By using the idealized estuary numerical model described in part Ⅱ of this series study, the impacts of river discharge and rise of sea level on estuarine circulation and saltwater intrusion are studied in this paper. In the case of river discharge increase, the current speed at the surface layer within the mouth increases, the land ward density induced current at the bottom layer reduces, and the point of no current moves downstream. The mouth ward density induced current outside the mouth becomes larger, and the upwelling tends to increase. The salinity intrusion within the mouth reduces, the salinity becomes lower and the area of diluted water increases outside the mouth. The salinity drops remarrably at the bottom layer and the upstream north coast of the mouth, and at the surface layer and the south coast at the mouth. The variation of river discharge has a huge influence on the saltwater intrusion. In the case of sea level rise , the land ward density induced current at the sand bar increases, the point of no current moves upstream, and the current speed becomes larger at the surface layer. The salinity intrusion within the mouth increasts, the salinity becomes higher and the area of the diluted water reduces outside the mouth. The rise of sea level has an obvious impact on the salinity intrusion, especially at the bottom layer and the north coast.
Journal of Ocean University of Qingdao