Groundwater Vulnerability Assessment Using GIS-Based DRASTIC Model in the Bazargan and Poldasht Plains

Bazargan and Poldasht plains are located in the north of West Azarbaijan, northwest of Iran. In this area, groundwater supplies main water demands. Aim of this research is assessment of aquifer vulnerability for contamination potential on the basis of hydrogeological conditions of the study area. For this purpose the combined use of the DRASTIC and geographical information system (GIS) demonstrated as an effective method for groundwater pollution risk assessment. The DRASTIC model uses seven environmental parameters (Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity). ArcView software was used to create 7 data layers and finally a groundwater vulnerability map by overlaying the available hydrogeological data. DRASTIC index value was evaluated 71 to 175 for study area. The final DRASTIC model was tested using fluoride concentration data from the aquifer. High fluoride concentrations coincide with the high pollution risk area. This can confirm the precision of the model. Around 3% of the study area was classified as being at low risk, 37% as moderate risk while the remainder was classified as high risk that covered large parts of the east, west and central portion of the area. In view of the importance of the groundwater resources in the study area that used for different purposes, preservation of this area is necessary for prevention of pollution and management of water resources.