Study of an abnormally strong saltwater intrusion in the Humen Channel of the Pearl River estuary

Saltwater intrusion in estuaries has become a serious environmental problem, such as in the Pearl River estuary (PRE). In this study, we used a fully validated three-dimensional hydrodynamic model EFDC to numerically investigate the saltwater intrusion in the PRE during the dry season of 2007-2008. Based on the the measured salinity, an abnormally strong saltwater intrusion occurred in the Humen Channel in February 2008. The saltwater intrusion occurred twice a month to varying extents, with each saltwater intrusion happening 1-3 days before spring tide, and the stronger saltwater intrusion always occurred at the beginning of the month. Our model results show that caused by a long-term northerly wind during the dry season, the increased steady shear term in the salt transport flux were responsible for the abnormally strong saltwater intrusion in the Humen Channel. The abnormally strong saltwater intrusion has features of long duration, far-reaching upstream distance and great hazard to freshwater resources. The wind effects were revealed to mainly influence the bottom salinity in the middle reach of the PRE, especially near the Humen outlet.