Delineation of a karst aquifer using geological and hydrological data and information on landscape development

Abstract

The boundaries of the Gallusquelle karst aquifer (Malm, SW Germany) were successfully derived using an integrated approach with direct information on the degree of karstification from borehole cores, indirect evidence from groundwater level hydrographs, and from the geological history of the catchment area. Whereas borehole logs provide point information on the degree of karstification, the groundwater hydrograph data reflect the integrated hydraulic characteristics of a much larger aquifer volume. The information on landscape development, such as the positions of the Tertiary coast line (“cliff”) or the topographic elevations of the springs during the Quaternary Alpine glaciation provide valuable quantitative data on the position of potential zones of enhanced karstification. Low regional hydraulic gradients (high hydraulic conductivity zone) were observed in the area most likely subjected to paleo-karstification at the salt/fresh water interface of the Tertiary sea. The rate of change in the water level records reveals details about the vertical change in hydraulic parameters. Further evidence of a change in the hydraulic properties of the aquifer is provided by information on the position of the Quaternary zone of groundwater table fluctuation, where enhanced karstification occurred.