GIS TECHNIQUES FOR MAPPING GROUNDWATER CONTAMINATION RISK

Daniela Ducci (Istituto di Geologia Applicata, Facolta' di Ingegneria. Universita' di Napoli, Piazzale Tecchio 80 80125 Napoli, Italy)

The groundwater contamination risk map at a medium scale (1:50.000) of a sample alluvial area has been produced. The parametric method for pollution risk assess ment proposed by Civita (1995) has been adopted. According to this approach to e valuate the ground-water pollution risk, the hazard, which is function of time, is substituted by the "danger", function of the spatial distribution of the cont amination sources. The damage is quantified as the product of the impact subject s vulnerability by the value. The risk map is obtained crossing the thematic map s. The geographical information system ILWIS has been used to construct and to o verlay the thematic maps, with pixel size of 30 x 30 m. For instance the process ing to construct the ground-water quality map were carried out in a GIS environm ent, applying the method described by the author in a previous paper. The procedures used to evaluate the risk by Civita were partially modified consi dering the whole aquifer as the impact subject and only the catchments as the va lue, according to the hydrogeological setting and the adopted scale. The use of a GIS permitted, by the developement of analytical procedures, to opt imize the groundwater contamination risk assessment method, through: - high spat ial resolution; - numeric checking of calculated parameters; - easy matrix opera tions. The GIS technique proposed needs to be refined by testing and improving the meth od in various hydrogeological environments.