c tmBalkema. Rotterdarn.I5BN9054t03078

University ofWestern Australia, Nedlands. WA, Australia ABSTRACT: Groundwater contamination is usually modelled using the advection-dispersion equation with a dispersivity that increases with travel distance. An alternative viewpoint is that the dispersivity is travel time dependent. The hydraulic conductivity, K, varies randomly with position so as-to change the local Darcy flux throughout the aquifer. The mean movement of a passive solu~e is the same as the mean fluid velocity. Its spread, however, is controlled by local variations in fluid flow. Given the statistics of the Darcy flux (derived from the K statistics), it is possible to predict the macro-scale dispersion that will be experienced by a solute plume moving through the aquifer. A formula for the macro-dispersion coefficient, which is a function of the solute travel time in the aquifer, is presented. The predictions of the theory are then compared with the results of a well-controlled field experiment