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The Tuyamuyun hydro-complex on the Amu Darya River, consisting of one in-channel and three off-channel basins with a design volume of 7.8 billion m3, was intended to improve the supply of irrigation water and electricity to the Khorezm region and the Republic of Karakalpakstan and to control the catastrophic floods in the lower reaches; it was put into operation in 1984. The water reservoir complex is in joint use by the Republics of Uzbekistan and Turkmenistan. Numerous measurements showed that the useful volume of the reservoir due to siltation decreased from 2.34 billion m3 to 770 million m3, i.e. by 67%. To partially compensate for the lost capacity, it was proposed to build-up the protective levees and to erect the new dams, where the topography of the area allowed. Using the GIS, the predictive volumes to increase the capacity of the Channel water reservoir have been proposed, depending on the water level in the reservoir, which between the marks ▽130.0 and ▽131.5 amounted to 527.3 million m3. The necessity was shown to increase the height of the following protective dams: No. 1 ▽134.5, No. 2 ▽134.8, No3 ▽136.7, No. 4 ▽134.4, No. 5 ▽136.4. No. 6 ▽137.9, No. 8 ▽138.6, No. 9 ▽135 and land dam 134.8.

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The purpose of the study was to analyze the foundation's filtration strength and the HPP building's shear stability after 38 years of operation as part of the Tuyamuyun hydroelectric complex on the Amudarya River. The analysis was carried out based on field data obtained with the help of 16 piezometers installed in two alignments within the block of the HPP building and vertical drainages in the grassland. The constructed graphs of water pressure fluctuations in piezometers coincide with the nature of the change in the water level in the upper and lower pools. The actual gradients did not exceed the allowable gradient for the shaly sand interlayer and limestone bedding fracture filler. Comparison of the maximum natural gradients and those calculated from model studies using electrohydrodynamic analogies. The stability of the HPP building block is estimated by the maximum piezometric pressure and compared with analytical calculations, and the safety factor is 2.303. In this way, the base's filtration strength and the structure's shear stability are ensured in the entire range of changes in the operating mode of the pressure front of the HPP building block.

The study of the reliability and safety of the constructed earth-fill dams and the comparison with their design and calculated data makes it possible to improve the structures and methods of the calculation substantiation of these structures. This work aims to study the filtration reliability and safety of the earth-fill dam of the Channel water reservoir of the Tuyamuyun hydroelectric complex (THC) on the Amu Darya River, which was put into exploitation in 1984. Field studies were carried out according to the traditional method using results of control and measuring equipment (CME) embedded in the body of the dam. The water levels of the upper and lower reaches, piezometers, and drainage water flow were measured. The maximum water levels upstream of 130.00 were observed in July-August and November 2017, and the minimum of 117.50 at the end of March. The water levels downstream depend on the value of the discharge through the hydrosystem. The maximum level downstream for 2017 was 112.55 m (01.06.2017) with a flow rate of 2000 m3/s. The minimum level downstream of 109.15 m was observed on November 29, 2017, when the discharge into the downstream through the hydroelectric complex was 260 m3/s. A tendency to an increase in the level of the bottom downstream was found. Filling and depletion graphs of the Channel water reservoir have been built, from which it is found that they reached 2.00 m/day, and 1.60 m/day, respectively. This is 4 and 1.6 times more than the standard 0.5 m/day and 1.0 m/day. Of the 53 piezometers, 34 are working conditions; the rest do not work, require flushing. Graphs of water level changes in piezometers show that they change with an average 15-20 day delay in the water level in the Channel water reservoir. In general, the natural depression curve is below the design one. The maximum filtration flow rate was 63.3 l/s at a water level in the upper pool of 129.00.