The Simulation Research Of Agricultural Non-point Source Pollution Under Different Fertilization Scenarios In Dianchi Watershed Based On SWAT Model

In recent years,Dianchi Lake water pollution problem is increasingly serious,the non-point source pollution is one of the main sources of water pollution.the non-point source pollution is affected by many factors,in which the irrational fertilization is an important source of non-point source pollution.In the study the Dianchi Watershed was selected as the research area,and the SWAT model was used to simulate the agricultural non-point source pollution.By setting different fertilization scenarios to analyze the relationship between fertilization and agricultural non-point source load,which provides scientific basis and decision support for alleviating agricultural non-point source pollution and rational fertilization in Dianchi Watershed.Meanwhile,the study analyses the agricultural non-point source pollution load output,the distribution of temporal and spatial,and the load output of different land use types,which is of great significance to the source control of agricultural non-point source pollution in Dianchi Watershed.The main contents and research results are as follows:(1)Using ArcGIS,SwatWeather and SPAW to process the land use data,soil data and meteorological data of the Dianchi Watershed,establishing the basic database of Dianchi Watershed for SWAT model.According to the actual characteristics of DEM and river network distribution.The whole Watershed was divided into 102 sub-basins and 261 hydrological response units(HRUs).(2)Using SWATCUP 2012 and the runoff data of the watershed hydrological station to calibrate and validate the runoff parameters of the model,the R2 and Ens parameters of the calibration and verification periods all meet the accuracy requirements of the SWAT model.The model simulates the agricultural non-point source pollution in the watershed has a good adaptability.(3)Through analyzing the simulation results of agricultural non-point source pollution by SWAT model,the results show that the agricultural non-point source pollution are mainly distributed in the middle of the watershed,and the distribution of the northern and southern regions is less,and the rainfall and land use determine the pollution load.(4)For three rotation land of the study area,the study set three different fertilization scenarios to simulate the agricultural non-point source pollution in the study area.The results show that there is a significant positive correlation between the output of agricultural non-point source pollution load and the fertilization amount,and the change of total phosphorus load output is more significant.In the analysis of various forms of nitrogen load output under different fertilization scenarios,the change of nitrate nitrogen was the largest in all kinds of nitrogen load,while organic nitrogen and nitrogen have no effect.Therefore,in order to reduce the agricultural non-point source pollution load,we should pay attention to reasonable scientific fertilization,which is not only to ensure crop yield,but also effective control of the environment pollution.