ABSTRACT
An essential requirement in understanding and studying contaminated water movement in the vadose zone is the characterization of hydraulic properties, especially the saturated and unsaturated hydraulic conductivity. This includes hydraulic conductivity as a function of matric potential in a partially saturated porous material. Many methods have been developed to evaluate the hydraulic properties of porous materials by in situ and laboratory procedures. However, because of the sensitivity of hydraulic properties to soil structure, in situ methods are potentially more accurate. Recently, the disc infiltrometer has become a popular device for determining in situ hydraulic properties [unsaturated hydraulic conductivity (Kwet), saturated hydraulic conductivity (Ks), sorptivity (S) and the macropore capillary length (λc)] of soil in the wet region (White and Sully, 1987; Ankeny et al. 1988; Smettem and Clothier, 1989; Hussen, 1991; White et al., 1992; Hussen and Warrick, 1993a,b) where the majority of contaminated movement occurs. Water intake is measured from a source which is carefully controlled at a constant tension within a circular interface at the soil surface. In this chapter we will discuss the use of this device for measuring hydraulic properties in the vadose zone.
