Characterization of groundwater vulnerability to fulfill requirements of the water framework directive of the European Union

Abstract

Aquifer vulnerability assessment is an important basis in order to fulfill demands of the water framework directive of the European Union. For the determination of the groundwater vulnerability different methods can be used. In this paper, the intrinsic vulnerability of groundwater resources is defined as the worst case of a pollution input in the unsaturated zone without interaction or decay of the contamination substance on its way to groundwater table. It can be assessed by the transit time of the percolating water from surface to the groundwater table. To asses the groundwater vulnerability according to this definition, a method based on a simple analytic model which determines the retention time of the percolating water in the unsaturated zone is presented. The computation of the retention time is based on lithological characteristics of the vadose zone and on the groundwater recharge rate. The method has the advantage that the necessary input data can to be derived from available maps and can be handled by a GIS.