However, the correlation coefficient decreased to R = 0.37 for the 2012 nitrate samples. Such decrease in R is due to the in creased fertilizer use in the Kerman plain because of the intense agricultural activity in the region. One of the best methods for comparing the results of groundwater vulnerability is Pearson’s correlation coefficient. The results of the comparison between ground water vulnerability maps and nitrate concentration derived from Pear-son’s correlation coefficient shows that the model is suitable for the study area. The correlations between these results reveal that among the five applied methods and the nitrate concentration, the AHP–AHP method was the most suitable model for the Kerman plain, with a considerably high correlation of 0.83. The correlation coefficient of AHP–AHP for the Kerman plain shows that the most appropriate result for groundwater vulnerability can be obtained based on experts’ choice corresponding to the condition of the study area.