Mixed finite element method of a seawater intrusion problem in confined aquifers

We consider a model mixing sharp and diffuse interface approach for the seawater intrusion phenomenon in confined aquifers. The aim of this work is to introduce analyze new mixed formulation, obtained by writing problem into matrix form, introducing variable σ = R ( u )∇ representing flux tensor primal h , Φ f ) T . Here, represents depth salt/freshwater interface, hydraulic head freshwater, R(u) symmetric positive definite diffusion matrix. show that continuous well-posed. For time discretization we use semi-implicit scheme, well posed.