The paper examines the flood regime of the Amu Darya River using all available ancient sources and the results of modern observations. It is shown that over the last millennium the river has had a stable flood regime. With a high degree of confidence, this statement can be extrapolated to the period of construction of the Koi-Krylgan-kala, the main axis of which is oriented to the azimuth of the heliacal sunrise of the Pleiades, which in ancient times coincided with the May flood of the Amu Darya. In Ancient Khorezm, the May flood was of particular importance. According to modern observations, this flood is the first high-water flood of the Amu Darya after the end of the winter period. The May flood could cause significant damage to the irrigation system, so it was necessary to monitor the water level. The time of its onset, according to Biruni, corresponded to the holiday of Vakhsh-Angam, dedicated to the angel called to watch the river. In addition, the significance of the May flood is explained by the fact that it coincides with the time of irrigation works, the moment of which is determined by the vegetative cycle of crops. Keywords: archeoastronomy, Koi-Krylgan-kala, flood regime of the Amu Darya, using the visibility of the Pleiades as a flood marker. page 15Several works were devoted to astronomical studies of the ancient Khorezm monument Koi-Krylgan-kala (Vorobyova, 1967; Vorobyova, 1969; Bulatov, 1988; Mammadov, 2003). A recent study on this topic [Kolganova et al., 2014] shows that the previous results are erroneous. Until now, it was assumed that the main structure of the complex is oriented along the azimuth of 69 o, which is associated with the direction of sunrise in the middle of the time interval between the spring equinox and the summer solstice and (or) in the direction of the sunrise point of Fomalhaut (α of the Southern Fish) [Vorobyova, 1967, p. 254; Vorobyova, 1969, p. 19, 28]. Using the processing of high-precision satellite images from the Go ... Читать далее