Water Environment Investigation And Hydrodynamic Numerical Simulation Of The Typical City Of The Upstream Of Taihu Basin

The study area is located in the west coast of Taihu, which is the upper main catchment area of Taihu River Basin.in recent years, with the development of the industrialization and city,the discharge of industrial wastewater and domestic sewage of city is increasing, finally,the pollutant flows into Taihu through the main river, resulting in exacerbating the problem of water pollution. With the goal of improving water quality in Taihu Lake, there were two aspects to study the migration of the urban water pollution and the characteristics of water flow,one was the field investigation,another was the numerical simulation.First, Made a investigation of the basin water quality in 2013 October and 2015 April, All along the river basin to set 29 monitoring points, the first one was in the upper reaches of Liyang City, and the last one was in the reaches which fanally into the Taihu River, at these points, used total nitrogen, total phosphorus, Potassium Permanganate index, ammonia nitrogen concentration as the water quality indicators, The experimental results show that the difference of permanganate index between sampling points is smaller than others. The potassium permanganate index values for4.96~6.08mg/L, total phosphorus values for 0.11~0.32mg/L, ammonia value for0.57~1.84mg/L and total nitrogen values for 2.21~4.45mg/L. According to the surface water environmental quality evaluation standards, 29 measuring point of potassium permanganate index reached a class III water standard, total phosphorus values between content between class IV and class V, ammonia nitrogen content is between class IV andclass V, some points to bad V category, the total nitrogen value content exceeded V class water standards, pollution is more serious. The total phosphorus in urban areas was the highest, while the ammonia nitrogen and total phosphorus were the highest in the entry section.Second, used the water environment simulation sofeware MIKE3 established two-dimensional numerical simulation of average vertical about the Xijiu flow field.Used this model to study the formation and characteristics of circulation in Xijiu Lake during summer. The study derived that the wind was the main factor in the formation of the summer circulation; Under the uniform effect of average time-invariant wind and terrain, the flow field downwind in shallow water while backward in deep water;Even in flat terrain, as long as the wind driving force is large enough, there would be a circulation under the effect of the Coriolis force.