Numerical Analysis on Saltwater Intrusion and Dispersion is an Unsaturated-Saturated Coastal Aquifer

plied to the numerical computations on saltwater intrusion , dispersion and groundwater flow movement in coastal aquifers. In the present model, unsaturated zone is taken into consideration and this makes it easy to determine the position of free surface. It is shown that the difference between the theoretical solutions of fresh-salt water interface and the salt concentration distribution by numerical method mainly depends on the upward velocity component in the mixing zone. In case of the unsteady flow due to the excavation of the underground cavern , it is shown that the free surface above the cavern is withdrawn and the saltwater begins to move into the cavern due to the flow toward it. It is also shown that the discharge into cavern rapidly decreases immediately after excavating the cavern and then gradually approaches to the constant value. It is concluded that the