Numerical solutions for solute transport in unconfined aquifers

Abstract

Abstract Two numerical methods for solving the problem of solute transport in unsteady flow in unconfined aquifers are studied. They are the method of characteristics (MOC) based on the finite difference method (FDM), and the finite element method (FEM). The FEM is further subdivided into four schemes: moving mesh, pseudo‐Lagrangian (FEM1); stationary mesh, pseudo‐Lagrangian (FEM2); pseudo saturated‐unsaturated, Eulerian (FEM3); and non‐stationary element, Eulerian (FEM4). Experiments on a one‐dimensional flow case are performed to illustrate the schemes and to determine the effect of discretization on accuracy. In two‐dimensional flow the above methods are compared with experimental results from a sand box model. Results indicate that for a similar degree of accuracy, the FEM requires less computational effort than the MOC. Among the four FEM schemes, FEM4 appears to be most attractive as it is the most efficient and most convenient to apply.