Interaction of basin-scale topography- and salinity-driven groundwater flow in synthetic and real hydrogeological systems

• Coupled topography- and salinity-driven groundwater flow is studied on basin-scale. Increase in salinity/anisotropy weakens the topography-driven forced convection. Permeability/dispersivity modify coupling between salt- freshwater zones. Flow salt transport are revealed separated aquifers through faults. Mixed topohaline convection evolves a basin-scale system. Salinization of has endangered e.g. drinking water supply, agricultural cultivation, groundwater-dependent ecosystems, geothermal energy thermal hydrocarbon well production to rising degree. In order investigate problem coupled basin-scale, systematic simulation set been carried out synthetic numerical model. Detailed sensitivity analysis was completed reveal effect salinity, permeability, permeability heterogeneity anisotropy, mechanical dispersivity table head concentration field pattern. It established that saline dome with slow inner formed beneath discharge zone base model due regional fresh flow. An increase salinity or anisotropy decrease variation role driven by topography, thus facilitating formation saline, dense, sluggish layer deepest basin. parameter range, affects shape saltwater less However, and/or advantage homogenization within strengthen growing relative diffusion transverse dispersion, respectively. The interaction free investigated along real hydrological section Hungary. Simulation elucidated fresh, brackish character sampled different hydrostratigraphic units revealing connection upper siliciclastic aquifer lower confined karstic faults high-salinity clayey aquitard. current study improves understanding convection, i.e. especially systems.