Assessment of Groundwater Vulnerability Using a-GIS Based DRASTIC Model (Case Study: Dehgolan Plain, Kurdistan Province)

In spite of The uncontrolled exploitation of groundwater that has caused a sharp drop in water level, Agricultural, industrial and urban activities enter contaminant to various aquifers. Due to Dehgolan plain importance in water supply of industrial, drinking and agriculture, for the vulnerability assessment DRASTIC model was used. The DRASTIC model uses seven environmental parameters (Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone and hydraulic Conductivity) to characterize the hydrogeological setting and evaluate aquifer vulnerability. These factors were produced as 7 layers in Arc GIS 9.3 software and by Weighting, Rating and combination, final map of Groundwater vulnerability to pollution was provided 5 zones as: without risk of pollution, very low, low, low to moderate and moderate to high and finally DRASTIC Index ranging from 41 to 159 for all the case studies were estimated. Nitrate concentration and EC were used to validate the final map of vulnerability. Overlying these elements, concentration to the DRASTIC final map, illustrated that all point with high concentration stand in the high pollution zones and this result showed the acceptable accuracy of DRASTIC model. From point of area view, 7.79% of plain lies in without risk of pollution class, 40.92% of plain in very low class, 41.61% of plain in low class, 9.66% of plain in low to moderate class and only 0.02% of plain drops in moderate to high class.