Numerical Modeling of the Freshwater Lens in Small Islands (Case Study of Kish Island)

The groundwater system in many small islands consists of a freshwater lens surrounded by seawater.A transition zone exists between the freshwater and the seawater in which relative salinity graduallychanges from zero to 100 percent. Saltwater intrusion is the most important hazard to groundwaterquality in small islands. Kish Island is one of the few islands in the Persian Gulf with extractable freshgroundwater resources. This paper presents details of a comprehensive study conducted to modelseawater intrusion in Kish Island. Three dimensional numerical simulations were carried out usingSUTRA a density dependent flow and transport numerical model. Model calibration was performed byInverse modeling. For this purpose the PEST inverse code was combined with SUTRA. Finally modelsensitivity was evaluated for aquifer recharge and permeability. This study shows that SUTRA can beregarded as a valuable tool in saltwater intrusion modeling. This is mainly due to the model`s ability tosimultaneously solve flow and solute transport equations, as well as other key features of the modelsuch as its ability to simulate the transition zone and the unsaturated layer above the main aquifer andto model the groundwater system in three dimensions.