“…In the representation and simulation of subsurface flow and contaminant transport phenomena and the agricultural processes that affect these phenomena, there are probably as many types of models, modelling philosophies, and ways of classifying models as there are sources and types of groundwater contamination (e.g., Renard et al, 1982;Mangold and Tsang, 1991). For instance in the area of diffuse or nonpoint source pollution in agro-ecosystems, various models have been proposed that deal with different aspects of the plant-soil-climate continuum, some focused more on hydrological aspects, while others consider in more detail plant physiology or the chemistry of soilwater-plant interactions.…”