| The upstream of Liao River is an important agricultural base,and the quality of its water quality not only has a direct impact on the agricultural production,but also seriously threatens the water environment security in the basin.In recent years,with the continuous efforts of curbing the environment of Liao River,the trend of water environmental pollution degradation has been effectively controlled.However,the threat of diffused pollution to water environmental pollution has been further increased.Taking the upstream of Liao River as the study area,this paper analyzes the characteristics of diffused pollution in the study area according to the climatic and regional characteristics and water environmental characteristics of the basin.With the help of field research,The author estimates the pollution load of indicators in the basin,including COD,TP,NH4+-N,etc,and constructs the pollution load evaluation model---Arc SWAT of the upper Liao River.In order to analyze the spatio-temporal dynamic change process of rural diffused pollution,the model is used to simulate the situation of non-point source pollution in the study area.Secondly,with the SWAT-CUP model,parameters are determined and adjusted appropriately to improve the accuracy of simulation and prediction,and the concentration simulation of nitrogen and phosphorus and other diffused pollution indicators is realized.Besides,the change trend of non-point source pollution is predicted with a certain time and step length,so as to effectively reduce the total emission of pollutants in the study area and improve the quality of its water environment.By estimating the diffused pollution load in the upstream of liaohe river,we can see that the upper Liao River flows through 11 regions’ COD,TP and NH4+-N,and the annual contribution rate was 72.92%,6.47% and 20.34% respectively.Domestic sewage from poultry storage and cultivation in the basin and the discharge of various pollutants from planting cause great pressure on the upper reaches of Liao River,among which the discharge of pollutants from poultry storage and cultivation is relatively large,which counts 36.51% and 54.77% respectively.By using the SWAT model to analyze the simulation and prediction of the diffused pollution in the upper reaches of Liao River,it comes to the conclusion that in 2016,the sediment load in the upper reaches of Liao River was relatively low.In the southeast of the basin,the slope is steeper,which makes it easier to produce sediment erosion and produce more sediment.The areas with high total nitrogen load of diffused pollution are the Tongjiang mouth,Tieling,Kaiyuan,etc.The R2 values of the linear relationship between sediment and total nitrogen and phosphorus are 0.55 and 0.84 respectively.The spatial distribution of total phosphorus load is similar to that of sediment.The land use pattern and the SWAT simulation are used to analyze the situation diffused pollution of the upstream of liaohe,it can be concluded that from Kaiyuan to Tieling economic development zone and Tongjiang mouth,the total nitrogen load is higher,which is the result of the changing land use type as well as the frequently human activities.All these are the perfect illustration that the distribution of total nitrogen is closely related to the distribution of farmland.Besides,the amount of rainfall has a significant effect on the total phosphorus load.It can be concluded that the migration process of pollutants is not only affected by water temperature and erosion conditions,but also closely related to the physical and chemical morphology and distribution of pollutants in soil. |
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