Modeling of water turbidity distribution in the Kujbyshev reservoir

The concentration of suspended solids (or water turbidity) in a reservoir determines the transparency of water and, as a consequence, the penetration of light, the intensity of heating, as well as sorption processes and photosynthesis intensity. All this determines the importance of the study of spatial-temporal regularities of turbidity distribution during the different phases of water regime, as well as under the adverse meteorological phenomena. While it is important to monitor water turbidity and reservoir bottom reshaping, field observations in large reservoirs are often extremely difficult and expensive. In this case, numerical modeling of hydrodynamic processes in a reservoir, that describes two-phase mass transfer over the water area, may be relevant.

The object of the study is the Kujbyshev reservoir, the largest one in the Volga cascade. The mathematical modeling is based on the 3D hydrodynamic model «Wave» developed by A.V Rakhuba and integrated analytical formulas for the flow rate of sediment and the transport capacity of the flow suggested by M. V Shmakova.

It is obvious that the distribution of suspended matter in a reservoir is determined by its morphometry, the location of tributaries and runoff, the intensity of solid matter inflow with tributaries, and the meteorological conditions. Specific configuration of the Kujbyshev Reservoir and its longitudinal extension cause the uneven distribution of water turbidity and specific sediment discharge in the water area. The values of suspended matter concentration in the northern and southern parts of the reservoir vary by three or more times, and the specific sediment discharge under strong winds - by an order of magnitude.

The map of distribution of maximum water turbidity in the Kujbyshev reservoir presented in the paper is compiled under the hypothetical initiation of bottom soil agitation processes over the water area. The result is particularly valuable for the low-water period, which is characterized by the lowest depth of the reservoir, and therefore the highest values of turbidity. The resulting map of the maximum turbidity distribution makes it possible to assess water areas with the most unfavorable hydrodynamic conditions, which can become the basis for further recommendations on the activities related to dredging.

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