Kahriz plain aquifer vulnerability assessment using Drastic Model in GIS

Aquifer vulnerability assessment is very important for developing, management, making land use decisions, monitoring of groundwater resources quality and prevent groundwater contamination. In this research, vulnerability of Kahriz plain aquifer was evaluated by DRASTIC model and Geographic Information System (GIS). The model combines seven hydrological factors affecting groundwater contamination. These factors include: depth of groundwater level, aquifer net recharge, aquifer media, soil media, topography, Unsaturated Zone and hydraulic conductivity of the aquifer. Based on overlapping of resultant map vulnerability zoning map of the aquifer was prepared. Two main vulnerable zones including low and moderate vulnerable zone were determined. Area of moderate and low vulnerable zones are about 78 and 22 percent, respectively. Model validation was performed using the dispersion of nitrate concentration in the aquifer. Almost all areas with high nitrate were in the moderate vulnerable range.