Large areas of Austria are built up by crystalline hard rocks like the Central Alps or the Bohemian Massive developing fractured aquifers. These aquifers provide a lot of drinking water supplies and they are coupled with hydrogeological requirements in respect of infrastructural constructions sites like e.g. tunnels.
Water flow in fractured hard rocks is predominantly influenced by faults causing fault zones and/or a fracture network consisting mostly of several fracture sets. The hydraulic properties of fractured aquifers can be described by hydraulic tests and geophysical borehole logging or by detailed analysis of the fracture network including the spatial and the hydraulic relevant properties at exposures (dip angle, dip direction, aperture, termination, ..).
Karst aquifers develop where the dissolution of soluble rocks such as limestone and gypsum causes a widening of fractures, thus creating highly permeable solution conduits and caves. The karst conduit system, however, occupies only a small portion of the total aquifer porosity. The vast majority of storage is provided by not substantially widened fissures (i.e., narrow fractures) and/or by the porous rock matrix. Karst aquifers represent important water resources, supplying drinking water for an estimated quarter of the world's population. In Austria karst aquifers provide approximately 50% of the drinking water. Effective protection and sustainable use of karst waters require knowledge about aquifer properties relevant to flow and solute transport.