Operation damless intake of the Amudarya river (Central Asia)

Abstract

The article describes the nature of the ongoing channel processes occurring in large damless water intakes from the Amudarya-Karakum, Karshi, and Amu – Bukhara channels located in its middle course. The characteristic features of the ongoing channel processes in the area of water intake are given. Based on the analysis of the current state of damless water intake, a method for improving its operation is recommended. To solve the problems of ensuring high-quality water intake and water supply, experimental studies were carried out to determine the angle of the bottom threshold in the inlet section of the head structure in the ABMCh. The analysis of the studies showed that for the threshold angles to the shore β = 30°, 45° 60°, an increase in the angle β from 30° to 60° increases the intensity of the artificial transverse circulation formed in the flow. It is proved that this circumstance is also true for a constant angle of threshold β with an increase in the relative threshold height H rth . The bottom threshold ensures the entry of bottom sediments into the head structure of the damless water intake. The threshold height is set to 1.44 m, which is determined in comparison with the height of the beds of sediments. To prevent the entry of a large amount of bottom sediment into the head structure of a damless intake, it is recommended that the device be used especially in the inlet section of the channel. It is shown that a Karakum channel is intensively exposed to deigish. Moreover, in this process a certain sequence is traced. First, one deigish is formed, the erosion products of which create favorable conditions for the occurrence of the next deigish. So the chain of deigish “walks” along the shore. The distance between deigish, also a “step,” varies widely: from 3-7 to 15-40 m or more. Then, the remaining protrusions between the deigish are washed out, which leads to a general expansion of the channel. It has been established that deigish appears and develops in both straight and curved sections of the channel. In the latter case, they are formed mainly on the concave bank, although there are cases of their location on the convex. This means that there are corresponding conditions for its formation in both straight and curved sections of the channel. It is substantiated that the formation and intensive development of deigish are associated with the intense channel-forming activity of the flow, which manifests itself both in the process of developing channel forms and in active sediment transport. It is recommended that in order to prevent the deigish process, it is necessary to carry out water management measures aimed at strengthening the channel of the channel. The implementation of concrete cladding using modern materials to reduce losses on filtering the channel in addition to preventing deigish channel and also helps to increase the efficiency of the irrigation channel.