Abstract: With the combined effects of the river discharge, tide and wind stress, the spatial/temporal variations as well as the dynamical mechanism of the tidal level and tidal range in the North Branch of the Changjiang Estuary were numerically simulated and quantitatively analyzed in this paper. The monthly mean tidal level in the North Branch is increased gradually from January to July and decreased gradually from October to December. It mainly depends on the residual water level, which is determined by the amount of the river discharge. The tidal range experiences a seasonal variation, with two maximum and two minimum values in a year. These two maximum values appear in March (the second lunar month) and September (the eighth lunar month), and the two minimum ones appear in June (the fifth lunar month) and December (the eleventh lunar month), respectively. The highest and lowest tidal levels at the Qinglonggang station are mainly determined by the intensity of tidal forcing, and associate with the seasonal variations of the tide and river discharge. The averaged, highest and lowest tidal levels represent a landward increment feature along the North Branch. The tidal range is increased gradually from the mouth to the middle reaches of the North Branch, and decreased from its middle reaches to its upper reaches. The northerly wind in winter tends to produce an increment of the tidal level at the Qinglonggang, and the southerly wind in summer tends to produce a slight decrement of the tidal level and range there. The wind stress has almost no effect on the tidal range in the North Branch. The river discharge increases the tidal level, restrains the tide, and decreased the tidal range.

Key words: the Changjiang Estuary, the North Branch, tidal level, tidal range, impact factors