Modeling of variability of hydrological characteristics of the Tuzla group of lagoons under various variants of their water exchange with the sea

Abstract

The article is devoted to solving the problem of stabilization of hydrological regime and hydro-ecological conditions of the Tuzla group of lagoons located in the central part of the Danube-Dniester interfluve by ensuring and regulating their water exchange with the open sea through artificially created channels in the barrier beach that separates the water body from the sea.
 The research presents the results of adaptation of the well-known modern numerical hydrodynamic model Delft3D Flow Flexible Mesh to the conditions of the Tuzla group of lagoons, as well as the results of its application to determine the effectiveness of various variants for ensuring water exchange with the sea based on the outcomes of scenario mathematical modeling.
 In particular, the following variants of channels functioning were studied: (1) a relatively narrow connecting channel at the 2nd km of the barrier beach (near the Burnas Lagoon) together with a wide and deep outlet that existed before 2015 at the 24th km of the barrier beach (near the Shagany Lagoon); (2) a wide controllable connecting channel in the Shagany Lagoon placed on the outlet, alongside with the above-mentioned channel in the Burnas Lagoon; (3) an additional (third) narrow channel at the strip of the barrier beach near the Alibey Lagoon.
 The characteristics of the annual cycle of water salinity spatio-temporal variability were used as indicators of the effectiveness of management decisions for ensuring the stability of the lagoons' hydro-ecological conditions.
 Based on the analysis of the scenario modeling results it was concluded that the optimum solution of the problem related to stabilizing the hydro-ecological regime of the water body consists in ensuring the constant multidirectional water exchange with the sea through two artificial connecting channels in the barrier beach (both with bottom marks of minus 1.0 m (Baltic Height System) and 60 m and 15 m wide for the Shagany Lagoon and the Burnas Lagoon respectively) throughout the year. This will deny any salinization of the water body over the long term.
 For the specified variant the time of complete water renewal with sea water for the main lagoons of the Tuzla group would constitute 8 and 12 months for the Shagany Lagoon and the Alibey/Burnas Lagoons respectively.