PENETRATION OF SALINE WATERS FROM THE TAGANROG BAY INTO THE BRANCHES OF THE DON RIVER DELTA (NUMERICAL MODELING ON THE EXAMPLE OF AN EVENT IN THE PERIOD FROM 23 TO 27 SEPTEMBER 2014)

The mouth area of the Don is a key area of the Sea of Azov basin, where complex processes of interaction between river and sea waters take place. Wind-induced water level fluctuations and the related inflow of transformed sea waters into the Don River delta branches are especially manifested here. Under certain hydrometeorological conditions, the salty waters of the Taganrog Bay penetrate even into the mouth of the Don River, where fresh water intake is located. The paper describes a mathematical model of the process of the salt water inflow of the Taganrog Bay into the Don River delta. The hydrodynamic component of the model is based on the equations of Saint-Venant, written in characteristic form. The transport component is described by the one-dimensional convectiondiffusion equation in the case of a conservative substance. The mouth section of the Lower Don from the village of Razdorskaya to the mouths of the Don River delta, including the Stary Don, Mokraya Kalancha, and Bolshaya Kuterma branches, was chosen as the calculation area. The problem is solved by finite-difference methods using implicit schemes. The calculations were carried out taking into account the meteorological situation in the period from 23 to 27 September 2014, when the strongest wind surge in recent years was observed. The results of calculations of the water flow rate and salt concentration in the Don branches depending on the water level in the Taganrog Bay are presented. Comparison of the calculated values of the salt concentration in the Azov port area with the observed values showed that the presented mathematical model adequately describes the process of salt water inflow from the Taganrog Bay into the main branches of the Don River. At the same time, the model gives an idea of the general trend of possible salinization of the Don River delta during surges, which can be used for prediction of such phenomena and taking executive decisions for sustainable water supply of seaside cities.

unsteady flow, salinity, mathematical model, computational experiment, surge phenomena, convective transfer