Damming of rivers has impact on these natural waters and their environment. For example, integrity of tidal rivers depends on the balance between freshwater and oceanic seawater and reducing the freshwater input and disturbs this balance. Prolonged low-flow condition allows salinity intrusion in the upstream which deteriorates both the surface water quality and even the ground water quality. This study deals with the salt intrusion prediction in the Arvand estuary in the south west of Iran. The hydrological conditions in the Arvand are continuously changing. Asteady reduction of the discharge of the rivers from which the Arvand River receives its water is caused by a consecutive development of irrigation and industrial schemes along the river courses,which demands construction of dams.A laterally averaged, two-dimensional hydrodynamics-water quality model called CE-QUAL-W2, was used for simulation of flow and salinity intrusion in this river. Recorded tidal levels of gauging stations in Abadan and Ghosbeh were used for calibrating the hydrodynamic module. The best fit of the recorded and computed water levels curves at Ghosbeh was obtained with a Manning friction factor of 0.02. After calibration of the model the maximum length of salt wedge intrusion was predicted both by numerical simulation and three empirical equations. It was found that most of the existing predictive models are limited to special conditions and are not valid for Arvand River. However, the method which was described by Savenije (1993) performs the best.