Keywords: reservoir, volume of internal water exchange, water level, transportation time, 90Sr

Given that the hydrodynamics of internal and external water exchange in reservoirs creates fundamentally different living conditions for hydrobionts and significantly affects water quality, the task of separating the volumes of internal and external water exchange arises. The aim of the study is to obtain estimates of the magnitude and variability of internal and external water exchange in the Kyiv reservoir depending on the reservoir level. The research method is full-scale modeling, which consists in observing the dispersion in space of a certain passive conservative admixture (tracer) artificially introduced into the flow. As a tracer, we propose 90Sr, which by its properties almost meets the requirements for a tracer substance. The data of hydrological and toxicological monitoring in 1990-1991, 1993-1994 and 1998-1999 were used. Based on the data on 90Sr inputs to the upper reaches of the Kyiv Reservoir in 1991, 1994, and 1999, which had the character of sharp spikes, and the data on 90Sr concentrations at the outlet of the Kyiv Reservoir, the values of transport time and volumes corresponding to the time of contamination transport to the outlet of the reservoir were established. Guided by the transportation time and data on water consumption in the reservoir, calculated by the balance model, the values of the volumes of internal and external water exchange, as well as the parts that these volumes makeup of the total volume of the reservoir, were obtained. An interpolation of the dependence of the internal water exchange volume on the level of the Kyiv reservoir was constructed. The results obtained are in good agreement with some results obtained with the hydrodynamic mathematical model using the full-flow method by another group of researchers. The dependence of the volumes of internal and external water exchange of reservoirs on the reservoir level can be used to determine the time of pollution transportation along the reservoir, for environmental assessments and forecasts related to the study of water quality conditions.

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