Astochastic Model for Solute Transport in Macroporous Soils

A stochastic, physically based, finite element model for simulating flow and solute transport in soils withmacropores (MICMAC) was developed. The MICMAC model simulates preferential movement of water and solutes usinga cylindrical macropore located in the center of a soil column. MICMAC uses Monte Carlo simulation to represent thestochastic processes inherent to the soil-water system. The model simulates a field as a collection of non-interacting soilcolumns. The random soil properties are assumed to be stationary in the horizontal direction, and ergodic over the field.A routine for the generation of correlated, non-normal random variates was developed for MICMACs stochasticcomponent. The model was applied to fields located in Nomini Creek Watershed, Virginia. Extensive field data werecollected in fields that use either conventional or no-tillage for the evaluation of the MICMAC model. The fieldapplication suggested that the model underestimated the fast leaching of water and solutes from the root zone. However,the computed results were substantially better than the results obtained when no preferential flow component wasincluded in the model.