Abstract: Groundwater is contaminated as a result of an-thropo- genically induced perturbation of physical,chemical and biological processes occurring from soil surface through the unsaturated zone to subterranean water-bearing layer .The management of water and its dissolved organic contaminants from soil surface through the unsaturated zone to groundwater supplies requires an accurate conceptual understanding and a quantitative description of all relevant physical,chemical and biological processes and properties in the unsaturated zone.some conceptual problems and opportunities for modelling un-saturated zone water flow and solute transport processess are reviewed.Alternatives to classical modelling approaches are also outlined.