The article discusses the results of numerical studies of the flow movement with a sharp change in the parameters of the channel. Basically, the results of the study using the system of two-dimensional equations of hydrodynamics-Saint-Venant are analyzed. The divergent form of two-dimensional equations describing the movement of a water stream at a site of regulation of a channel by protective and regulatory dams is given. The influence of the length step on the results of numerical experiments is investigated numerically. Graphs of the time variation of the longitudinal velocity component behind the sudden double expansion of the channel are compiled. The flow was unsteady all the time and had the character of stationary pulsations, and the finer the grid, the richer the spectrum of these pulsations. It was noted that in numerical calculations, the time step in the calculations was always much less than the minimum pulsation period, therefore, these pulsations were not associated with difference oscillations that can arise when approximating by central differences. It is concluded that, according to the authors from the following and the present work, they collectively show that the pulsations on different grids differ significantly, the average values of the velocities are close, and thereby the solution for the average values is well converged, this shows that the pulsations are a property source equations of Saint-Venant. The applicability of the numerical model, consisting of two-dimensional shallow water equations, the vector equation of momentum conservation and the scalar equation of mass conservation, in description the flow with the presence of circulation zones, which is typical when water flows are constrained by protective-regulatory structures. 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 the laboratory experiments of G.L. Mazhbits.

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.

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.

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 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.