Saline water intrusions at Modaomen waterway were numerically simulated by using MIKE3 based on measured water levels and salinities in November 2006 and January 2007. Calibrated and validated model showed good fitness for both water level and salinity in case of prediction and observation with good detection indexes. The results indicated that salinity stratification

influenced by topography

diversion ratio and other factors such as tidal fluctuation change

resulted in water density difference and then produced extraordinary change in salinity vertical circulation. The change of salt flux is relative to the tidal flux

suggesting that tide is the carrier of brine.