Evaluation of Intrinsic Vulnerability of Urmia Plain Groundwater Pollution Using Original DRASTIC and Drastic Modified Models

The Assessment of groundwater vulnerability to pollution for groundwater protects, which is affected by high fertilizer use, is a proper tool. Groundwater of Urmia Plain due to various factories and agricultural activities, have potential for contamination. In this study, the modified version of the DRASTIC model and the original DRASTIC model, which is a global model, has investigated the inherent vulnerability potential of Urmia groundwater contamination. The correction of this model based on the revising of the ratings and weights of various factors was carried out using simple statistical methods and in the GIS environment, taking into account the correlation with the concentration of groundwater nitrate. The results showed that aquifer environment (A) did not significant correlation with nitrate concentration and was eliminated from the initial equation. The highest and lowest significant correlation was found between soil factors (s) and depth to groundwater (D), respectively, and weighed 5 and 2.7, respectively. The correction of ratings and weights led to improved zoning map, with the correlation of the DRASTIC index with nitrate concentration versus the original DRASTIC, increased by 11%. Based on the modified index of the Urmia Plain, 4.3, 30.8 and 64.9 percent were low, very low and without risk of pollution, respectively.