SALTFRES: a mixed finite element model for 3-D variable density groundwater flow and contaminant transport code

The SALTFRES code is based upon a three-dimensional coupled finite element, finite difference model. It simulates saltwater intrusion in single and multiple coastal aquifer systems as well as flow of saline water with either a confined or phreatic top aquifer. The code is an extension of the PTC (Princeton Transport Code) software developed at Princeton University. The numerical algorithim involves discretizing the domain into approximately parallel horizontal layers discretized by finite elements. The layers are connected vertically by a finite difference discretization. This hybrid coupling of the finite element and finite difference methods provides the opportunity to apply a splitting algorithm. During a given time iteration, all the computations are divided into two steps. In the first step, each layer of the horizontal two dimensional finite element equations are solved separately. In the second step, the one-dimensional vertical equations which connect the layer, are solved using a multi-level finite difference algorithm.