Study On Risk Assessment Of Non-point Source Pollution In Daqing River Basin Using SWMM Mode

In recent years,all parts of the country have conscientiously implemented the decisions and plans of the Party Central Committee and the State Council,and have been deeply engaged in the battle for the protection of blue water,resulting in a marked improvement in the quality of the water environment nationwide.However,pollution from agricultural surface sources in some areas is becoming a major constraint on the sustainable improvement of the water environment.The Daqing River flows through the main agricultural production areas in the North China Plain,and the potential risk of agricultural surface source pollution is high.Therefore,it is of great significance to scientifically assess the agricultural surface source pollution of the Daqing River,investigate and grasp the intensity,causes and spatial distribution of the pollution,and then provide scientific suggestions on control and management measures.Agricultural surface pollution is scattered and lagging,and its scientific assessment has always been a major challenge in the environmental field.In this paper,we propose a method for evaluating the risk of surface source pollution based on the SWMM(Storm Water Management Model)model,taking nitrogen(TN),phosphorus(TP)and chemical oxygen demand(COD)as the objects of study,analyse the main causes of agricultural surface source pollution discharge in the river,assess the risk level of surface source pollution in the river and its spatial distribution,and The study aims to provide scientific and technological support for the monitoring and management of agricultural surface source pollution in the Qinghe River.The main research contents and conclusions of this paper are as follows.(1)Estimation of the equivalence load of surface source pollution in the Daqing River from 2019 to 2020.An improved runoff splitting method is proposed based on the correlation between runoff flow and surface source pollution load to analyse the baseflow flux and load flux of the Daqing River.The results show that among the surface source pollutant discharges,fertilizer application,livestock farming,rural domestic sewage and aquaculture account for 92.72%,6.44%,0.22% and 0.62%respectively,with fertilizer application becoming the main source of surface source pollution in the Daqing River.(2)Analysis of the risk level assessment of surface source pollution in the Daqing River from 2019 to 2020.Based on the multi-factor integrated evaluation method and SWMM model,the risk of surface source pollution in the Daqing River was evaluated by grading through principal component-cluster analysis,and the sub-catchment areas M1-M60 were divided into three grades.The ecological vulnerability of M8,M15,M43,M51 and M54 is between 0.904 and 1,which belong to the key source area of surface source pollution and the potential risk of surface source pollution is more prominent.(3)Simulation of the effect of surface source pollution control measures in the Daqing River.The reduction of pollutants was simulated for the common prevention and control measures of returning farmland to forest,scientific fertilisation and comprehensive prevention and control,of which only the sub-catchment M9 was suitable for the returning farmland to forest measure;the reduction rates of TN and TP pollutants in the Daqing River from scientific fertilisation were 4.87% and 14.69%respectively;the reduction rates of TN,TP and COD pollutants from comprehensive prevention and control measures reached 4.47%,15.51% and 0.26%.The results show that the integrated prevention and control measures have shown good effects on the pollution load reduction of the Daqing River,and the implementation of integrated prevention and control measures may be a proven method to control the surface source pollution of the Daqing River.