USE OF TENSION INFILTROMETER DATA WITH UNSATURATED HYDRAULIC CONDUCTIVITY MODELS

A new method is presented to estimate the relationship between unsatur ated hydraulic conductivity and soil-water pressure using tension infi ltrometer data. In this method, both the early transient and the subse quent quasi-steady stages of the infiltration process underneath a ten sion infiltrometer disc are analyzed. Our investigation indicates that the infiltration rate at early times closely follows the aquare-root- of-time relationship (Philip, 1969). This behavior permits the evaluat ion of the sorptivity, which is an integrated measure of soil diffusiv ity. At later times, three-dimensional quasi-steady flow beneath the i nfiltrometer disc develops, and the Wooding equation for from a circul ar pond is used to evaluate the sorptive number and the saturated hydr aulic conductivity. Simple algebraic expressions are introduced to rel ate the sorptivity and sorptive number to the parameters of the Brooks and Corey model of unsaturated hydraulic conductivity. The method des cribed here extends the utility of tension infiltrometer data to a lar ge class of hydraulic conductivity models and provides an in situ tech nique to determine suitable parameters values for these models.