ABSTRACT
Nakdong Estuary Dam in South Korea was constructed in 1987 to secure fresh water of the Nakdong River reach upstream. Currently, gates of the estuary dam are opened only when the upstream water level is higher than the coastal water level to prevent seawater intrusion to the upstream. Now, the management policy has changed such that the gates of the estuary dam will be opened continually to improve the water quality and restore the estuarine ecosystem by circulating the coastal and fresh waters. This study simulated the seawater intrusions for various partial gate-opening scenarios with a numerical model utilizing the finite volume method and unstructured grids. The simulation results in that the salt intrusion developed up to 27 km from the estuary dam under the worst condition in the scenarios. Since major withdrawals are located at 15 km from the dam, salt intrusion is not allowed to reach that place. Therefore, the present simulations suggest the operational strategies to prevent salinity from being taken in and simultaneously circulate freshwater and seawater through the dam. Along with the operational strategies, we showed how salt intrusion responds to the tidal and fresh water conditions. Finally, at given conditions, the optimal gate operations are proposed.
