ABSTRACT
Analysis and prediction of water flow patterns in the unsaturated zone are critical to many water resources and environmental problems. Examples of such problems include infiltration, which is an important part of the hydrologic cycle encompassing the associated movement and storage of subsurface water. Soil properties are a major factor in controlling rainwater partition between infiltration and runoff as well as in controlling moisture movement. Hence, an accurate estimation of infiltration and the factors affecting it is required to facilitate a reliable prediction of runoff and subsur face moisture distribution. Another example is related to agricultural management in which unsaturated water flow needs to be considered in decision making regarding irrigation. Finally, chemical transport in the subsurface environment is greatly influ enced, under certain conditions, by flow in the unsaturated zone. Contamination may be caused by leakage from sanitary landfills or by recharge of sewage water under unsaturated flow conditions. Irrigation and rainwater dissolve and carry fertilizers, pesticides, and other chemicals under unsaturated conditions also. In most cases, un derstanding chemical transport and transformations in the unsaturated zone is essen tial for assessing the actual or potential contamination of groundwater aquifers.
