A time-splitting technique for the advection-dispersion equation in groundwater

In this paper a time-splitting technique for the two-dimensional advection-dispersion equation is proposed. A high resolution in space Godunov method for advection is combined with the RT0 Mixed Finite Element for the discretization of the dispersion term. Numerical tests on an analytical one-dimensional example ascertain the convergence properties of the scheme. At different Peclet numbers, the choice of optimal time step size used for the two equations is discussed, showing that with accurate selection of the time step sizes, the overall CPU time required by the simulations can be drastically reduced. Results on a realistic test case of groundwater contaminant transport confirm that the proposed scheme does not suffer from Peclet limitations and always displays only small amounts of numerical diffusion across the entire range of Peclet numbers.