A hydrogeological-based multi-criteria method for assessing the vulnerability of coastal aquifers to saltwater intrusion

The interaction between salt and fresh water is an important issue in coastal aquifer management and there are numerous methods used to assess the vulnerability of coastal aquifer systems to saltwater intrusion. The aim of the present study was to present a hydrogeological-based method that could be applied to all coastal aquifer systems to assess their vulnerability to saltwater intrusion. To achieve this goal, five criteria, namely GWQI_SI (I), which shows the magnitude of saltwater Intrusion, groundwater level (L), existing Distance between the aquifer and the shore (D), recharge (R) and the saturated thickness of the aquifer (T) were used to develop a novel multi-criteria decision index, ILDRT. The digital integration of the various weights and rates assigned to the five criteria were carried out based on literature, expert knowledge, and the overlay indexing methods and standards. The proposed approach was evaluated to assess the vulnerability of Iran's Malekan coastal aquifer to saltwater intrusion from Lake Urmia. Results showed that the vulnerability index was most significantly influenced by R based on sensitivity analysis using the map removal method accompanied by single parameter method. Based on the ILDRT results, about 22, 49 and 29% of the total area of the Malekan aquifer was in zones of very low, low and moderate vulnerability to saltwater intrusion, respectively.