Vulnerability Assessment of an Aquifer Using Modified GIS-Based Methods

The primary goal of this research was to compare several computational techniques to identify a groundwater vulnerability index across the Sefid-Dasht aquifer in Iran. A model using the aquifer characteristics (depth, net recharge, soil media, aquifer media, impact of unsaturated zone, and hydraulic conductivity), the DRASTIC model, was applied to calculate vulnerability index of the mentioned aquifer considering two aspects of the conventional and modified procedures. A fuzzy geographic information system-based DRASTIC model was also used. The conventional DRASTIC vulnerability index map indicated that 69.5 and 30.5% of the aquifer had low and moderate vulnerability, respectively. Similar results were obtained from the modified DRASTIC method, which showed that 79.22, 20.46, and 0.31% of the aquifer has low, moderate, and high vulnerability, respectively. Because of similarity in the results and the simplicity of the modified DRASTIC, the application of the former method is recommended. In the fuzzy-DRASTIC method, final maps indicated no major difference between this method and the conventional DRASTIC model.