Assessing Vulnerability Aquifer of Urmia Nazluchay Plain, Using DRASTIC Model and it's Verification with NITRATE Concentration in GIS Environment

Nazloochay plain is located at north western of Urmia city in Iran. The approximate area of the plain is 508 Km2. It's located on the western coast of Urmia lake and is part of the Urmia basin. This research DRASTIC model was used to evaluate pollution vulnerability of aquifer of the region. DRASTIC model can be considered as the most common overlap index method used in these cases which considers seven hydrogeological parameters affecting ground water pollution including: Depth of ground water(D), net Recharge(R), Aquifer environment(A), Soil type(S), Topography(T), Impact of unsaturated zone(I) and Hydraulic conductivity(C). Combining these parameters of the model using GIS, indicated high pollution potential regions of aquifer and nitrate concentration has been applied to estimate the verification. DRASTIC vulnerability index of model was estimated between 38-153 for this case study, consisting of five ranges of pollution including: negligible; low (%44); little (33%); average (15%) and high (8%). According to designated vulnerability maps, the highest vulnerability potential is in central and southern section of the studying region. Based on nitrate concentration in pollution vulnerability shown in DRASTIC model, all area with high amount of nitrate were located in two categories of high and moderate ranges pollution susceptibility which confirms the model accuracy and preciseness.