Abstract: The construction of engineering projects in the upper reaches of the Changjiang River has changed the flow and sediment conditions of the Changjiang River Estuary and the river discharges in flood and dry seasons, which further affects the tidal current asymmetry. Such asymmetry exerts evident impact on offshore sediment transport and geomorphic evolution in the estuary. The influence of discharge regulation on tidal current asymmetry in flood and dry seasons was studied by applying a two-dimensional hydrodynamic numerical model of the Changjiang River Estuary. The nonstationary harmonic method (NS_TIDE) and tidal skewness method were applied to analyze the variation trend of flow velocity asymmetry (FVA) and flow duration asymmetry(FDA). Results manifest that tidal current asymmetry intensifies prior to a slight decrease as tidal propagates landward. The increase of discharge in dry season at the estuary not only strengthens the ebb tide dominance in the middle and lower reaches of the estuary, but also prolongs the duration of low-water slack in most areas of the estuary. In major flood period, the weakening of flood peak enhances the ebb current velocity in the middle and upper reaches and shortens the duration of low-water slack in the upstream region, while the asymmetry of tidal flow velocity and flow duration shows an opposite trend in the downstream region.

Key words: discharge regulation, tidal skewness, tidal current asymmetry, river discharge, Changjiang River Estuary