Expansion Analysis And Numerical Simulation Of Minjiang Diluted Water

Minjiang River is the largest river of Fujian Province, about 6×109 m3 fresh water injects into the sea, carrying sediment, nutrients, pollutants, etc., affecting the oceanographic characteristics, water mass composition and sediment deposition of Taiwan Strait and Minjiang estuary. Minjiang diluted water expand mechanism research has a conductive meaning to relative researches, such as sediment transport, pollutants diffusion process, biological and chemical research .It also have something to do with the basic hydrology of the Minjiang estuary. In this thesis, we will study the spatial distribution and expansion mechanism of Minjiang diluted water.Based on the analysis and summarization on domestic and abroad research progress on diluted water, this thesis firstly summarized the general situation of Minjiang estuary , and we accordingly got a preliminary understanding on wind, tide, tide limit,tidal current limit,tidal prism , residual current, sediments and runoff in Minjiang estuary. Then we use the 2006-2007 in-situ data to analyze the expansion characteristics of the Minjiang Diluted Water. The analysis results showed that: Minjiang Diluted Water affected Minjiang estuary in spring and summer .Since Minjiang estuary and its adjacent waters was still reined by Fujian and Zhejiang coastal current, the extend range of Minjiang Diluted Water is difficult to define. However,from the salinity distribution we can find that the main body of Minjiang Diluted water extend southward, reach the island of Pingtan. Minjiang Diluted Water extended both southward and northeastward in summer, the main body of the Minjiang Diluted Water extended to the sea near the Sansha Bay. Fujian and Zhejiang coastal currents played an important role in Minjiang estuary and its adjacent waters in winter, Minjiang diluted water only affected the water inside the river mouth.In order to study the expand mechanism of Minjiang Diluted water; we built up hydrodynamics model and diluted water model of Minjiang estuary and adjacent waters by using FVCOM model. From the hydrodynamic simulation results we found that the flood current of Minjiang estuary came from northeast. Ebb tidal current rush eastward out of the Minjiang estuary. From the results of diluted water simulation we found that the expansion of Minjiang diluted water is affected by topography, runoff as well as wind. Eliminating the complicated topography, the expansion of Minjiang diluted water expand range is almost two times than that of only controlled by tide. When we change the amount of runoff, salinity distribution has only a little change. The wind also has a great effect on the expansion, under the Southwest wind, Minjiang diluted water no longer expanses southward, after rushing out of the Minjiang estuary, Minjiang diluted water extend northeastward. Enhancing the Southwest wind, the Minjiang diluted water is restrained. When we put northeast wind in the model, the Minjiang diluted water expand to south instead, and its affecting range is larger than before the former case.