Hydraulic calculation of irrigation settling tanks of Amu Darya irrigation systems

¹ Karakalpak State University named after Berdakh, Karakalpakstan, Uzbekistan
² Nukus State Pedagogical Institute named after Ajiniyaz, Karakalpakstan, Uzbekistan

^* Corresponding author: ruslan_kenesbaevich@list.ru

Abstract

The Amu Darya river carries a large amount of up to 15 kg/m³ of suspended matter containing up to 85-90% suspended and 10-15% bottom sediments, which pose a serious threat to the hydroelectric power station and irrigation systems operating in its basin. In case of dam water intake, head sump tanks are provided in the composition of waterworks. So, in the composition of Right-Bank and Left-Bank, sedimentation tanks with mechanical cleaning to protect the channels were built at the Takhiatash hydroelectric complex Kaskelenskaya and Selinsky irrigation system. It is established that the hydraulic and alluvial modes of operation of these settling tanks depend on the water, alluvial, and backwater modes of operation Takhiatash waterworks. It is noted that due to low water conditions, this hydroelectric power plant operated for a significant part of the year with fully closed gates in all spans, producing intensive siltation of the upper stream. These processes led to a change in the alluvial mode of operation of the settling tanks. At the same time, due to low water and excessive design dimensions, in the first years of operation, these settling tanks were heavily silted up, the bottom mark rose to 17.2 m (above the design 165 m). Properly designed settling tanks should prevent siltation of main and distribution channels while respecting the transport capacity of the channels located below. It is proved that some well-known methods for calculating settling tanks, due to their complexity and bulkiness, cannot be used in calculating siltation modes of settling tanks under operational conditions that require simplification or finding a simpler relationship. A simple method is developed for calculating the dynamics of sediment deposition in irrigation sump tanks based on the probability of turbulent pulsation motion. Recommended: for normal operation of irrigation septic tanks, it is necessary to carry out systematic monitoring of the output turbidity and intensity of treatment, as well as water supply according to the water consumption schedule.