Assessment of Groundwater for Agricultural Uses in Urmia Plain with Combined Method of Pollution Vulnerability and Potential Models and Groundwater Quality Index

In this study, the groundwater resources of Urmia Plain were evaluated for agricultural uses using a combined method that includes vulnerability, potential, and groundwater quality models. The vulnerability was evaluated by the DRASTIC method and the final map was classified into five classes with very high to very low vulnerability. The layers of NDVI, digital elevation model, drainage density, precipitation, and well density were considered as inputs of the potential model, and Analytical Hierarchy Process (AHP) was used to determine the weight of each layer. The potential map was also classified into five classes with very high to very low potential. The groundwater quality map was produced with three input layers including electrical conductivity (EC), sodium absorption ratio (SAR), and residual sodium carbonate (RSC) and weighting method. The combined map was produced by the maximum likelihood classification (MLC) method with five classes. The first and second zones with 40.31% of the area are suitable for agricultural uses, which include the northern, northwestern, and central semi-northern regions. The third zone with 22.90% of the area is in moderate condition and includes the central areas of the northern half and the southern half. The fourth and fifth zones with 36.79% of the area are in unsuitable conditions for agricultural use.