STOCHASTIC MODELING OF SOLUTE FLUX IN A HETEROGENEOUS PARTIALLY SATURATED POROUS FORMATION

A framework for the modeling of solute flux and related entities in pa rtially saturated, heterogeneous porous formations was presented by co mbining a general Lagrangian formulation (Dagan et al., 1992), relatin g the travel time moments of the solute pulse to the velocity field, w ith the stochastic theory of Yeh et al. (1985a, b) for steady, unsatur ated flow, relating the statistical moments of the velocity field to p roperties of the heterogeneous formation. First-order approximations o f the travel time covariance were derived for unidirectional, vertical mean flow in partially saturated, heterogeneous porous formations of three-dimensional structures. Hypothesizing lognormal distribution for the one- and two-particle travel time probability density functions, the effect of mean water saturation and statistical parameters of the porous formation properties on expected values, and variances of the s olute discharge S and accumulated mass M passing through a given horiz ontal control plane located at an arbitrary vertical distance from the solute source, as a function of time were evaluated. Assessment of th e uncertainty in the predictions of S and M and possible application o f the results of this investigation to assessment of groundwater conta mination hazards were discussed.