Hydraulic mode of operation of the Takhiatash hydroelectric complex

Abstract

This topic is the design characteristics of the liquid and solid runoff of the Amudarya river in the area of the hydroelectric complex, according to which the average long-term flow of the river at the site of the hydroelectric complex is 46.5 km3, the discharge is 1470 m3/s, the maximum is 5760 m3/s (July) and the minimum is 186 m3/s (March). The amount of suspended sediment reaches 5 – 6 kg/m3, and bottom 5 – 8% of suspended sediment. The annual volume of suspended sediment is 120 million tons, and taking into account bottom sediments – 130 million tons. It is noted that due to low water conditions, the Takhiatash dam operated with completely closed gates in all spans for a significant part of the year. The authors of the article provide data comparing the actual flow rates of turbidity and backwater at the Takhiatash hydroelectric complex with the calculated ones. It is proved that sharp fluctuations in the water level in front of the dam and water intake into the canals lead to a change in the hydraulic and alluvial operation of the canals. As shown by the analysis of the river channel cross-sections in the upper reach of the Takhiatash hydroelectric complex, in the initial period of operation, there is a decrease in the level of the river bed bottom. The subsequent years of operation of the hydroelectric complex (after 1982) were characterized by the stability of the ongoing channel processes in the downstream, which is characterized by its own level and discharge regime for each characteristic year. It is noted that the operating mode for dry years, which are characterized by the fact that during periods of chronic low water the gates of the shield dam are almost completely closed and its role in regulating the level regime is almost lost. In this case, the level and flow rates are regulated mainly by end regulators in the right-bank and left-bank systems of main canals, which in turn depend on the demands of limited water consumers. Under these conditions, it is extremely difficult to regulate the water level in the headwater, since it is required to keep at a certain level of the water level. It is noted that there were no difficulties with water intakes in high-water years, and the main difficulties are associated with the passage of flood flows through the shield dam. In recent years, there has been a rapid rise in the water level in the upstream, despite all the open gates of the dam, the navigable lock and water intake structures, which are explained by the influence of the introduced ponds on the throughput of the shield dam. It has been substantiated that without any damage to the water intake during the growing season, it is possible to effectively flush the headwater with a constant decrease in the water intake coefficient below the critical value of the water intake coefficient Kv < 0.55. In practice, for the Takhiatash hydroelectric complex, this means that the flushing flow rate should be at least Q ≥ 250 – 300 m3/s. Recommended: for the normal functioning of the Takhiatash hydroelectric complex, taking into account the requirements of all water consumers and sanitary passes to the downstream, it is necessary to clearly link with the operating regime of the Tuyamuyun reservoir.