Hydrodynamic And Water Quality Modeling For The Lower Reaches Of Minjiang River

The lower reaches of Minjiang River is tidal channel network. Fuzhou city, the capital of Fujian Province, stands on the side of the river. Due to the human activities, water environmental problems are serious and the research of hydrodynamic and water quality modeling for the lower reaches of Minjiang River has theoretic and practical significance.Through investigating and appraising the current situation of hydrologic and water environment in the lower reaches of Minjiang River, the thesis makes the conclusions that a great deal of sewage drained into the river without standard disposal have bought water pollution, which is more serious in some reaches where the regionalizations of water environment function are contradictory. Excessive sand extraction and construction of Shuikou hydropower station give rise to the descending of the riverbed and even the saltwater intrusion which occurs frequently in the dry season.Based on the Saint-Venant equations describing the movement of unsteady flow and one-dimension convection diffusion equation describing the variation of contaminant concentration, using the Preissmann weighted implicit four-point scheme, one dimensional hydrodynamic and water quality models are established and applied to the lower reaches of Minjiang River. According to the simultaneous observed data, main parameters are calibrated. The results of the computation prove that the models are rational and reliable. Applying the verified models, the characteristics of low flow are numerically simulated, and the effect of excessive sand extraction is quantificationally evaluated. Comprehensive simulation and research on the contaminant concentration in the tidal river have been conducted with representative boundary conditions, including the variation of lower boundary(Minjiang River mouth) tidal types and contaminant concentration, upper boundary(Zhuqi hydrologic station) discharges and total pollution load, sewage outfalls setting and so on.