A two‐dimensional numerical model is developed for the simulation of water flow and chemical transport through variably saturated porous media. The nonlinear flow equation is solved using the Calerkin finite‐element technique with either the Picard or the Newton iteration scheme. A continuous velocity field is obtained by separate application of the Galerkin technique to the Darcy's equation. A two‐site adsorption‐desorption model with a first‐order loss term is used to describe the chemical behavior of the reactive solute. The advective part of the transport equation is solved with one‐step backward particle tracking while the dispersive part is solved by the regular Galerkin finite‐element technique. A precondi tioned conjugate gradient‐like method is used for the iterative solution of the systems of linear simultaneous equations to save on computer memory and execution time. The model is applied to a few flow and transport problems, and the numerical results are compared with observed and analytic values. The model is found to duplicate the analytic and observed values quite well, even near very sharp fronts.

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Numerical simulations were carried out to investigate the capillary barrier effect and the wicking ability of multilayer earth liner systems. Two specific cases were studied: a two‐layer liner composed of a fine‐ over a coarse‐textured material, and a three‐layer liner composed of a medium‐textured material in between a fine‐ and a coarse‐textured material. Results of the simulations show that a quadratic relationship exists between the thickness of the fine‐textured material and the arrival time of the wetting front to the interface. At the time the wetting front reaches the interface, the width of the lateral spreading within the fine material is smaller than the thickness of this material. The lateral spreading and thickness are linearly related. The wicking ability of the different materials is more significant under relatively smaller infiltration rates and is controlled by the magnitude of the hydraulic diffusivity. For the two‐layer liner the criteria of minimizing the vertical movement and maximizing the wicking effect within the fine‐textured material conflict. A three‐layer liner satisfies both of these criteria. The results for the three‐layer system show that the medium‐textured material has more superior wicking properties than the fine material does.

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