Saltwater intrusion vulnerability assessment using AHP-GALDIT model in Kashan plain aquifer as critical aquifer in a semi-arid region

Owing to population growth and water demand, coastal aquifers all over the world are over–pumped, resulting in serious problems such as saltwater intrusion. So, in these conditions, assessing the groundwater system’s vulnerability and finding areas with saltwater intrusion potential are vital for the better management of aquifers. In this study, AHP-GALDIT was applied to saltwater intrusion vulnerability assessment in the Kashan plain. The AHP model determines the weight of each indicator in the GALDIT model. The most important indicators of the AHP model are distance from shore/high tide, groundwater head, groundwater system hydraulic conductivity, impact of present status of saltwater intrusion, saturated media depth, and groundwater occurrence. The AHP-GALDIT distribution map indicates four different rating areas in the Kashan plain, including: more than 10, 7.5 to 5, 5 to 2.5 and less than 2.5, which denote high, average, low, and very low vulnerability, which correspond to approximately 16.16, 25.51, 21.26, and 36.05% of the entire area, respectively. The results reveal that the northeastern part of this inland coastal aquifer is currently undergoing saltwater intrusion. But, it is not clear whether the source of salinity is saltwater intrusion from the “salt lake”, upcoming processes, or other sources. This study proves that the GIS-based AHP-GALDIT model is suitable to determine vulnerable sites with high accuracy by using the set of indicators affecting the vulnerability assessment.