CONDITIONAL STOCHASTIC-ANALYSIS OF SOLUTE TRANSPORT IN HETEROGENEOUS,VARIABLY SATURATED SOILS

A method is developed for the conditional (Monte Carlo) simulation of steady state flow and transient transport from point sources in variab ly saturated porous media. It combines the geostatistical method, a li nearized approximation of the soil water tension perturbation solution , and a finite element numerical model. The method is used to investig ate the usefulness of conditional simulation for predicting solute tra nsport under a variety of sampling network designs applied to a number of hypothetical soils. Saturated hydraulic conductivity data yield th e largest reduction of conditional uncertainty in relatively wet soils with mild heterogeneities. In highly heterogeneous soils or under dry conditions, soil water tension data by themselves, taken at a samplin g density of one to two correlation scales along the expected mean tra vel path, can greatly reduce prediction uncertainty about solute conce ntration. Parameter uncertainty about statistical properties of the in dependent random variables becomes less important as the number of con ditioning data increases. However, even with a very high number of sam pling data, uncertainty of predicted concentration levels remains sign ificant.