Vulnerability of groundwater to acid deposition, Jizerske Mountains, northern Czech Republic: construction and reliability of a GIS-based vulnerability map

The area of the Jizerske Mountains in the northern part of the Czech Republ ic is known to have suffered from heavy acid atmospheric deposition which h as led to mass extinction of the forest cover in apical parts of the mounta ins and to degradation of groundwater quality. A methodology for constructi on of groundwater vulnerability maps, using a Geographical Information Syst em (GIS), has been developed as a tool for protecting the groundwater resou rces. The maps were constructed by using four subsidiary layers, each of which re flects a particular parameter that governs acidification. The factors that determine vulnerability are: (1) elevation above sea level, (2) morphology of the terrain, (3) areal extent and type of vegetation cover, and (4) lith ology of the aquifer. A step-wise analysis and application of the data in e ach of the layers was accomplished to compare changes in the quality of gro undwaters, and to obtain the best weighting factors for the individual para meters. Changes in alkalinity of the groundwater during the last 30 years w ere used as a test criterion. The vulnerability map should be a valuable tool to identify and outline are as most vulnerable to acidification and also areas considered for reforesta tion.