A Research Of Low Impact Development (LID) Rainwater System Of A University Campus Based On SWMM

The thesis is based on the SWMM model(Storm Water Management Model)and takes the LID(Low Impact Development)as measures to conduct.According to the concept and norms of sponge city construction,a low-impact development rainwater system is constructed after research part of a university campus.Through the study of the simulated runoff flow,rainwater network overload and main pollutant concentration changes,the study can evaluate the effects which happened in the research area of sponge cities before and after simulation.In terms of simulation construction:combining the land use status,vertical elevation,rainwater pipe network and other data in the area to divide sub-catchment area and rainwater network generalization,the study area is generalized into 30sub-catchments,10 nodes,10 pipe section,and 1 discharge port.Using the Chicago rain pattern,the corresponding rainfall intensity data for the five recurrence interval periods of P=2,P=5,P=10,P=20,and P=50 were used for subsequent research simulation.In terms of LID measures,under the guidance of the program comparison,the rainwater garden was selected to be 1133 m~2,the recessed green space was 890 m~2,the permeable pavement was 4978 m~2,and the green roof was 6594 m~2.In the simulation of pollutants,the following common pollutants were selected and their initial concentrations in rainwater were set to:COD 20 mg/L,TN 1 mg/L,TP 0.02mg/L,SS 10 mg/L.The simulation results show that in the reduction of flood peaks,the decrease ratios of the peaks of the outflows after the LIDs are different from those before the LIDs:when P=2,it is 22.5%;when P=5,it is 22%;when P=5,It is 18.2%;when P=20,it is 17.3%;when P=50,it is 16.7%,which means it produced a good peak reduction effect.In terms of rainwater pipe network load,under the three recurrence periods of P=2,P=10,and P=50,the maximum drop ratio of LID to LID front node overflow and pipe network overload is 20%,50%,and 60%respectively,this greatly relieved the pressure of the rainwater network.In terms of pollution control,after take the measures of LID control,the pollution control effect is very obvious.Taking P=50as an example,the total COD(kg)removal rate increases by 51.62%,the total TN(kg)removal rate increases by 46.32%,and the total TP(kg)removal rate increased by33.50%and the total SS(kg)removal rate increased by 45.89%.This research systematically studies the scheme,simulation and evaluation of regional LID reconstruction.The research results are of great significance for constructing regional rainwater system,increasing rainwater utilization rate,and implementing the concept of sponge city construction.