This paper gives the results of the investigation of the operation of a pumping unit equipped with a frequency converter. As a rule, it is widely assumed that when changing the speed up to 50 %, the pump efficiency almost does not change, and the possibility of decrease of its efficiency is not taken into consideration when calculating the economic efficiency of the operation of the pumping unit equipped with a frequency converter. However, failure to take account the efficiency decrease may cause inaccurate assessment of the economic efficiency of the use of the frequency converter and, consequently, improper selection of the method of control of the operation of the pumping units. This is particularly important for irrigation pumping plants the operation of which is characterized by large volume of the pumpable volume and less severe requirements for provision of the water pressure required for the consumer. The purpose of this paper is to carry out experiments on a test-bed equipped with a pumping unit, parameter measuring instrument, and a frequency converter, and detection of the pattern of efficiency variation with speed. The paper presents the results of the carried out experiments, the obtained characteristic curves of the variation of different types of the efficiency at variation of the pump shaft speed, as well as their analysis.

One of the main problems in the operation of hydrosystems for various purposes is the silting up of the reservoir. Silting up of a reservoir leads to a decrease in useful capacity. And, of course, the hydrosystem's facility will not be able to fully perform its functions. This issue is particularly relevant for territories located in the arid zone with transboundary rivers, whose water resources are used for industries with different types of water consumption (first of all, irrigation and energy). The most common type of cleaning of silted reservoirs currently used is hydraulic flushing. The advantages of this method are the simplicity of the technological process; the disadvantage is the large consumption of water for washing, which is especially important in conditions of constant shortage of water resources. A method for washing reservoirs of Indian-type hydrounits is proposed. The technique considers the characteristic design features of a particular hydroelectric complex, operating experience, and field research data (sediment characteristics). The proposed technique was applied at the Ravatkhodzha hydro complex.

The water pumped by reclamation stations of the Republic of Uzbekistan contains many mechanical impurities. This negatively affects the operation of pumping units. There is a decrease in the operating parameters of the pumping unit and the associated increase in electricity consumption. Analysis of the alluvial regime of the main water sources of large pumping stations shows that the sediment concentration can reach values of 15-20 kg/m³ and, on average, up to 8-10 kg/m³ (i.e., exceed the permissible values according to the technical requirements for centrifugal pumps by 2-3 times). Based on the consideration of a two-phase liquid model (pure water and mechanical impurities) and formulas for determining the useful power, a dependence is derived to determine the magnitude of the increase in power consumption. According to this dependence, a graph of the dependence of the increase in the value of the required useful power depending on the concentration of mechanical impurities in the pumped water is constructed, which can be applied in practice during the operation of irrigation pumping stations. The results of a quantitative analysis of the influence of the content of mechanical impurities in the pumped water on the value of the pump's useful power showed that with average turbidity of the pumped water of 10 kg/m3, the overspending of electricity would be 1.75%. This is of great practical importance for the machine water lifting of the Republic of Uzbekistan (the main consumer of electricity in the agricultural sector), and the results can be used to develop an energy-saving strategy in the field of operation of irrigation pumping stations.

Riverbed processes on rivers composed of easily eroded soils differ in intensity. Therefore, deformation calculation methods are needed that take into account the characteristic features of such rivers. These features can be taken into account by introducing into the composition of the initial equations of dependencies reflecting the features of the alluvial regime and the nature of deformations. To this end, based on the analysis of existing empirical dependencies and actual data of the total erosion below the Takhiatash hydro unite (Amu Darya River, Uzbekistan), the structure and type of dependence of the transporting capacity of the stream on the main parameters of the channel and the morphometric dependence of the width of the stable channel on the average depth were selected. The proposed combined calculation method is based on the theoretical equations of deformation (Saint-Venant) and the equation of fluid motion (Bernoulli) and empirical dependencies for determining the average turbidity of the flow and the width of the channel. With the use of these equations, the calculation of the total erosion below the Takhiatash hydrounite on the Amu Darya River was carried out. Comparison of the calculation results and the actual data showed their satisfactory convergence. The proposed method can be applied to calculate channel deformations on rivers composed of easily eroded soils when regulating the flow of retaining structures.

The structure of hydraulic structures of power and water management systems includes gates for various purposes, which allow you to regulate and distribute the flow of water in channels and waterworks. Existing gate designs do not provide for the possibility of generating electricity from the water energy of the stream passing through them. In order to convert the hydraulic energy of water passing through the gates into electrical energy a new patented design of the gate is proposed which allows using micro-hydroelectric power plants with a Banki turbine to make more rational use of the hydro resources of energy and water management systems. The proposed design solves the problem of expanding the functionality of the gate and increasing the efficiency of micro-hydroelectric power plants with a reduction in its cost. Areas of application of the new design for the combined use of micro-hydroelectric power plants and hydraulic gates at hydroelectric power systems are also proposed. The technique for determining the technical and economic parameters of micro-hydroelectric power plants installed on flat gates of hydraulic structures is given, and theoretical calculations are performed, which showed that the higher the capacity of micro-hydroelectric power plants, the shorter its payback period.