The Effects of Dredging on Tidal Range and Saltwater Intrusion in the Pearl River Estuary

A dredging project in the Pearl River estuary would influence the topography, water dynamics, and mass transport process. The effects of dredging in the channel of the Pearl River estuary on tidal range and saltwater intrusion were studied using a hydrodynamic model (finite volume coastal ocean model) and historical water depth data. The measured data showed that the tidal range decreased and saltwater intrusion increased in the North River. The tidal range increased and saltwater intrusion decreased in the West River in recent decades from the 1980s. The simulations in this study showed that after dredging (1) the upstream flow split ratio in the river changed (i.e. more freshwater flowed through the Sanshui station), whereas less freshwater flowed through the Makou station; (2) the tidal range increased in the West River network and decreased in the downstream reaches of the North River network; and (3) the saltwater intrusion increased in the West River mouths and weakened in the North River mouths. These results agreed with the observed phenomenon. The change in the flow split ratio between the North River and the West River induced by dredging was the fundamental dynamic that caused changes in both the tidal range and saltwater intrusion in the Pearl River estuary.