Using TODIM decision method to control saltwater intrusion by numerical simulation approach (study area: Nowshahr-Nur aquifer)

Over-pumping of aquifers and lack of planning for the water resources, and allocation system in coastal aquifers, in addition to minor problems, disturb the ecological balance. This type of exploitation reduces the groundwater level and the hydraulic gradient in the coastal strip and, due to the higher density of saline water, includes the invasion of saline water and salinization of groundwater resources. Due to population growth, migration, drought, and over-pumping in the southern part of the Caspian Sea, this issue has disturbed the balance of groundwater resources, and most of the coastline has been associated with increasing solute concentrations. Accordingly, in this study, using the SEAWAT code, the intrusion of saltwater in the Nowshahr-Nur aquifer has been simulated, and the results analyzed, which showed that in the current situation, saline water intrusion spreads a wide width of 862 m from the aquifer. To control the current situation of saline water invasion in the coastal strip, seven treatment strategies were simulated and the TODIM decision-making method was used to prioritize. For this purpose, four criteria of economic, social, environmental, and groundwater level improvement were selected for decision-making and weighed by hierarchical analysis. The weighting results showed that the criterion for improving the groundwater level with a weight of 0.311 is the most important. Based on the weighting of the criteria, the strategies were prioritized and the results showed that a 20% reduction in aquifer abstraction by combining the construction of an underground barrier was selected as a solution to control the invasion of short water. The results of this solution showed that 317 m of saline water backflow will arise in the Nowshahr-Nur aquifer.