The study of the patterns of change in the hydrodynamic parameters under the conditions of non-stationary flow at the entry of the cylindrical pipe and the initial arbitrary distribution of velocities in the entry section was conducted based on the boundary layer equations. A boundary problem was formed under the axisymmetric change conditions in the flow. The boundary conditions were chosen in accordance with the pattern of an arbitrary distribution of velocities in the entry section. A general solution of the approximating Navier-Stokes equations is presented depending on the initial conditions and the Reynolds number. In accordance with the type of flow, the boundary conditions of the problem are established, and the boundary-value problem is formulated. Regularities for the change in velocities lengthwise in the entrance region have been obtained for a constant and parabolic velocity distribution in the inlet cross-sections. Analytical solutions have been obtained, allowing to obtain patterns of changes in velocities and pressures toward flow at any section and at any time. For the mentioned cases, the composite graphs of velocity changes in different sections along the length of the entrance transition area were constructed by computer analysis, for different time conditions. With the obtained composite graphs, the patterns of change over the entire length of the transition area of the entrance region were constructed, enabling to obtain fluid flow velocity at any point of the section. The length of the transition zone can be estimated based on the condition of reaching a certain percentage (99%) of the maximum velocity of the flow. The proposed solutions create the conditions for correctly constructing separate units of hydromechanical equipment

The volume of sediment accumulations in the upstream reach of the dam and the selection of an efficient flushing measurse are determined by the accurate hydrological regime assessment that is made when designing run-of-river structures. In the Tartar River's water intake head sedimentation regime was investigated, the potential accumulation volumes on the dam's upper side were calculated, and a functional design for the deposited sediment flushing unit’s operation scheme was developed. Due to the lack of necessary data, the flow rate in the Tartar River water receiving head was measured using three parallel methods that were discovered through research on local watercourses. A comparative analysis of three sediment flow values was done and its calculated value is defined, on the basis of which the annual volume of sediment subject to accumulation in front of the dam of the head and the possible infilling size of the sediment in the upstream reach was determined. The rational placement of the outlets for flushing deposited sediment is shown while taking into account the volume of deposits, the geometric properties of the head, and its upstream reach.

The accumulation of sediments in reservoir is always a problem. Over time, these accumulations occupy the volume meant for water management, dramatically reducing the reservoir's effectiveness. The environment of the river basin below the reservoir undergoes significant changes. In this regard, assessing changes in volumetric W-H characteristics, particularly in reservoirs built on high turbidity rivers, is critical. The Mataghis Reservoir on Tartar River was chosen as the object of study. The quantity of accumulated sediments was established by original measurements and was calculated in three hydrologic ways at distinct stages of operation. The actual graphs showing the reservoir's W-H volumetric characteristics were made two decades after commissioning and are still in use. According to the findings, over 70 per cent of the reservoir volume has been filled with sediments over the course of the reservoir's thirty-year operation. A theoretical model of the sediment buildup process in basins has been created. Separate parameters have been created for the deposition of bottom sediments entering the reservoir and suspended particles in the flow. Based on them, the patterns of distribution of accumulated sediments according to the length and height of the reservoir were drawn out. The vertical pulsation velocity and the results of studies for determining the minimum rate of soil particle flow were used. To solve sedimentation problems in operating and newly constructed reservoirs, a methodology for evaluating changes in the amount of collected water and changes in the volume of water control, as well as a theoretical method for projecting their future behavior, can be applied