The Analysis Of The Influence Of Rainfall Runoff Pollution On The Water Quality Of Rivers

In recent years,with the development of economy and the speeding up of urbanization,the problem of water pollution has been paid more and more attention.The various economic and social problems caused by water pollution need to be resolved urgently.As the lifeblood of the economy and culture of Tianjin,the water quality of the Haihe River is related to the quality of public life and the external image of Tianjin.Therefore,it is of great theoretical and practical significance to study the pollution of the Haihe River system.In this study,the tributaries of the middle reaches of the Haihe River were taken as the study objects.The results of water quality monitoring were used to evaluate the status of water pollution and a hydrodynamic and water quality models was selected to simulate the variation of pollutant content of the typical river under different rainfall conditions,And the amount of pollutant reduction of rainfall runoff was calculated.?1?Water quality monitoring in the middle reaches of the Haihe River revealed that the river systems in the middle reaches of the Haihe River were polluted to varying degrees.The water quality of the Xijian River is most seriously polluted,and the content of ammonia nitrogen and total phosphorus is obviously higher than that of other rivers,and the other six rivers are also polluted to a certain degree.?2?The pollutant change before and after heavy rainfall was analyzed in Tianjin.It was found that except for a few cases,the trend of COD,TN and NH₄⁺-N was the same in most rivers,while the variation trend of total phosphorus in different river channels was very different after rain.?3?The single factor index method and the arithmetic average index method were used to evaluate the water quality of the middle reaches of Haihe River.The results show that the water quality of all river channels belongs to inferior V class water body and does not meet the purpose of functional area.The total phosphorus exceed the standard most seriously.The water quality of the seven rivers is the worst,and the water quality of Hongnihe River and Xingfuhe River is the best.?4?Collecting the basic data and establishing the parameters of MIKE21,such as terrain files,parameters and so on,which are needed to establish the hydrodynamic model and water quality model.The results show that the measured value agrees well with the predicted value,which indicates that the water quality model of MIKE21 can simulate the water quality of Yuanjia River more accurately.?5?The water quality of Yuanjia River under different rainfall conditions was simulated.The total nitrogen content was 6.27 mg/L and the total phosphorus content was 1.47 mg/L on the 10th day after rainfall event.Under the condition of 15-year rainfall event,Yuan simulation results The total nitrogen content was 6.35 mg/L and the total phosphorus content was 1.56 mg/L on the tenth day after rainfall.?6?The results show that for the one year rain fall event,the water quality of Yuanjiahe River needs to be reached on the 7th day of the rainy season after the rainy season.V class water quality standards,at least need to reduce the total nitrogen4605.9 kg,reducing total phosphorus 904.7 kg;for the return period of 15 years of rainfall events,at least need to reduce total nitrogen 9697.4 kg,reduce total phosphorus 1996.7kg.