Effects of varying river discharge and network geometry on net volume transport in the Yangtze Estuary, China

N.C.Alebregtse and H.E. de Swart
May 9, 2014

Many estuaries around the world consist of a network of branching channels. This presentation will focus on one such system, viz. the Yangtze Estuary in China. To understand and manage such a complex system, knowledge is required on its hydrodynamics. Here, tidal propagation and net volume discharge in the different branches of the estuary during the wet and dry season of the Yangtze River will be examined. Moreover, the effect of the Deepwater Navigation Channel (DNC) on the net discharge distribution between North and South Passage will be investigated.

By employing a 2DV semi-analytical network model, non-linear processes are identified and quantified that determine the net volume discharge through each branch. The differences between wet and dry season are investigated by prescribing different riverine inputs at the upstream boundary. Different distributions of net volume discharge over the branches occur between different seasons. The results for wet and dry season can be seen in figure 1.

Finally, the geometry of North Passage is changed from a channel resembling the bathymetry before the DNC to a channel resembling the bathymetry after the DNC. The differences with the situation prior to DNC will be identified and discussed.

Figure 1: Net volume discharge through the Yangtze estuary in wet and dry season in the left and right column, respectively. Different branches are symbolized by different colours, viz. Yangtze River by orange, North Branch by green, South Branch by cyan, North Channel by magenta, South Channel by black, North Passage by blue, and South Passage by red. Percentages are relative to river input.