Influence of brittle deformation on waterflow and retention observed in a cave (Hochschwab, Eastern Alps)

Abstract

The complex geological processes driving flow and retention of water in the upper vadose zone of Alpine karst aquifers are yet to be understood to a sufficient level. To gather a deeper understanding into these systems, a structural geology approach was combined with electrical resistivity tomography to find a link between brittle deformation structures and recharged water into karst systems. The investigated Hirschgruben cave is located in the central Hochschwab massif at an elevation of 1896 m a.s.l. and shows horizontal character in its studied passages. Electrical resistivity tomography data and discharge of cave drip water was gathered during snowmelt and summer precipitation events. Examined areas were grouped into different classes of fracture spacing, ranging from massive rock to finely fractured rock in the vicinity of brittle faults. These records fit existing models of deformation stages in the Eastern Alps. Inhomogeneities in water infiltration along existing fracture zones were observed to some extent and appear to depend on both, the fracture density in the host rock as well as rate of water infiltration. These results help to understand the behaviour of water in the upper vadose zone and subsequently provide valuable information for the supply of karst water as a source of drinking water.