A numerical model for the transport of salinity in estuaries

Abstract

[Abstract]: In this paper, a numerical model for the simulation of the hydrodynamics and of the evolution of the salinity in shallow water estuaries is presented. This tool is intended to predict the possible effects of Civil Engineering public works and other human actions (dredging, building of docks, spillages, etc.) on the marine habitat, and to evaluate their environmental impact in areas with high productivity of fish and of seafood. The prediction of these effects is essential in the decision making about the different options that could be implemented. The mathematical model consists of two coupled systems of differential equations: the shallow water hydrodynamic equations (that describe the evolution of the depth and of the velocity field) and the shallow water advective-diffusive transport equation (that describes the evolution of the salinity level). Some important issues that must be taken into account are the effects of the tides (including that the seabed could be exposed), the volume of fresh water provided by the rivers and the effects of the winds. Thus, different types of boundary conditions are considered. The numerical model proposed for solving this problem is a second order Taylor-Galerkin Finite Element formulation. The proposed approach is applied to a real case: the analysis of the possible effects of dredging Los Lombos del Ulla, a formation of sandbanks in the Arousa Estuary (Galicia, Spain). A number of simulations have been carried out to compare the actual salinity level with the predicted situation if the different dredging options were executed. Some of the obtained results are presented and discussed.