Modeling of karst groundwater vulnerability

Prof. Dr. P. Huggenberger, Dr. C. Butscher

Karst groundwater is a major resource for numerous regions in Europe. Also in Switzerland, karst groundwater is indispensable for the drinking water supply. The ecological importance of karst groundwater as a prerequisite of sensitive habitats, like natural springs and spring brooks, is also increasingly recognized. However, karst aquifers are particularly vulnerable to contamination due to the often thin soil cover, concentrated infiltration and short groundwater residence times. Therefore, our research is concerned with an improvement of the knowledge about karst specific hydrogeological processes and of methods for the evaluation of groundwater vulnerability.

The applied methodology includes the numerical simulation of flow processes, based on rainfall-discharge models. The simulations serve to quantify karst groundwater vulnerability and its temporal variation. New criteria were established for the evaluation of the vulnerability: the vulnerability index VI, which specifies the impact of short-lived contaminants on spring water quality, and the vulnerability concentration CV, which represents the sensitivity of karst springs to a potential pollution with persistent contaminants. The time variant modeling of vulnerability can also be applied to future recharge scenarios and, by that, allows assessing the effects of predicted climate change on karst groundwater resources.

Apart from the evaluation of temporal aspects of vulnerability, the approach additionally allows comparing different springs quantitatively with regard to their contamination risk. The results from the numerical modeling can be combined with results from vulnerability mapping in the catchment areas. A combined mapping and modeling approach facilitates an enhanced protection of karst groundwater resources by providing a conceptual framework for an integrative vulnerability assessment. This can be of great practical relevance, contributing to an improved drinking water management and sustainable regional planning of water resources.

Conceptual model of karst groundwater flow and storage as the basis for numerical rainfall-discharge models.

The modeled time series of the vulnerability index VI can be used to analyze the time dependence of vulnerability.