the conditions at the water intake in the KMC at all, and dam № 2 with a length of 120 m is almost equivalent in its impact on the flow to dam №1 with a length of 50 m. Analysis of the results shows that the placement of an additional threshold in the Amudarya river bed improves the situation by raising the water level at the water intake. The threshold is flooded even at low water levels, which reduces the speed load on its body. At the same time, the threshold is located directly at the beginning of the channel, in part to protect the intake from incoming sediment, and high enough speed water glistening over the threshold in line, ensure the transit of sediment that can reduce enters the intake. Such measures will reduce the turbidity of water entering the channel. This, in turn, reduces the intensity of the silting process.

The paper presents the results of a full-scale study of the banks destruction in the middle section of the Amudarya River. The article presents the main factors of coastal destruction during floods and low water periods. Recommendations for the protection of banks from erosion are also developed. As a result of studies of the intensive local re-formation process of an easily washed-out channel, the plan for hydraulic schemes for the occurrence of local erosion of the coast both with a steady and unsteady movement in an open flow was developed.

This (article) work is devoted to one, relatively unbalanced issue of the dynamics of hydraulic structures - the determination of hydrodynamic loads on the slabs of a high-pressure spillway in a cavitating flow in the presence of erosion-free energy absorbers. Working on the implementation of these studies, the authors simultaneously studied in laboratory pulsation loads on a real structure - elements of the downstream spillway devices, below – the Kafirnigan hydroelectric complex.

Presents the results of hydraulic studies in pressureless and pressure water conduits, the results of which showed that the dependences obtained for calculating the hydraulic resistance in round pressure pipes cannot be distributed without the corresponding adjustments of pressureless channels (provided that the diameter of the pipe is replaced in the corresponding calculations with a value where hydraulic radius). In particular, it follows (and this is confirmed by the data of the corresponding experimental studies published in the literature) that in the case of pressureless channels, the pressure loss coefficient, and therefore the pressure loss, depends not only on the relative roughness and Reynolds number, but also on the shape of the cross section the channel. Moreover, if for hydraulically smooth pressureless channels this dependence can be considered to a first approximation clarified, then for channels whose wetted surface is characterized by the presence of a certain roughness, the question of its influence, as well as the shape of the channel cross section on the pressure loss, is far from roughly approximate solution. The paper also considers the general equation of fluid motion in pressureless channels and the functional dependences of the coefficient of hydraulic friction on the Reynolds number, relative roughness, and on the shape of the living section of the channel; resistance formulas are first for the simplest with respect to the cross-sectional shape of the channels (round and infinitely wide rectangular), and then for channels with a more complex cross-sectional shape. To take into account the effect (on the pressure loss) of the channel cross-sectional shape and the presence of a flow with a free surface in it, additional correction factors are introduced (using the hydraulic radius concept) as well as new dependencies and formulas for determining the hydraulic friction coefficient are given, s taking into account the influence of morphometric elements of the channel on the hydraulic resistance of the machine channels of pumping stations.

An improved hydraulic method for increasing the efficiency of operation of a damless water intake is presented. Physical picture of the movement of bottom and surface sediments during flow division in the damless water intake ABMCh (Amu-Bukhara machine channel). Analysis of the distribution of sediment along the channel of the channel showed that clay particles of suspended sediment 0.25 mm decrease from 1.30 to 0.15%. It is substantiated that the angle of the flow outlet to a greater extent influenced the formation of vortex zones at the entrance to the outlet. The size and intensity of the vortices at the inlet, in turn, determined the pressure loss, as well as the amount of sediment deposited at the water inlet, by the amount of sludge entering the outlet. The analysis of the experiments showed that the optimal threshold angle to the shore is (β = 30°, 45° 60°.; It is recommended that when setting the water intake mode it is necessary to take into account the fact that the reduction of the discharge angle to reduce the pressure loss at the inlet to the water intake, the latter is more intense carried by precipitating suspensions. It has been established that intense deformations of the Amudarya river channel occur in the area of the ABMCH water intake: Due to dredging of the channel by the dredgers, the pulp is thrown into the river channel, it turns out, as it were, storage of sediment on the right bank. This, in turn, leads to a narrowing of the river channel and siltation of the supply channel, which contributes to the movement of the channel to the left bank and complicates the intake from the river into the channel. Taking into account the complexity of the processes occurring during the division of the flow, it is necessary to consider the qualitative and quantitative aspects of this phenomenon ‘in pure form‘, without affecting the moving flow of various anti-ballistic devices. To improve the conditions of water intake and the quality of the incoming stream, an improved scheme with new structural elements is proposed.

The purpose of the article is to develop the required and sufficient conditions under which numerical methods can be used for engineering calculations and for scientific research of hydrodynamic processes in solving practical problems related to predicting the spread of pollutants in water bodies and streams. The conducted studies consisted in comparing the results of laboratory experiments and mathematical modelling, in particular the distribution of heat in a stream with different temperature in water layers was studied. To check the adequacy of the proposed numerical models, calculations were performed and comparisons were made with the results of experimental data. The obtained results allowed to determine the boundaries of the qualitative difference in the flow behaviour for different numbers of Froude and Reynolds. The accuracy of the method was also studied. A number of additional requirements for numerical models were proposed in addition to approcsimation and stability, such as requirements of conservativeness (divergence), existence of trivial solutions on grids, possibility to calculate highly unsteady, quasi-stable, pulsating and stationary flows, requirement of invariance of linearized equations, as well as the requirement of a one-dimensional scheme to be a consequence of a two-dimensional scheme. Distribution of velocities of wind currents using a three-dimensional and two-dimensional model was studied for a real object. A shallow-water bay of the Aral Sea was chosen as the object for the research. Comparison of the calculation results for both models showed that the flow velocity fields, as well as the distribution of pollutants in shallow waters, can be performed using a two-dimensional model.

The article is devoted to solving the problems of reducing the useful volume of bulk reservoirs, which is an urgent task of water management. The development of the design allows to reduce the volume of incoming sediment into the reservoir thicket is the main goal of the present work. The analysis of materials of field studies and a review of existing scientific works was the basis of the research method. The results of field studies on the study of channel processes in the downstream of the feeder channel of a low-pressure reservoir and the dynamics of their siltation. It has been established that the reservoirs accumulate only 0.3-10% of the annual river flow and the degree of annual silting of the capacity of such reservoirs is on average 0.5-2.0%. After 25-50 years, reservoirs may lose half of their usable capacity and after 40-80 years, a complete failure of operation is possible. To slow down this process in the basins of the self-leveling reservoirs, a new structure of structures developed, which ensures an even flow of water in the supply channel and maximum sedimentation of sediments in the channel, which prevents them from entering the reservoir bowl.