Numerical simulations of topography-induced saltwater upconing in the state of Brandenburg, Germany

Saltwater intrusion from saline formation waters in the shallow lowlands of the state of Brandenburg, Germany, is simulated using a 2D density-dependent (dd) flow and transport model. Based on the geological situation and the present-day chemical composition of the groundwaters in that region, migration scenarios with and without inclusion of density effects are modelled. We find that, due to the shallowness of the aquifer system, the surficial topography has a large effect on the flow and migration patterns and, especially, gives rises to upwelling flow underneath the discharge area of the Nuthe river. Comparing models, with and without density effects included, we then investigate possible saltwater upconing due this natural discharge flow pattern. A sensitivity study of the hydrodynamic dispersion and of the anisotropy of the aquifer is at the heart of the investigation. The results of the models show that density effects are diminishing for large values of the dispersivity and high anisotropy ratios. This means that for the management of saltwater intrusion, instead of using a complicated dd flow and transport model, it may be sufficient in most practical situation to use a passive transport model, which would have a much smaller computational time.