The Geoecological Phenomenon Due to the Absence of Conditions and Regulation of Water of the Don River

Over the seventy-year period of the Don River valley flood control with the absence of a water climatic cycle, irreversible geomorphological and biogeocenotic transformations occurred in the drainage basin. As a result of persistent avalanche sedimentation, the Don delta and the Taganrog Bay seaside became shallow. During strong east winds, the seabed near the city of Taganrog and the settlements of Port-Katon and Zaimo-Obryv is dried out over a distance of 5–10 km or more. The unique phenomenon of carp and sazan activity and accumulation in the Don River delta was noted in winter of 2023–2024. Clearly abnormal mass accumulations of valuable commercial species and their early maturation could be related to a range of factors provoked by the increased water discharge from the Tsimlyansk Reservoir. The water flow with fish along the Krivoe and Svinoe delta arms, at an extreme water negative setup, came up against a sandbar, which reflects the Don River shallowing after 1952.