Evaluation of intrinsic vulnerability of an Upper Jurassic karst-fissured aquifer in the Jura Krakowska (southern Poland) to anthropogenic pollution using the DRASTIC method

Abstract

This paper demonstrates the evaluation of intrinsic vulnerability of karst-fissured waters in an Upper Jurassic aquifer by applying modified DRASTIC method. The area investigated is the Jura Krakowska (South Poland) -- an area of upland merokarst (or relict karst), where the Upper Jurassic aquifer is mainly unconfined. The method applied is a combination of a simulation model of the groundwater aquifer (factors: net recharge, hydraulic conductivity, groundwater flow velocity in the aquifer) and a geographical information system -- GIS model (depth of groundwater table, lithology of vadose zone, thickness of Upper Jurassic aquifer), and additionally a soil factor was taken into account. In the area of the Jura Krakowska, 5 classes of intrinsic vulnerability to pollution were distinguished according to the values of vulnerability factors. These classes range from extremely high to low vulnerability (IP 200-50). Based on the synthetic map of vulnerability it emerges that high vulnerability indices cover 54% of the area studied while medium and low vulnerability indices cover 46% of this area. The modified DRASTIC method presented seems to be a useful tool to evaluate the intrinsic vulnerability of karst-fissured aquifers of "Torcal" type with a scattered system of recharge and discharge, and a thick vadose zone of variable permeability. This is consistent with the method developed with European programme COST ACTION 620. All rating methods recommended for karst have limitations, therefore the method applied is constantly updated. Many of them are particularly useful for areas of bare karst, mountain systems of "Aliou" type and in areas of complete karst development (holokarst).