Using Fuzzy logic and AHP models to modify GALDIT model in coastal aquifer vulnerability assessment

Groundwater as a source of drinking water is very important in coastal aquifers. Groundwater vulnerability maps can be used to protect the quality of groundwater resources. Therefore, in this study, GALDIT model was applied to assess and determine vulnerable areas to seawater intrusion in Gharesoo-Gorgan Rood coastal aquifer. The GALDIT model is a type of the rating models and needs to be calibrated in each study area. The novelty of this study is to use the Fuzzy Logic model to modify the GALDIT model. In addition, the weights of this model were modified by Analytical Hierarchy Process (AHP). Then, the pearson’s correlation coefficient was used to validate the results. Correlation coefficient between Fuzzy-AHP and GALDIT-AHP models with TDS concentration was 0.63 and 0.51, respectively. As a result, the optimal model for the study area is the Fuzzy-AHP model. The results of the vulnerability map indicate that the northwest and west of aquifer areas are highly vulnerable to the seawater intrusion. The Fuzzy Logic model can be used as an effective way to modify the GALDIT model and ensure its results.