Simulation And Risk Assessment Of Non-Point Source Pollution In Shitoukoumen Reservoir Catchment

Shitoukoumen reservoir is a large controlling water conservancy project in middle reaches of Yinma River which is an important tributary of the second Songhua River,and is the main water supply source area in Changchun,so the water quality of the reservoir is also very important and prominent.In recent years,with the economic and social development in Shitoukoumen Reservoir Catchment,many problems of water pollution have emerged in Shitoukoumen Reservoir Catchment.Among them,the problem of non-point source pollution is particularly serious.The serious non-point source pollution not only is a serious threat to drinking water and agricultural irrigation water security,but also restricts the sustainable economic and social development of Shitoukoumen Reservoir Catchment.Therefore,to aim at non-point source pollution of Shitoukoumen Reservoir Catchment,it is urgent to carry out simulation research and risk assessment on non-point source pollution in order to provide a scientific basis and decision support for controlling non-point source pollution in Shitoukoumen Reservoir Catchment.Shitoukoumen Reservoir Catchment was selected as study area in this paper.This paper carried out six aspects of research in Shitoukoumen Reservoir Catchment.First,this paper collected the basic data of the research area to acquaint the overall situation of the study area.Sceondly,this paper applied of 3S(GIS,GPS,RS)technology to establish the Shitoukoumen Reservoir Catchment database.Thirdly,according to the actual situation of non-point source pollution in the study area,this paper established the SWAT simulation model of non-point source pollution in the study area.And the simulation model is used to calculate the annual incoming river load of non-point source pollution in the study area and analyze the spatial distribution characteristics of non-point source pollution.Fourthly,according to the actual situation of Shitoukoumen Reservoir Catchment,this paper established the non-point source pollution risk assessment system to carry out risk assessment of non-point source pollution in Shitoukoumen Reservoir Catchment.Fifth,according to the risk assessment results and spatial distribution of non-point source pollution,the study area was divided into pollution control zones,protected area and protection area.Lastly,according to the results of non-point source pollution control zoning in the study area,this paper put forward three non-point source pollution control measures for deep application of chemical fertilizer,setting of vegetation buffer zone and returning farmland to forest of sloping land in the controlling area.And this paper use the SWAT model to predict the burden reduction effect of control measures.This paper obtained the following results.(1)In the study area,the annual average load of non-point source nitrogen is 6457t,and the annual average load of non-point source TP is 527.20t,and the annual average load of river sediment is 135.69×10~4 t.There is a significant positive correlation between the load and annual rainfall of non point source pollution.(2)The zone with larger output intensity of total nitrogen output mainly distributes in upstream and midstream of Shuangyang River and the middle reaches of Yinma River and Chaluhe River.The total phosphorus output and sediment output has the similarity in the spatial distribution.And the zone with larger output intensity of total phosphorus output and sediment output mainly distributes in the zone with strong human activity intensity and slope land concentrated areas,and the zone is the key area of soil erosion.(3)The non-point source pollution risk assessment results show that the high risk areas mainly distributes in the upstream and midstream of Shuangyang River and in the middle reaches of Yinma River.And the low risk areas mainly distributes in the vicinity of the Shitoukoumen Reservoir and the southeast of the study area.(4)The results of non-point source pollution control zoning in the study area show that the pollution control zones mainly distribute in the upstream and midstream of Shuangyang River and in the middle reaches of Yinma River.The intensity of human activities is strong in these zones,and the agricultural areas are concentrated in these zones.In addition,the upstream of Xingxingshao Reservoir with large terrain slope and high soil erosion risk also belong to the pollution control zones.(5)The prediction results of non-point source pollution control measures in the study area show that the three non-point source pollution control measures proposed in this study have obvious effect on the reduction of non-point source pollutants in the study area,and the response effect of setting up the vegetation buffer zone is the most obvious.