Research On Hydrodynamic Environmental Impacts Of Proposed Projects In Changjiang Estuary During Dry Season

To meet the demand of navigation, fresh water supply, flood prevention, irrigation, drainage and longshore development, the progress of regulation projects in Changjiang Estuary goes faster and faster. The revolution of Changjiang Estuary will take place after projects in nearly 20 years.In this paper, natural environment, hydrological conditions and river regime characteristics are discussed. Methods for establishing tidal and salinity numerical model are studied. A 2D numerical model from Jiangyin to nearshore of Changjiang River was established by Delft3D. Comprehensive influence by multiple projects on flux, flow velocity and direction, water level and salinity was calculated.The results show that total flood volume will decrease 17.4%, and ebb volume will decrease 18.8% in dry season after regulation projects in the Estuary. Split ratio of the North Channel will increase, while other channels will decrease. The project to narrow the North Branch will reduce the storage capacity for tidal water. This will be benefit for ebb tidal volume increasing and flood tide decreasing at the mouth of North Branch. However, the flood tidal volume is still larger than that of ebb tide. Area at the mouth of Changjiang Estuary will become more sensitive of water rise up in open sea after projects. The projects can effectively suppress the direct saltwater intrusion, but ineffective to prevent saltwater intrusion from North Branch.