Abstract: The Bohai Bay is encircled by the Bohai Sea economic zone and faces high pressure of environmental protection due to its high pollution load. Water exchange capacity is a key factor of environmental capacity, and in the bay it is dominated by tides and winds. This study develops a water age model using an Eulerian approach, and simulates the role of winds in water exchange in this bay, focusing on comparison of the water age and its temporal and spatial distribution characteristics between two cases ? under the combined effects of tides and winds, and under the effect of tides only. The results show wind action is a crucial factor of water exchange that greatly accelerates the exchange between the bay and the Yellow Sea. Seasonal variations in water age reveal that the exchange between the bay and the central Bohai Sea is strong in winter and weak in summer.

Key words: Bohai Bay, wind stress, water exchange, water age, seasonal variation