DERIVATION OF BOUNDARY CONDITION FOR QUASI-3D MODEL OF WATER EXCHANGE BETWEEN NEIJIANG AND THE YANGTZE RIVER

摘要

Neijiang is a tideland located inside the lower reach of the Yangtze River and the flow condition here is influenced significantly by tidal wave going up from the river mouth. As Neijiang connects with the Yangtze River mainly at upstream and downstream end, the numerical simulation of flow condition of Neijiang was carried out by a quasi-3D model in study area including the Yangtze River and Neijiang. However, it happens frequently that we can't get sufficient and available field data which are critical to define boundary conditions for hydraulic calculations. This paper presents a process to derive the boundary conditions for quasi-3D numerical simulation from limited available data. 1-D unsteady flow model was constructed and calibrated by using the periodic extreme value of water level in Neijiang and the hourly data of tidal level at the river mouth, and the flow rate and the water level near the tideland necessary for the quasi-3D calculation were estimated. The rationality of the calculation results were checked by the monthly flow rate at Datong, a far upstream station free from the tidal effect. Finally, by using a quasi-3D numerical model with the estimated boundary conditions, the characteristics of the water exchange between Neijiang and the Yangtze River were discussed.