Flux-based methods of characteristics for coupled transport equations in porous media

Mathematical models of transport of radioactive contaminants in flowing groundwater involve large systems of coupled advection dominated transport equations. High-resolution explicit finite volume methods, if applied to advective part of model and combined with appropriate numerical methods for diffusion-dispersionreaction part, can offer precise and monotone numerical solutions, but they require small time steps. This paper describes Flux-Based Methods Of Characteristics that are extension of explicit finite volume methods, that have no restriction on time steps and that produce numerical solutions with valid discrete minimum and maximum principle. Such particular method was implemented in software package RT (Retardation, Reaction, Radionuclides and Transport) and it was used successfully to solve large systems of coupled transport equations with different retardation factors for transport.