Salty groundwater flow in the shallow and deep aquifer systems of the Schleswig–Holstein area (North German Basin)

Abstract

In the Schleswig-Holstein area, salty groundwaters are not always spatially related to the presence of shallow salt structures. Furthermore, hydrogeochemical data point to instable salinity profiles and to the occurrences of deep brines close to the surface. Therefore, complex interaction between shallow and deep solute migration must occur.Numerical simulation of fluid flow, mass and heat transport have been carried out in order to understand the role of shallow salt dissolution and young geological features on groundwater flow as well as to investigate the interrelationships between shallow and deep aquifer-systems. For these purposes, a shallow (-500 m) and a deep profile model (-5 km) have been constructed.The results indicate that different flow regimes coexist within the study area. Shallow brine migration is strongly controlled by the geological features of the basin such as faults, Pleistocene channels and sand layers. Furthermore, shallow salt dissolution is the major cause for gravitational convection in the deeper aquifers. This source of salinization from above leads to the formation of instable salinity profiles at 2 km depth. Further interactions between shallow and deep fluid flow exist in the eastern part of the basin where brine upconing is due to both topographydriven flow and thermohaline convection. The simulations also showed that the hydraulic conductivity of the stratigraphic units influences the brine regime on a regional scale. Gravitational convection is likely to occur in permeable units located near shallow salt structures, while thermohaline convection persists within thick permeable units in which salt dissolution is not the dominant process.The presented study provides new insights into fluid flow processes at basin scale. The described flows could develop in any geothermal basin hosting salt diapirs which pierce shallow aquifer systems.

Quaternary channels within the Northeast German Basin and their relevance on double diffusive convective transport processes: Constraints from 3‐D thermohaline numerical simulations

“…[12] As a matter of fact, most numerical investigations that have been devoted to DDC transport phenomena and their relevance for different basin systems worldwide are essentially twodimensional [Sarkar et al, 1995;Ma et al, 2006;Magri et al, 2009aMagri et al, , 2009b. Despite the considerable amount of insights gained from these studies little is known about the full three-dimensional dynamics of DDC processes.…”

Achievements and Challenges in Sedimentary Basin Dynamics: A Review

“…Promising results have already been obtained in the simulation of thermo-haline circulations in the Northeast German Basin, thus accounting for the advection of saline water derived from Permian salt layers up to the surface ( Fig. 47; Magri et al, 2005aMagri et al, , b, 2007Magri et al, 2008). Magri et al, 2005aMagri et al, , b, 2007Magri et al, , 2008 0 25 km …”

The effects of ascent recharge on deep exploitable aquifers on the North European Plain (a case study of the Rogoźno salt anticline, Poland)

“…The groundwaters of the Me sozoic aqui fer are char ac ter ized by high min er ali sa tion and of ten an oma lously high piezometric pres sures, in clud ing ar te sian (Dowgia³³o, 1965;Bojarski, 1996). Zones par tic u larly pre disposed to trans port of as cent brines to ex ploit able aqui fers are tec tonic dis con ti nu ities, of ten ge net i cally re lated to nu mer ous salt struc tures (Ev ans et al, 1991;Magri et al, 2009). The results of re search car ried out by Grube (2000) in north ern Germany point to sig nif i cance of as cent as a threat to fresh groundwa ter re sources.…”

“…De tailed re search has al lowed doc u ment ing zones of shal low and even subsurface as cent in flu ence in the ar eas of salt pil lows (Kucharski and Twarogowski, 1995;Kaczor, 2006), sea coasts (Dowgia³³o, 1965;Burzyñski et al, 1999;Krawiec, 2013) and salt domes (Kloppmann et al, 2001;Górski and Rasa³a, 2008). Iden ti fi ca tion of as cent re charge zones is mainly based on ad vanced geo phys i cal, mod el ling and iso to pic meth -ods (e.g., Burzyñski et al, 2004;Langevin and Guo, 2006;Magri et al, 2009;Zarroca et al, 2011;Gurwin and Krawiec, 2012;Krawiec, 2013). Most works on the topic con cern chiefly iden ti fi ca tion of as cent re charge sys tems, ground wa ter or i gin, and/or dis tri bu tion of el e vated chlo ride con cen tra tions as the most re li able in di ca tor of as cent re charge of ex ploit able aquifers.…”