Evaluation of Salmas Plain Aquifer Vulnerability to Pollution Using DRASTIC Model and GIS

In this research vulnerability of Salmas-plain aquifer to pollution was evaluated using the DRASTIC model and Geographic Information System. In DRASTIC model seven effective hydrogeological parameters on groundwater contamination; namely depth of water table, aquifer net recharge, aquifer media, soil texture, topography, impact of vadose zone and hydraulic conductivity were combined. Vulnerability zoning map showed three main zones of low groundwater vulnerability zone (risk index: 64-100), moderate groundwater vulnerability zone (risk index: 100-140) and high groundwater vulnerability zone (risk index: 140-183). Areas with low, moderate and high risk zones comprise 13.55%, 72.09% and 14.36% of the studied area, respectively. Two sensitivity analyses tests including the map removal and the single-parameter sensitivity analyses were carried out. Both of sensitivity analyses tests showed that the depth of water table and vadose zone parameters had the most significant impacts on the vulnerability indexes at the studied region.