Research On Optimization Of Rainwater System And Whole Process Control Of Rainfall Runoff

The impacts of southern flood and northern drought in China have been becoming more serious in 2017.Neimenggu,Shandong and other northern provinces were constantly having drought emergency.More than 40 million acres farmland was affected by drought,and water supply was in extreme shortage in some cities.At the same time,Hunan province issued red flood warning signals.More than 4 million people's lives were affected.Southern east China has monsoon climate.Rainwater plays an important role in people's lives.If local rainwater is not regulated,the situation of uneven distribution of water resources in the southern and the northern China will be constantly worsening.In addition to reducing the water environment problems caused by the initial rainwater pollution,the northern region should also collect and use rainwater,and the southern region should increase the permeability of the underlying surface to prevent frequent floods.This paper expounds the changes of hydrological conditions before and after urbanization,the drainage principle of storm water network,and the principles of various kinds of rainfall runoff management measures.This paper compares the rainfall runoff models and their two development models used in homeland and foreign countries.Digital Water was chosen as the model of the study.This paper describes the simulation process of Digital Water,and introduces the principles of hydrological simulation,water quality simulation and hydraulic simulation respectively.The basic situations of studied area were summarized,the general conditions of local hydrology,water resources,and water environment are emphasized in the study.The model was constructed by Digital Water.The deterministic parameters were generalized,and the uncertainty parameters were calibrated,and the sensitivity analysis was carried out.A relatively accurate rainwater runoff management model was established.The domestic and international design standards of rainwater system were compared and analyzed,with emphasis on the similarities and differences amongChicago rain pattern,rectangular rain pattern,triangle rain pattern and Huff rain pattern.Focusing on the specific rainfall situation in the study area,the study analyzed the operational aspect of regional rainwater system in eight rainfall scenarios,and found that the influences of runoff of different rain types varied greatly.The rectangular rain pattern,which is often used in rainwater pipe network design,had the least impacts on the rainwater system.According to the influences of eight rainfall pattern on rainwater system,the corresponding optimization measures were proposed,so that rainwater system can adapt to the influence of different rainfall conditions.It was found that the design of rainwater system should consider not only the estimated water flow and rainfall return period,but also the impacts of different rainfall conditions in the study area.The rainfall runoff simulation in the study area is necessary for large and complex storm water system.The whole process control of rainfall runoff was briefly introduced.The effects of source control measures,process control measures,end control measures and whole process control on rainfall runoff management were studied and analyzed respectively.The simulation study of permeable pavement,biological retention facilities and its combination scheme showed that the control efficiency of biological retention facilities on each parameter was greater than permeable pavement.The combination of the two measures had positive control effect on rainfall runoff.The reduction rates of runoff coefficient,runoff peak and total runoff were more than 30%,and the total reduction rate of pollutants was more than 60%.The initial rainwater discharge patterns were studied under the principle of equal-time flow,and it was found that the constant volume initial rainwater discharge facility had higher control efficiency on the initial rainwater pollution.Simulation results indicated that initial rainwater drainage facilities could not cut on pollutant concentration of initial rainwater,but the total amount of pollutants were able to be controlled by discarding the polluted water in the early stage of rainfall.The facilities also reduced the total amount of runoff and the peak value of runoff.The results showed that the storage tank could effectively reduce the peak value of runoff and the total amount of pollutants,and the total reduction rate of pollutants was more than 30%.Combining the source control measures,process control measuresand end control measures,it was found that the three types of control measures had different contribution rates to each evaluation parameter,and the combination measures had good applicational effect.In the actual engineering application,different runoff management control measures have different application scope,which can make up for each other,and make the control rate of rainfall runoff management reach the maximum.