Research On Joint Dispatch Of Water Quality And Quantity In The Huaihe River Mainstream Pollution Grou

With the rapid development of social economy,sudden water pollution incidents at home and abroad have occurred frequently in recent years,which have seriously affected the water quality and caused a lot of economic losses.It has become a widely concerned water environment problem.As a key measure to deal with sudden water pollution incidents,joint scheduling of water quality and quantity has always been a research hotspot in sudden water pollution incidents.Sudden water pollution incidents(or pollution group incidents)occur frequently in the middle reaches of the Huaihe River,which seriously endangers the drinking water safety and ecological environment in the middle reaches of the Huaihe River.This paper focuses on the joint scheduling of water quality and quantity in sudden water pollution incidents.Taking the middle reaches of the Huaihe River(Zhengyangguan-Bengbu Gate)as the research area,this paper investigates the historical data of the Huaihe River pollution group,analyzes the characteristics of the Huaihe River pollution group,identifies the risk sources of the Huaihe River pollution group,and designs the risk source leakage scenario.Collect and sort out the basic data of hydrology,water quality and topography,and construct a one-dimensional hydrodynamic water quality model of the main stream of Huaihe River.The dispatching effects of tributary gate(Yingshang gate),main stream gate(Bengbu gate),Yangtze-to-Huaihe River Water Diversion Project(Dongfei gate)and their combined dispatching on the pollution group in the main stream of Huaihe River were explored,and the optimal joint dispatching measures of water quality and quantity were put forward.(1)Characteristics analysis and risk source identification of pollution clusters in the mainstream of Huaihe RiverBased on the historical data of the pollution mass in the main stream of Huaihe River,it is found that the causes of the pollution mass are the discharge of tributary sewage and the discharge of industrial enterprise sewage,among which the discharge of tributary sewage is the main cause.When the Huaihe River suddenly drops heavy rain in the flood season,in order to meet the needs of flood control,a large amount of sewage originally accumulated on the tributary gate is discharged into the main stream of the Huaihe River,forming a pollution group in the main stream of the Huaihe River.The sewage sources of the pollution group emergencies caused by the discharge of tributary sewage are mainly Shaying River and Guohe River.Shaying River and Guohe River occur separately and simultaneously.The main risk sources of the pollution cluster are Shaying River and Guo River,and there is also a risk of sewage discharge in the upstream water of the Huaihe River.(2)Construction of one-dimensional hydrodynamic and water quality mathematical model of Huaihe RiverThe basic data of hydrology,water quality and topography were collected and sorted out.Based on the HEC-RAS model,a one-dimensional hydrodynamic and water quality mathematical model of the main stream of Huaihe River was constructed.Based on the water balance,the tributary flow is reasonably calculated,and the problem of missing measured data of tributary flow is solved.Using the measured data of water level,flow and water quality,the key parameters of the model such as river roughness and comprehensive degradation coefficient of pollutants were calibrated.The model calibration and verification results show that the constructed hydrodynamic and water quality model can accurately describe the hydrodynamic and water quality migration and transformation process of the main stream of Huaihe River,and can be used for the subsequent joint operation of water quality and quantity.(3)Analysis of the scheduling effect of tributary gate scheduling on the Huaihe River mainstream pollution groupFour scenarios of risk source generation were designed,including sewage generated by Shaying River,sewage generated by Guohe River,sewage generated by both Shaying River and Guohe River,and sewage generated by the upstream of Huaihe River.Three evaluation indexes of dispatching effect are put forward,including the time of pollution group leaving Bengbu sluice,the time of sensitive section exceeding the standard and the peak concentration of sensitive section.Taking the sewage generated by Shaying River as a typical case,the dispatching effect of tributary gate(Yingshang Gate)on the pollution group in the main stream of Huaihe River was analyzed.By adjusting the dispatching mode of Yingshang Gate,the sewage of Shaying River can be discharged into the main stream of Huaihe River in three ways : large flow centralized discharge,small flow slow discharge and small flow slow discharge.The one-dimensional hydrodynamic and water quality mathematical model of the main stream of the Huaihe River was used to simulate and analyze the scheduling effect of different scheduling methods on the pollution group considering the typical hydrological years.The results show that the dispatching of tributary gates has a significant impact on the pollution cluster of the Huaihe River.The smaller the discharge flow of the tributary gate,the later the pollution mass leaves Bengbu Gate,the longer the time of exceeding the standard of the sensitive section,but the lower the peak concentration of the sensitive section.When the minimum flow rate is adopted,the impact of the pollution cluster on the water quality of the mainstream of the Huaihe River is significantly alleviated,but this increases the risk of flood control in the tributaries to a certain extent.Considering the peak concentration of sensitive section and flood control risk,small flow slow discharge is the optimal tributary gate scheduling measures.(4)Analysis of the scheduling effect of the main stream gate and the Yangtze-toHuaihe River Diversion Project on the Huaihe River mainstream pollution group.Aiming at the slow discharge of small flow of tributary sewage under four kinds of risk sources,the one-dimensional hydrodynamic and water quality mathematical model of the main stream of Huaihe River is adopted.Considering the typical hydrological years of wet,flat and dry years,the dispatching effect of the main stream gate and the gate of the Yangtze River to Huaihe River on the pollution group of the main stream of Huaihe River is simulated and analyzed.Five scheduling methods are set up,including S1(background scheduling,no Yangtze-to-Huaihe River Diversion Project),S2(conventional scheduling,there is a Yangtze-to-Huaihe River Diversion Project but does not increase the flow),S3(increasing the flow of the mainstream gate),S4(increasing the flow of the Yangtze-to-Huaihe River Diversion Project into the Huaihe River)and S5(increasing the flow of the mainstream gate and the Yangtze-to-Huaihe River Diversion Project into the Huaihe River).The results show that the optimal scheduling measures are different from different scheduling effect evaluation indexes.From the perspective of reducing the peak concentration of sensitive sections,S4 scheduling is optimal;from the perspective of reducing the excessive time of sensitive sections,S3 and S5 scheduling effects are better than other scheduling.From the time of the pollution group leaving Bengbu gate,S3 and S5 scheduling effect is better than other scheduling.On the whole,the scheduling effect of S3,S4 and S5 on the pollution group is better than that of S1 and S2.