FIELD METHODS FOR DETERMINING UNSATURATED HYDRAULIC CONDUCTIVITY.

Mathematical models have been developed which describe soil water movement under point and disc sources. Results of these models suggest the possibility of estimating unsaturated hydraulic conductivity if the variables K//o and alpha in the exponential function K( psi ) equals K//o exp( alpha psi ) are evaluated. Two approaches to evaluate these parameters in the field are proposed. Method 1 involves application of a constant flux from a simple constant flow device and measuring the steady state wetted radius for two different values of flux, and Method 2 makes use of a sorptivity tube type device - with a given potential at the soil surface and measurement of the steady flow rate and wetted radii. These measurements allow for the algebraic solution of the hydraulic conductivity function.