Research On Scale And Distribution Of Rainwater Storage Tanks In Urban Water Treatment Based On SWMM And MIKE11 Model

With the rapid development of urbanization,in order to solve the problem of urban rivers being affected by rainwater runoff pollution,this study selects the Jiehao River area of Jieshou City as the research object,and establishes the study area SWMM rainfall runoff model and MIKE 11 hydrodynamic water quality model to understand the changes of the main pollutants COD and NH₃-N of the Jiehao River,and simulates and analyzes the improvement of the water quality of the Jiehao River under different locations,different construction volumes and different combination schemes of rainwater storage tanks,and the determination of the best construction plan for the rainwater storage tank.The main contents and conclusions of the research are as follows:（1）Based on the SWMM model,the surface runoff in the Jiehao River area was simulated and studied.According to the land use type,pipe network map and road network map of the study area,the catchment area and rainwater pipe network of the study area were roughly generalized,and the SWMM rainfall runoff model of the study area is established to simulate the rainfall runoff under three different rainfall conditions in the study area.The simulation results show that under different rainfall conditions,there are some differences in the change of water quantity and quality of rainwater outlet.Under the condition of return period P=1 rainfall,the simulated value of rainwater outfall is in good agreement with the actual monitoring value.The discharge evaluation index NSE=0.713,R=0.935,COD evaluation index NSE=0.705,R=0.916,which indicates that the model established under the condition of 1-year rainfall can basically reflect the rainwater discharge of Jiehao River catchment.（2）Based on the MIKE11 model,the water quality change of the Jiehao River was simulated.The simulation data of the rainfall runoff model is applied to the MIKE 11hydrodynamic water quality model,and the water environment change model of the Jiehao River is established to simulate the changes in the concentration of COD and NH₃-N.The measured data of flow rate,COD and NH₃-N concentration of JHH-4#at the monitoring section of Jiehao River were fitted and analyzed with the simulated data of the MIKE11 model.The results show that the correlation coefficients between the simulated and measured values of flow,COD and NH₃ respectively:0.841,0.862,0.884,indicating that the simulation results have a high degree of fit with the measured data,the simulation results are reliable,the model can basically reflect the temporal and spatial changes of the hydrodynamic force and water quality of the Jiehao River.（3）Based on the established rainfall runoff model and MIKE11 water quality model of the Jiehao River area,the simulation and analysis of the rainwater storage tanks under different construction positions,different construction volumes and different combinations of plans for the improvement of the water quality of the Jiehao River under rainfall conditions.The research results show that,taking into account the land supply and economic benefits,the construction of a 10000m³rainwater storage tank at the end of the drainage network of the Jiehao River area can meet the effective control of rainfall runoff pollution in the study area,and the average concentration of COD in river sections decreased by 20.6 mg/L,and the reduction rate was 36.5%;the average concentration of NH₃-N decreased by 2.19 mg/L,and the reduction rate was 44.7%,and the comprehensive benefits were the best.（4）According to the simulation results of the model,it can provide a basis for the design of the Jiehao River non-point source pollution control project,and provide scientific guidance and reference for the pollution control of similar urban rivers polluted by non-point sources.