Wetland Network Design for Mitigation of Saltwater Intrusion by Replenishing Freshwater in an Estuary

In this paper, a wetland network is designed to mitigate saltwater intrusion based on the relationship between river discharge and salinity in Modaomen waterway (MDMW), the Pearl River estuary (PRE) of southern China. The designed network consists of existing and expanded wetlands, river channels and their tributaries. The freshwater stored in wetlands can be diverted into river channels to adjust salinity gradients when saltwater intrusion reaches the predefined locations. In the MDMW, two exponential regression models are established between the freshwater discharge and the saltwater intrusion length at both high water slack (HWS) and low water slack (LWS), respectively. The wetland network can effectively mitigate the saltwater intrusion when the freshwater is diverted from wetlands into river channels according to the regressive models. The method of wetland network can save over 50% more freshwater (varying from 46.1 to 56.4% at HWS and from 53.4 to 61.8% at LWS) than the emergent water allocation schedule (EWAS) implemented in 2005 to protect against saltwater intrusion in the same area. Wetland network design facilitates water resource management in the PRE and can also be easily generalized to other estuaries.