Influence of heterogeneity on the flow in unconfined aquifers

This note deals with the way the heterogeneity of the hydraulic conductivit y affects the behaviour of an unconfined aquifer at the local scale (Dagan, G., 1986. Statistical theory of groundwater flow and transport: pore to la boratory, laboratory to formation, formation to regional scale. Water Resou r. Res., 22, 120-136.). The vertical wall dam problem has been considered a s an example of this kind of aquifer and the flow corresponding to differen t piezometric head gradients and statistical characteristics of the hydraul ic conductivity space distribution has been investigated. The consequences on the free surface position and on the total discharge have been analysed, and their statistical distributions have been evaluated. Moreover, the ave rage values have been used to investigate the value of the effective hydrau lic conductivity for two-dimensional motions with significant curvatures of trajectories and a high variance of heterogeneity. The Monte Carlo method has been used, and the delicate numerical aspects, r elated to the coupling between the generation of random fields and the corr esponding free surface flow field simulation, have been thoroughly examined . (C) 2000 Elsevier Science B.V. All rights reserved.