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 Republic is known to have suffered from heavy acid atmospheric deposition which has led to mass extinction of the forest cover in apical parts of the mountains and to degradation of groundwater quality. A methodology for construction of groundwater vulnerability maps, using a Geographical Information System (GIS), has been developed as a tool for protecting the groundwater resources. The maps were constructed by using four subsidiary layers, each of which reflects 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) lithology of the aquifer. A step-wise analysis and application of the data in each of the layers was accomplished to compare changes in the quality of groundwaters, and to obtain the best weighting factors for the individual parameters. Changes in alkalinity of the groundwater during the last 30 years were used as a test criterion. The vulnerability map should be a valuable tool to identify and outline areas most vulnerable to acidification and also areas considered for reforestation.