Analysis And Research On Influencing Factors Of Lake Water Environment

The "Overall Plan for the Ecological Green Integrated Development Demonstration Zone in the Yangtze River Delta" published on the website of the National Development and Reform Commission on November 19,2019 pointed out that the "one river and three lakes" of Taipu River,Dianshan Lake,Yuandang Lake,Fen Lake should be the focus,and comprehensive management of the ecological environment has put forward higher requirements for the management of Yuandang Lake.However,at present,there are few domestic studies on the water environment of Yuandang Lake,and often only focus on the impact of shore pollution sources on the water environment of Yuandang Lake,ignoring Yuandang Lake influence of natural attributes and Dianshan Lake top support on the water environment.Based on this background,this paper established a two-dimensional water environment model of Yuandang Lake by using EFDC water environment model,combined with the basic data of hydrometeorology,physical geography,hydrodynamic quality and other data of Yuandang Lake,and analyzed and studied the influence of wind field,temperature,internal and external source pollution and the top supporting effect of Dianshan Lake on the water environment and water ecology of Yuandang Lake in different seasons.The hydrodynamic model is used to simulate the flow field distribution and water body movement in Yuandang Lake under the influence of wind field and the top support of Dianshan Lake.A water quality model of Yuandang Lake was established to simulate the concentration distribution of TN and TP under the influence of different wind fields,temperature,internal and external source pollution and the top supporting effect of Dianshan Lake,and to explore the influence of these four factors on the water quality of Yuandang Lake.Based on the above research,some suggestions on water environment management of Yuandang Lake were put forward.The research results are as follows:(1)Lake velocity is greatly affected by wind speed,and the greater the wind speed,the greater the lake velocity.Wind speed mainly affects the flow velocity of Yuandang Lake,and wind direction affects the quantity,direction,size and location of lake circulation.Under the condition of the same wind speed,the overall flow velocity of Yuandang Lake in autumn and winter is higher than that in spring and summer,and the water mobility and exchange capacity are better,and summer is the weakest.The higher the wind speed,the stronger the fluidity of water,the faster the diffusion of pollutants,the greater the concentration of the decline.In spring and summer,due to the low flow rate in the middle of the lake,the water mobility is weak.In autumn and winter,TN and TP diffused to the whole lake.In particular,TN and TP in Yuandang Lake completely spread to the whole lake under the influence of summer typhoons,but the typhoon lasted for a short time and the decrease of pollutant concentration was small,which was one of the reasons for the poor water quality in Yuandang Lake in summer.(2)Temperature has almost no effect on the structure of TN and TP concentration field,but has a great influence on the concentration value.The higher the temperature in the same region in the same season,the higher the concentration value of TN and TP.Temperature is one of the factors affecting the release rate of nitrogen and phosphorus elements in lake bottom mud,which leads to the increase of TN and TP concentration.(3)Fishery aquaculture pollution has a great impact on the water environment of Yuandang Lake,and the best effect can be obtained through the reduction simulation of fishery aquaculture pollution.(4)The water of Dianshan Lake enters Yuandang Lake from the sky breach and forms a circulation in the central and western part of Yuandang Lake due to the roof supporting action of Dianshan Lake.The greater the discharge from Dianshan Lake to Yuandang Lake,the lower the velocity of circulation area.This is because of the collision between the flow of the summer tide into the lake and the flow of Yuandang Lake from west to east,energy offset,resulting in slow flow,the more the flow of tide into the lake,the higher the offset degree.Due to the supporting effect of Dianshan Lake,the largest drainage outlet of Yuandang Lake,Tiankuikou,changed from exiting the lake to entering the lake,and pollutants could not be discharged.Dianshan Lake water entered Yuandang Lake,which brought more TN and TP to some extent,resulting in a further increase in the concentrations of TN and TP in Yuandang Lake.(5)The simulation analysis results show that in the water environment treatment of Yuandang Lake,the pollution treatment of fishery breeding should be the most important,followed by the treatment of domestic pollution,and the influence of Dianshan Lake on the water environment of Yuandang Lake should be considered comprehensively,and the simultaneous treatment should be carried out.