TRANSPORT MODELING IN HETEROGENEOUS AQUIFERS .1. STATISTICAL DESCRIPTION AND NUMERICAL GENERATION OF GRAVEL DEPOSITS

Transport of solutes in groundwater is decisively influenced by the he terogeneity of the aquifer. The goal of the present work is the numeri cal generation of synthetic heterogeneous aquifer models based on a st atistical description of heterogeneities in gravel aquifers. Large unw eathered outcrops in several gravel pits in northeastern Switzerland w ere investigated in this context. On the basis of sedimentological obs ervations it was possible to specify distinct sedimentary structures a ppearing as lenses or layers. All structures have been identified in e ach of the investigated outcrops. By inspecting and analyzing photogra phs of the outcrops, it was possible to estimate the probability densi ty functions (pdf) of the geometrical attributes of the sedimentary st ructures. Disturbed and undisturbed samples were taken from these stru ctures to estimate the pdf of their hydraulic properties, that is, the hydraulic conductivity and the porosity. The information obtained is used to generate distinct numerical realizations by unconditional stoc hastic simulation of synthetic aquifers having the same statistical pr operties with respect to hydraulic conductivity and porosity as the in vestigated deposits.