A "random-walk" solute transport model for selected groundwater quality evaluations

Abstract

A generalized computer code is given that can simulate a large class of solute transport problems in groundwater.The effects of convection, dispersion, and chemical reactions are included.The solutions for groundwater flow include a finite difference formulation.The solute transport portion of the code is based on a particle-in-a-cell technique for the convective mechanisms, and a random-walk technique for the dispersion effects.The code can simulate one-or two-dimensional nonsteady/steady flow problems in heterogeneous aquifers under water table and/or artesian or leaky artesian conditions.The program covers time-varying pumpage or injection by wells, natural or artificial recharge, the flow relationships of water exchange between surface waters and ground water, the process of groundwater evapotranspiration, the mechanism of possible conversion of storage coefficients from artesian to water table conditions, and the flow from springs.It also allows specification of chemical constituent concentrations of any segment of the model.Further features of the program include variable finite difference grid sizes and printouts of input data, time series of heads, sequential plots of solute concentration distributions, concentrations of water flowing into sinks, and the effects of dispersion and dilution or mixing of waters having various solute concentrations.