| In China, Taihu Lake is the third largest freshwater lake, and with the quick development of the river basin, Taihu Lake water environment present a bad trend that down a notch in every10years. Master the nutrient content, grasp the water environment mechanism, and make some simulation and prediction, it may have a guiding significance to curb the water environment continues to deteriorate, reducing the level of eutrophic water environment, provide technical support and decision support for water environment management,This paper collects the measurements of Taihu Lake, considering the effects of implementation of the Water Transfer Project from Yangtze River to Taihu Lake on the hydrodynamic and ecological impact of Taihu Lake, based on Environmental Fluid Dynamics Code (EFDC) model, building a two-dimensional ecological dynamic model, simulating the Taihu Lake water environment ecological process along with the change of time and space,doing calibrtion,validation,and some analysis of Taihu Lake.The main research results (1) Simplify the inflows around the Taihu Lake. Article15big rivers on behalf of Taihu lake inflow boundary, and the simulation results is very satisfactory, the simplification of Taihu lake is reasonable and acceptable;(2) Study the flow of Taihu lake, considering the effect of implementation of the project about water diversion from Yangtze River to Taihu lake in recent years, establish a suitable water flow characteristics of water dynamic model, take both wind current and throughput flow into consideration, the result shows that the project had little impact on the flow of Taihu lake;(3)Taihu Lake two-dimensional hydrodynamic model is of high simulation accuracy, the water level simulation of daily average deviation within2cm, and average error of water temperature is within2℃, the lake flow simulation condition is the same as the predecessors’ research results;(4) Taihu Lake two-dimensional water quality and ecological dynamic model’s simulation result of time and space data can meet the requirements of forecasting, early warning, etc. The highest simulation accuracy is DO and COD index.NH4, TP and Chla index’s simulation effect is good. TN index’s simulation was within acceptable range in addition to the summer;(5) According to model of water quality, ecological related parameters of running, summed up sensitive parameters of each nutrient, and the correlation between multiple parameters. From the results of this study, we can summarize that:(1) Taihu lake has a large area, the water ecological environment is very complicated, so the velocity, temperature and sediment release quantity are different in different regions, lead to the nutrient concentration has significant spatial difference in different parts.(2) low amounts of algae in the lake district had no obvious linear correlation with TN and TP concentration; And algae outbreak area has obvious linear correlation with TP concentration, also has correlation in some extent with TN concentrations. The optimal environment of algae growth, TP concentration is0.15～0.35mg/1, TN concentration for2～2.5mg/1, TN/TP ratio of5to15;(3) Low concentrations of TN and TP has a promoting effect for algae growth, when the TN and TP concentration reaches to a certain value it will restrain the growth of algae. So in the management of the lake eutrophication problem, not only devoting to N, P content reduce, but also should be focus on the phenomenon of algae blooms reply by reducing TN and TP concentration.(4)Taihu lake water ecological environment model is established based on EFDC model, simulation of Hydrodynamic model has a high precision, water level simulation error in0.62%, and water temperature error within18.5%. water-ecological dynamic model simulation error is within30%.The results suggest that using EFDC model simulate Taihu Lake water environment has a certain feasibility, be able to provide technical support and decision support of management,prevention and control work about Taihu Lake. |
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