AN ITERATIVE GEOSTATISTICAL INVERSE METHOD FOR STEADY FLOW IN THE VADOSE ZONE

An iterative geostatistical inverse approach is developed to estimate conditional effective unsaturated hydraulic conductivity parameters, s oil-water pressure head, and degree of saturation in heterogeneous vad ose zones. This approach is similar to the classical cokriging techniq ue, and it uses a linear estimator that depends On covariances and cro ss covariances of unsaturated hydraulic parameters, soil-water-pressur e head, and degree of saturation. The linear estimator is, however, im proved successively by solving the governing flow equation and by upda ting the residual covariance and cross-covariance functions in an iter ative manner. As a result, the nonlinear relationship between unsatura ted hydraulic conductivity parameters and head is incorporated in the estimation and the estimated fields are approximate conditional means. The ability of the iterative approach is demonstrated through some nu merical examples.