Abstract
Abstract. Due to their heterogeneous nature, karst aquifers pose a major challenge for hydrogeological investigations. Important procedures like the delineation of catchment areas for springs are hindered by the unknown locations and hydraulic properties of highly conductive karstic zones. In this work numerical modeling was employed as a tool in delineating catchment areas of several springs within a karst area in southwestern Germany. For this purpose, different distributive modeling approaches were implemented in the finite element simulation software Comsol Multiphysics®. The investigation focuses on the question to which degree the effect of karstification has to be taken into account for accurately simulating the hydraulic head distribution and the observed spring discharges. The results reveal that the representation of heterogeneities has a large influence on the delineation of the catchment areas. Not only the location of highly conductive elements but also their geometries play a major role for the resulting hydraulic head distribution and thus for catchment area delineation. The size distribution of the karst conduits derived from the numerical models agrees with knowledge from karst genesis. It was thus shown that numerical modeling is a useful tool for catchment delineation in karst aquifers based on results from different field observations.
Highlights
Karst aquifers are strongly heterogeneous systems due to a local development of large-scale discontinuities such as conduit systems
The results reveal that the representation of heterogeneities has a large influence on the delineation of the catchment areas
The results show that distributive numerical simulation is a useful tool for approaching the complex subject of subsurface catchment delineation in karst aquifers as long as effects of karstification are sufficiently taken into account
Summary
Karst aquifers are strongly heterogeneous systems due to a local development of large-scale discontinuities such as conduit systems. This heterogeneity causes a large anisotropy in the hydraulic parameter field. A characteristic attribute of many karst aquifers is their high discharge focused to large springs. This makes them especially interesting as drinking water resources. The delineation of catchment areas of karst springs is still a challenge because of the usually unknown location of large-scale heterogeneities, such as karst conduits, within the aquifer. Catchment areas may change under different hydrological conditions further complicating the issue
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