Scale-dependent heterogeneities in the Gorleben area and implications for model studies

The Gorleben salt dome is located near the community of Gorleben in the northeastern part of Lower Saxony Germany. During the field investigations the existence of heterogeneities on various scales has been verified. These heterogeneities predominantly reflect the differences in the lithology of the sediments. The density of the groundwater, which is a function of salt concentration, also varies spatially. The change in groundwater density has to be considered together with spatially variable hydrogeological parameters because it has considerable influence on groundwater movement and contaminant transport. Spatial connectivity models based on information from borehole logs were developed using geostatistical methods. Different approaches for using soft information as input for these methods are evaluated. Models are used to calculate regional groundwater movement and the characteristic trends of the main flow paths under freshwater conditions. Deterministic and probabilistic uncertainty and sensitivity analyses have been performed based on groundwater, flow paths, and nuclide transport calculations using a two-dimensional freshwater model. (R.P.)