MODELING WATER AND SOLUTE TRANSPORT IN MACROPOROUS SOIL .1. MODEL DESCRIPTION AND SENSITIVITY ANALYSIS

A detailed mechanistic model of water movement and transport of non-reactive solute in a macroporous soil is described. One important feature of the model is that it may be run in either one or two flow domains using the same values for the hydraulic properties characterizing the soil. Water and solute movement in the micropores is calculated with the Richards and convection-dispersion equations and, in two domains, this is coupled to fluxes of water and solute in the macropores by empirical interaction terms. These interaction terms are redundant in the one-domain model, which simply reduces to the non-steady state convection-dispersion equation. A sensitivity analysis is presented showing how it is possible to identify conditions under which a macropore flow domain may need to be considered. In part II (Jarvis et al., 1991), the model is evaluated under field conditions in chloride breakthrough experiments in soil monolith lysimeters.