AN ANALYSIS OF THE LEACHING OF CHLORIDE TRACER APPLIED TO PIPE-DRAINED PLOTS USING A COUPLED UNSATURATED SATURATED ZONE MODEL OF SOLUTE TRANSPORT

The modelling of leaching of nitrate and other solutes in artifically drained soils is complicated by the need to consider both unsaturated and saturated components of the system. This work is an attempt to couple together an unsaturated zone transport model (Addiscott & Whitmore, 1991) with a steady state travel-time model (Ernst, 1973) for the saturated zone. The model was tested using chloride leaching data from eight hydrologically isolated plots on a pipe-drained clay loam soil. Approaches to parameter estimation are discussed. Results were variable, for on some plots saturated zone travel time could be virtually neglected, whereas on other plots this component was apparently important.