Salt intrusion response to changes in tidal amplitude during low river flow in the Modaomen Estuary, China

Abstract

Because of the increasing of water demand in the recent years, the salt water intrusion in Modaomen Estuary becomes severe which influences water supply in the surrounding regions, especially the cities of Zhongshan, Zhuhai in Guangdong Province and Macau. The variability of salt transport determines the variation of the length of the salt intrusion in an estuary. Numerical model of Delft3D flow was using to study the salt transport mechanisms and the response of salt intrusion to changes tidal amplitude. The total transport pattern shows the salt intrusion changes corresponding to spring – neap tide variations. The total transport shows a net landward transport during neap tides and seaward transport during spring tides the response of salt intrusion to change in tide amplitude depends largely on river flow. The salt intrusion length changes very little with spring-neap changes in tidal amplitude during a persistent period of low river discharge, whereas the salt intrusion changes significantly during fortnightly cycles under high flow conditions.