Water and Salt Transports in the Hengsha Channel of Changjiang Estuary

Rui Ma,Jianrong Zhu

doi:10.3390/jmse10010072

Abstract

In a multilevel bifurcated estuary, the channels between the bifurcated branches play important roles in the exchanges of water and salt. In the Changjiang Estuary, the Hengsha Channel (HC) connects the North Channel (NC) and the North Passage (NP). In this paper, based on a two-way nesting unstructured quadrilateral grid, finite-differencing, three-dimensional estuarine and coastal ocean model, the tidal and seasonal variations in the water and salt transports in the HC were simulated, and their dynamic mechanism was analyzed. The residual water and salt transports in the HC both flow southward from the NC to the NP. In wet season, the residual water transport in the HC is 677 m3/s during neap tide and 245 m3/s during spring tide, and the residual salt transport is 0. In dry season, the residual water and salt transports in the HC are 1278 m3/s and 0.38 t/s during neap tide, respectively, and 1328 m3/s and 12.61 t/s during spring tide. Affected by the northerly wind and the southeastward baroclinic gradient force, the water and salt fluxes in dry season are much larger than those in wet season. The dynamic mechanism responsible for the water transport in the HC was numerically simulated and analyzed.

Highlights

Estuaries, which represent the regions of transition between rivers and the ocean, are commonly characterized by intensive human activities and the interaction of multiple dynamic factors [1,2,3]
2.8% and 5.1% of the residual water transports in the North Channel (NC) and North Passage (NP), respectively
Based nesting unstructured quadrilateral grid, finite-differencing, threeBasedonona two-way a two-way nesting unstructured quadrilateral grid, finite-differencing, dimensional estuarine and coastal oceanocean model, the tidal variations in the three-dimensional estuarine and coastal model, the and tidalseasonal and seasonal variations in water and salt transports in the were simulated, and the dynamic mechanism responsithe water and salt transports in the Hengsha Channel (HC) were simulated, and the dynamic mechanism reble for thesefor transports was analyzed

Summary

Introduction

Estuaries, which represent the regions of transition between rivers and the ocean, are commonly characterized by intensive human activities and the interaction of multiple dynamic factors [1,2,3]. Tide is the most energetic source of hydropower in estuaries. The tidal range can introduce significant tide current, which oscillates the estuarine fronts and mix dissolved materials. The fresh water carried by the river and the high salt water of the open sea are strongly mixed in this area, making the estuary produce obvious density gradients in the horizontal and vertical directions, accompanied by strong temporal and spatial changes. This can produce estuary circulation under the baroclinic pressure gradient [4,5,6]

Methods

Discussion

Conclusion