Flow pattern and transport behaviour of granitic rock intersected by a highly permeable fault zone

Intensive hydraulic testing and tracer experiments were carried out both on a local and a catchment scale at the Lindau fractured rock test site (Southern Black Forest, Germany). The low permeable granitic rock is intersected by a nearly vertical ore dyke, striking north-south, which drains the surrounding rock due to its high permeability. In the on-going investigations, hydraulic and tracer tests are used as a tool to characterize the flow and transport pattern of the catchment in a quantitative manner. Hydraulic testing on a catchment scale was achieved by opening the boreholes in the Lindau observation tunnel below the water table. Tracer experiments were performed in a small section of the ore dyke as forced-gradient tests under controlled geometric conditions. For the evaluation, analytical solutions of the transport equations were applied. The results show that there is a strong deviation in transport parameters depending on which evaluation method is used. For practical applications a pre-assessment of the flow conditions is necessary to avoid misinterpretation by use of inappropriate modelling concepts.