The flow Confluence of river systems of the Pskem and Koksu river basins

In the Bostanlyk district of the Tashkent region, there are highmountain breakthrough lakes located in the Pskem and Koksu rivers basin, which pose a particular danger to the downstream territories. The river system of the basins of the Pskem and Koksu rivers located in the Tashkent region is characterized by the presence of many nodes of a confluence of tributaries that form the hydrographic network of the basins of the highmountain rivers under consideration. In the event of man-made and natural emergencies, a breakthrough wave can form on high-mountain outbursthazardous lakes. The main purpose of these studies is to develop a method for the hydraulic calculation to determine the depths of flows in the confluence nodes. Based on the use of the law of conservation of momentum, a model and method for calculating the junction of open water streams have been developed. To determine the depth h2 in the main channel after the confluence point, we recommend using the well-known hydraulic methods for determining the depth of water in open channels. Determination of the depths h1 and h0 of the main flow and inflow, respectively, can be analytically obtained based on the obtained dependences (9) and (10).


Introduction
It should be noted that at present, there is the most intensive development for construction and cultivation of crops in the coastal zones of high-mountain rivers, which are susceptible to flooding when the high-mountain lakes and reservoirs located above them burst, in particular, in the Bostanlyk district of the Tashkent region.
The Gosarkhitektstroy and the Ministry of Emergency Situations have shown a certain interest in determining flooding zones, calculating the main hydraulic parameters for the passage of a breakthrough wave, which can be formed when the dams of upstream highmountainous lakes and reservoirs break through, to determine the zones of safe urban planning and make the most effective architectural and planning decisions in populated areas.
The river system of the basins of the Pskem and Koksu rivers located in the Tashkent region is characterized by the presence of many nodes of the confluence of tributaries, which form the hydrographic network of the basins of the considered high-mountain rivers.
A characteristic feature of these nodes is that there is a flow in them with a change in flow rate along the path, and channel deformations occur in the form of erosion and silting. To determine the flooding zones during the breakthrough of high-mountain lakes, it is necessary to consider all the above phenomena and find out the nature of the change in the flow depth at the confluence nodes .
The main purpose of these studies is to develop a method for the hydraulic calculation to determine the depths of flows in the confluence nodes.

Methods
With the passage of flood discharges along the river, the water flow regime along the river can be assumed to be conditionally established. For this regime of movement of the water flow, a simpler solution can be obtained.
Based on these considerations, let us consider the case of steady motion, the solution of which can be obtained in a more explicit form.
Consider the case of joining flows in prismatic rectangular channels at an angle  ≤ 90 0 ( Figure.1).

Fig. 1. Analytical model union stream
According to the studies carried out by many authors, the depth h 2 is established in the channel after the confluence, which is determined only by the flow regime available here. With a relatively large length of the channel passing the total flow, the depth h 2 can be determined using the Shezy formula, and when an uneven, planned, smoothly changing movement is established in the main channel, it is necessary to know the conditions that determine this movement to determine h 2 .
Therefore, to determine the depth h 2 in the main channel, one can use the well-known hydraulic methods to determine water depth in open channels. As for the question of determining the depths h 1 and h 0 of the main flow and inflow, respectively, analytically can be obtained based on the law of conservation of momentum for a system of material points. According to the law of change in the momentum for the calculation scheme shown in Figure 1, we compose the following equations:  In projection on the OX axis The left-hand sides of equations (1) and (2) are respectively:  In projection on the OX axis  In projection on the OY axis The right-hand sides of Eqs. (1) and (2) 2. The sum of the projections of the reaction forces of the side walls, given that the reaction forces R 1 and R 2 , R 3 and R 4 , R 7 and R 8 are equal in magnitude and opposite in direction, will be  In projection on the OX axis  In projection on the OY axis 2 cos 2 sin 2 2 sin The sum of the projections of gravity will be:  In projection on the OX axis We neglect the projections of friction forces due to their smallness.
Substituting the values of the parameters included in equation (1) and making some transformations we have: Substituting the values of the parameters included in equation (2)

Results and discussion
The results of comparisons of the experimental data of other authors and the data obtained on the basis of calculations based on dependencies (9) and (10) show their good convergence.
As calculations show, the relative error when comparing the results obtained on the basis of the obtained dependences with the data of other authors is from + 1.8 to -3.4%.
In this regard, the obtained calculated dependences (9) and (10) (9) and (10) show their good convergence. As calculations show, the relative error when comparing the results obtained on the basis of the obtained dependences with the data of other authors is from + 1.8 to -3.4%.