GIS techniques for mapping groundwater contamination risk

The groundwater contamination risk map of a sample alluvial area was produced by using the Ilwis Geographical Information System (GIS) to construct and to overlay thematic maps. The risk map has been derived from the vulnerability map, the hazard map, where the potential contaminating sources were identified, and the socio-economic value of the groundwater resource, represented by the wells. The groundwater quality map allowed the reliability of hazard and risk maps to be tested. The final map shows interesting results and stresses the need for the GIS to test and improve on the groundwater contamination risk assessment methods.