Groundwater is water that has drained through the soil and accumulated at depth within the deeper subsoil or in bedrock. Groundwater recharge is the process whereby the surplus of infiltration over evapotranspiration drains from the root-zone and continues to flow downward through the so-called vadose-zone toward the ground-water table (Gee and Hillel, 1988). The vadose zone is the volume of deeper subsoil, that is not as biologically active as the root-zone, where deep drainage or recharge occurs. The vadose zone is as heterogenous in nature as the topsoil it lies beneath and because of its inaccessibility is more difficult to map and hence understand the processes occurring in this part of the subsoil. In areas where irrigation is carried out extensively and over a prolonged period of time, such as the irrigated cotton growing areas of northern New South Wales, information is necessary in order to determine the amount of excessive infiltration through the topsoil and the quantity and fate of the deep draining waters through the vadose zone.