A GIS-based study to evaluate effect of water table changes on DRASTIC model for vulnerability assessment of groundwater: A case study of Kermanshah, Iran

Groundwater is considered as an important source of water supply in our world. Its contamination is of particular concern as it is a vital source of water for irrigation, drinking and industrial activities. To control and manage groundwater contamination DRASTIC model is a popular approach. This study applied an integrated DRASTIC model using Geographic Information Science (GIS) tool to evaluate groundwater vulnerability of Kermanshah plain, Iran considering water table fluctuation. High fluctuation of water table depth due to wet and dry season in arid and semi-arid areas is notable. The study area is affected by this problem, thus this research investigated the effect of minimum depth water during one year respect to average water depth which is common for this model. Results represent considerable differences for two types of produced maps; map using mean of water table for 5 year and map of minimum water table of one year. Vulnerability maps of mean data classified 40% of the study area as no risk of pollution while this is around 25% for vulnerability maps of minimum depth. In spite, minimum depth vulnerability maps classified around 12% of the study area as moderate risk which is 6% greater than mean depth vulnerability maps. In case of accuracy, results show more correlation between Nitrate data (NO3 −) and vulnerability maps of minimum water table