Karst areas are critical environments for groundwater, representing the source of drinking water for
ca. 50% of the population in Austrian and about 25% of the population in Europe. Karst refers to
complex, predominantly underground drainage systems and special land features that are created by
the dissolution of rock (mostly limestone). In terms of groundwater flow inside the mountains, it is
possible to distinguish the partially water-filled vadose zone and the completely water-filled phreatic
zone below the water table. In the vadose zone, karst caves and shafts created by dissolution allow
water to drain away quickly. This in turn makes the groundwater in the phreatic zone, which feeds
the drinking water sources, vulnerable to contamination. Therefore, groundwater modelling and
management requires a detailed understanding of the waterways as well as the storage of the water
in the rocks and caves. Karst caves allow direct access and thus measurements in the vadose zone.
In this study, we focus on the Hochschwab karst massif where more than 1000 mainly shaft-like
caves are known. The area is of particular importance as it is the water supply of the cities of Vienna
and Graz and. In recent decades, numerous studies have been carried out in this area dealing with
rock formation and structures, water conditions as well as caves and karst features, which form a
good basis for this project. However, none of those studies have addressed geophysical monitoring.
To study water flow and storage in the vadose zone, as well as groundwater recharge and storage in
the karst system, we will use different geophysical methods, which permit to monitor changes in
groundwater properties in a non-invasive manner and the possibility to investigate areas not
accessible with common hydrological sensors. Geophysical results are supported through measuring
stations located at cave streams that can provide direct information, for instance how quickly they
react to rain events.
The application of different methods should lead to a joint analysis of the data as well as to an
interdisciplinary evaluation of the results. The aim of the project is to find a connection between the
fracture surfaces in the rock and the surface and underground karst forms with the flow or storage
properties of the water.
For the implementation, a close interdisciplinary cooperation between the Karst and Caves Group at
the Natural History Museum Vienna and the Department of Geodesy and Geoinformation at the TU
Wien, in particular the Research unit of Geophysics. The outcome of the project will be discussed
with other groups dealing with groundwater management and modelling as well.