Abstract: Transport time scale of estuary and nearshore areas is an important agent connecting the marine physical processes and the ecological processes which reflace the exchange of water and materials in it. It is of vital importance to investigate the transport time scale in the Beilun River estuary to control marine environmental pollutions efficiently and to promote the reasonable shoreline development. A high-resolution 2-Dimensional numerical model is established and applied in the Beilun River estuary to calculate the residence times and their reactions to river discharge, tidal range and topography. The results show that the residence times in the outer areas adjacent to the Beilun River estuary are less than 20h. Near the river mouth, the residence times exhibit great variations with a range between 30h to 200h under different conditions of river discharges and/or tidal ranges. In the Zhenzhu Gulf, the residence times show great spatial variations as tidal range changes. In the inner subzone Z1, the residence time is 413.7h, while in the outer subzone Z4, the residence time is only 3.5h. The residence time decreases gradually from the river mouth to outer areas and from the channel to the shoal. In the Zhenzhu Gulf, the residence time is much longer than those in the marginal shallow zones. The residence time can be fitted satisfactorily with the river discharge by quadratic polynomials. the influences of river discharge to residence time become weaker from river mouth to the outer zones and from channel to shallow areas. The residence time increases as the tidal range decreases and the changes are larger near river mouth than that in the outer seas. In the Beilun River estuary, the dominate influence on residence time is due to tidal flushing rather than river dischange.

Key words: Beilun River estuary, Zhenzhu Gulf, residence time, numerical simulation