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Abstract

Groundwater is the world's most abundant and exploited resource, and in many places, it is the population's only source of drinking water. Research is constantly facing new challenges regarding the exploitation of georesources in deep groundwater systems (e.g. CO2 storage, geothermal energy, unconventional gas reserves or energy storage) and the resulting effects on drinking water as a protected resource in shallow groundwater systems. The hydraulic connection between the two groundwater zones (shallow and deep), as well as existing migration pathways (fault zones and discontinuities in aquitards) have not yet been sufficiently or at all taken into account or studied. In many areas, salt and fresh water are separated by large-scale regionally occurring aquitards (formations with very low hydraulic conductivity), and the occurrence of fresh water is therefore often restricted to a thickness of a few 100 metres. The presence of such aquitards divides the area into a shallow groundwater system (fresh water) and a deep groundwater system (saltwater). The saltwater at greater depths does not participate in the surface-near water cycle, or only does so to a limited extent. However, because the generally regionally occurring aquitards have discontinuities and fault zones, along which the fresh water can reach the deep groundwater system and saltwater can migrate into the shallow groundwater systems, there is a hydraulic connection between the deep and shallow groundwater zones. The system analysis of groundwater zones is performed with numerical simulation programs. The focal point in this area is the simulation of thermal, hydraulic, mechanical and chemical coupled processes. Existing field data on groundwater hydraulics, hydrochemistry and geomechanics represent an important basis for the numerical simulation. Various numerical applications related to interactions of deep and shallow groundwater systems are presented.