A numerical study on water diversion ratio of the Changjiang (Yangtze) estuary in dry season |
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Authors: | Lu Li Jianrong Zhu Hui Wu Biao Wang |
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Institution: | (1) State Key Lab of Estuarine & Coastal Research, East China Normal University, Shanghai, 200062, China;(2) Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands |
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Abstract: | We studied the flood, ebb and tidal averaged along (net) water diversion ratio (WDR) during dry season in the Changjiang (Yangtze)
estuary, China, along with the effects of northerly wind, river discharge, tide and their interactions on WDR using the improved
version of three-dimensional numerical model ECOM. Using data for annual mean wind speed and river discharge during January,
we determined that the flood, ebb, net WDR values in the North Branch of the estuary were 3.48%, 1.68%, −4.06% during spring
tide, and 4.82%, 2.34%, −2.79% during neap tide, respectively. Negative net WDR values denote the transport of water from
the North Branch into the South Branch. Using the same data, the corresponding ratios were 50.09%, 50.92%, 54.97%, and 52.33%,
50.15%, 43.86% in the North Channel and 38.56%, 44.78%, 103.96%, and 36.92%, 43.17%, 60.97% in the North Passage, respectively.
When northerly wind speed increased, landward Ekman transport was enhanced in the North Branch, increasing the flood WDR,
while the ebb WDR declined and the net WDR exhibited a significant decrease. Similarly, in the North Channel, the flood WDR
is increased, the ebb WDR reduced, and the net WDR showed a marked decrease. In the North Passage, the flood WDR also increased
while the ebb and net WDR declined. As the river discharge increased, the flood and ebb WDR of the North Branch increased
slightly and the net WDR increased markedly. In the North Channel the flood and ebb WDR changed very slightly, while the net
WDR declined during spring tides and increased during neap tides. The WDR in the North Passage changed slightly during flood
and ebb tides while the net WDR showed a marked increase. The WDR values of different bifurcations and the responses to northerly
wind, river discharge, and tide are discussed in comparison with variations in river topography, horizontal wind-induced circulation,
and tidal-induced residual current. |
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