Assessment of the intrinsic vulnerability of aquifer to pollution in Miandoab Plain based on the AVI, GODS, DRASTIC and modified DRASTIC models

Miandoab Plain is part of the Urmia Lake basin, which has significantly reduced the quantity and quality of its water resources in recent years. Groundwater vulnerability assessments provide a useful method for analyzing the sensitivity of aquifer to the contaminant. The purpose of this study was determining the vulnerability of the aquifer using AVI, GODS, DRASTIC and modified DRASTIC models so that the vulnerability potential to pollution can be determined more exactly. In this study, the data and information provided by the Regional Water Company of East Azarbaijan were used to provide layers needed for the preparation of each vulnerability model in the ArcGIS software. The new rates of modified DRASTIC model calculated using a correlation between each parameter and the nitrate concentration obtained from the analysis of 16 water samples taken in July 2016. The final mapping of the vulnerability maps was also verified by nitrate values. Also, validation of the final vulnerability maps was done with nitrate values. The coefficients of determined values between the nitrate concentration and vulnerability models of AVI, GODS, DRASTIC and modified DRASTIC were estimated to be 0.004, 0.13, 0.18, and 0.33, respectively. The results showed that after calibrating the model with the nitrate data, it is the best model for assessing the vulnerability of Aquifer. Based on this, it was observed that the most vulnerable groundwater pollution is in the northeast and parts of the west of the plain and the least vulnerable in the southern and southeastern parts of the plain.