A Finite Volume Unstructured Mesh Method for Modelling Saltwater Intrusion into Aquifer Systems

Saltwater intrusion occurs in coastal areas worldwide and a theoretical investigation of its sources is crucial because dissolved salts are probably the most common contaminants in freshwater. In the case of coastal aquifers, contamination arises from saltwater invasion, caused primarily by human activities due to heavy urbanisation. Hence, there is a need to predict the location and movement of the saltwater interface to be able to protect freshwater aquifers from the possible danger of contamination. Saltwater intrusion into aquifers presents an extremely complex problem that generally cannot be solved analytically and hence, numerical methods are ideal tools for producing the simulation results. In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed.