Two possible approaches for generalizing the kinematic wave model for deformable channels are being discussed in this paper, including the approximation in which the law of conservation of fluid mass includes erosion and sedimentation; and approximation that the fluid flow is determined by the kinematic wave equation without taking into account bottom deformations. Systematic comparison of the results of calculations of self-similar waves for different values of the change in water flow was carried out as well.

The problem of sustainable water intake in the conditions of significant fluctuations of flow rates and water level is significantly exacerbated by erosion of river beds. A typical example of such conditions is the damless water intake into the Karshi Main Canal (KMC) where the main flow of the Amudarya river continuously moves along a wide floodplain, changing the direction of currents. As a result, it is very difficult to withdraw the required volume of water from the river to the canal especially during dry years due to the high instability of currents at the entrance to the canal. Within the framework of the performed numerical studies, the conditions of flow spreading (vectors of depth-average velocities) were studied in the specific time intervals and crossings in the water intake area. The results of the study confirmed that without special engineering measures it is practically impossible to assure stable water diversion into the canal. As a preliminary solution of the problem, it was proposed to make a trench along the right bank in the area of water intake into the canal.

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 <0.005 mm increase from the inlet to the main structure of the ABMCh from 15% to 36%. Dusty particles of suspended sediment d = 0.05 also increase from inlet to G.P. ABMCh from 38% to 66%. Sandy sediment particles d = 0.05 to 0.25 mm, on the contrary, decrease from 3% to 71%, and sediment particles d> 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.

There are two main factors which prompt to look for an alternative to traditional approaches to the provision of drinking water. They are climate change and population growth. Climate change and its increasing scale are no longer in doubt. It tends to increase the frequency and intensity of droughts. Changes in average water availability in most Central Asian river basins are estimated to be drastically big for the next 30 years. And, groundwater recharge may also be affected with a reduction in the availability of groundwater for drinking water in some regions. Water use has been increasing worldwide by about 1% per year since the 1980s, driven by a combination of population growth, socio-economic development and changing consumption patterns. Global water demand is expected to continue increasing at a similar rate until 2050, accounting for an increase of 20 to 30% above the current level of water use, mainly due to rising demand in the industrial and domestic sectors. These obliging to redefine the strategy for the use of water resources to ensure sustainable drinking water supply forcing the use of all available water resources even those that were not previously taken into account, for example, off stream storage reservoirs. Research, development and innovation play an important role in supporting informed decision-making. Therefore, further scientific and engineering studies are also needed for the development of financially affordable, safe and efficient infrastructure services in the areas of drinking water supply, sanitation and hygiene and its components. The article considers a particular reservoir the bottom of which is composed of saline soils operating in regular filling and emptying and subject to significant wind effects. The research conducted allowed to find a place of water intake location which provides a minimum salt content in the water abstracted.

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.

Numerical modeling has become an indispensable tool for solving various physical problems. In this context, two fundamentally different approaches to the derivation of equations describing the motion of a liquid and the transfer of both conservative and non-conservative substances that have or do not affect the flow structure. In addition to the classical approach, in which the hydrodynamic equations of the baroclinic fluid are obtained from the Reynolds equations by introducing the assumption that the turbulent viscosity between jets is neglected, there is another approach, which is to introduce a certain scale of consideration, as well as the use of hypotheses about the magnitude of turbulent viscosity and small changes of flow characteristics along with horizontal coordinates as compared with the changes along with vertical one. Thus, there is the option to obtain similar equations allowing to numerically simulating unsteady flows with fixed boundary conditions (fluctuating streams). Also, the article discusses an approach to numerical simulation of biogenic substances as well as the chemical and biological processes in reservoirs.

The article discusses the results of numerical studies of flow movement with a sharp change in the channel parameters. The numerical study of the flow in the channels and rivers creates the possibility of a multivariate forecast of channel processes, rivers, and requires minimal expenditures. The purpose of the study is to determine the main objectives and directions of research in the area under consideration. A mathematical model and a computer program have been developed that allow solving a wide range of tasks for modelling currents in the channels of various difficulties, taking into account daily regulation. This makes it possible to identify and proactively take measures, such as: determining the time to reach the flow along the channel; the establishment of water volume flow in an arbitrary channel; taking emergency measures to regulate the incoming residual volume of water after its termination into the system, in the event of an accident at pumping stations; identification of the nature and direction of channel processes; prevention of undermining of supports and damage to power lines passing through the channel, and many other engineering tasks. The developed tested mathematical model allows in real conditions and in real time to help the operational services of large channels in the operational management of actions, in emergency situations, and the choice of the most effective, at any point in time, measures to minimize the consequences. Analysis of the results of many researchers has created the opportunity for the authors of this article to conclude that the above system of hydrodynamic equations is applicable in mathematical modelling of motion, taking into account the transverse circulation of the flow.

The presence of ongoing climate change and their increasing scale have now become apparent. Climate models provide a glimpse of the future. Disappointing forecasts pushing to develop models that would allow rapidly develop measures for adapting to unavoidable environmental conditions and to mitigate impacts, including those related to the deterioration of water quality in natural water bodies and reservoirs. The most simple and effective models for fast and fairly accurate forecasts regarding waters are the zero-dimensional models. Such models widely used in engineering practice owing to their considerable simplicity which is correct for conservative substances. At the same time, additional limits should be taken into account while forecasting water quality involving nonconservative components which could change its chemical characteristics in particular. The period during which the concentration of a substance becomes the same over the entire area of a reservoir could be considered as a time scale in which zero-dimensional equations are applicable, the average concentration of substances for the entire body of water can be considered only as of the average over some time not less than determined by the scope of consideration. The expression which is given in the paper allows identifying limits of applicability of zero-dimensional equations for a non-conservative substance concentration as a function of time scale and coefficient of non-conservativeness.