Saline water and freshwater interactions in a narrow meandering channel

Abstract

Saltwater intrusion has been a global issue in water resources management and ecological engineering. This phenomenon leads to problems such as encroachment into water intake zone, loss of freshwater vegetation and disturbance to aquatic life habitat. Undeniably climate change increases the saline water flow into the river system. The meandering rivers are common, and the hydraulics is more complex than straight rivers. Experimental hydraulic research was carried out in the Universiti Teknologi Malaysia to elucidate the hydrodynamic interactions between saline water and freshwater in a narrow meandering channel. The spatio-temporal salinity profiles along the river are discussed in this paper. The findings prevailed a typical characteristic of a salt-wedge estuary and indicated the processes of estuarine mixing. As the saltwater flows upstream, the salinity level drops due to dilution process. Freshwater discharge also significantly influenced the mixing of freshwater and saline water. Velocity of saline water, Us decreased up to 25% when freshwater discharge increased for Case A and B. A rapid dilution rate was observed in Case C due to strong velocity forces produced by a high freshwater discharge. Furthermore, the interaction between freshwater and saline water in a narrow meandering river might be influenced by the flow resistance induced by the channel boundaries and meander planform itself.