Hydrogeologie im Tauernfenster - Fallbeispiel Rauristal, Salzburg

The aim of this case study in a small-scale catchment at altitudes between 1.500 and 2.500 m asl in the Rauristal in Salzburg was to exemplify the hydrogeological character of some typical lithologies and structures along the northern margin of the Tauern Window. The study area is built up by metamorphic schist and gneiss of penninic and subpenninic nappes and various quaternary deposits. Approximately 10 km² were mapped with regard to geology and hydrogeological aspects such as springs, surface runoff, and sinkholes. Discharge measurements were performed three times and three boreholes were drilled to investigate the hydrogeological situation of a large landslide deposit.
Five different flow systems were identified: (1) layer-based springs at the boundary between gneiss and schist result from different hydraulic conductivities of involved units. While gneiss is a comparably high permeable fractured aquifer, schists act as aquitard in this setting. (2) Barrier springs are related to Moraine deposits. (3) Spring lines within schists follow the main regional fracture direction. (4) Numerous small springs refer to near surface flow systems within debris layers. (5) The large landslide deposit represents an aquifer with good hydraulic conductivity. Due to weathering layers it is partially impermeable for infiltration which leads to numerous small ponds in the upper part of the landslide deposit.