| There is a serious shortage of water resources in China,and the serious water environment pollution aggravates this problem.On the other hand,due to the time and space differences of precipitation distribution in some areas of China.drought and flood disasters may attack the same area in turn under extreme weather conditions,resulting in economic losses and environmental damage.The efficient collection and utilization of rainwater of the sponge city can break the uneven distribution of regional precipitation in time,it can simultaneously improve the ability of drought resistance and drainage,then alleviate the shortage of water resources in China.The application of constructed wetland in sponge city achieve various functions to solve the above problems.In order to implement the requirements of the construction of ecological civilization,the sponge city project which targets to enhance its capacity of rural flood control,drought and drainage,has became a new hot spot in the field of urban construction engineering in recent years.In addition to flood control and drainage functions,sponge city project is also an effective method to achieve multiple goals of urban water ecological environment restoration and improvement.Therefore,the construction of sponge city project has very positive significance for flood disaster-prone areas in southern China.Under the above research background.constructed wetland can not only play a role in rainwater storage and physical purification of pollutants with Low Impact Development(LID)facilities in the construction of sponge city projects,it can also remove pollutants from rainwater runoff by biochemical treatment under stable operation conditions.The purified rainwater can reach the similar quality level of surface water.Therefore,the function and effect exploration of constructed wetland in sponge city construction project has positive significance to ecological civilization construction while conforming to the latest research trend.SWMM(storm water management model)is the major research tool in the field of sponge city engineering.Therefore,this study takes advantage of the quantitative analysis method to establish the SWMM analysis model with the central area of Wuyishan City as the research background.First,get the related information from the local satellite image and planning design data of Wuyishan City.accordingly set up all the geographic information of the SWMM model research area.Then simulate the precipitation intensity distribution of the preset situation according to the local rainstorm intensity formula of Wuyishan,and complete the input of precipitation information of the model.According to the types of land use in the study area,set the surface accumulation and scour function of pollutants in the sub catchment area.When all the parameters of SWMM model have been setted,SWMM model can simulate the precipitation process and show the results of runoff and pollutant emissions.According to the simulation results of SWMM software,find the sub area with the most serious water logging phenomenon in the study area.and choose it to be the simulation area of sponge city construction.In the selected water logging subarea,three kinds of LID facilities(porous pavement,sunken green land and constructed wetland)with the equal area proportion will be setted and simulated in succession.After analyzing and comparing the reduction of runoff and total discharge of pollutants,it is found that the constructed wetland has played a better role among three kinds of LID facilities.The above research extends the function of LID unit in SWMM model.and create innovative designs according to the local situation of Wuyishan City,then conduct a variety of innovative research accordingly.First simulate the total nitrogen advanced biochemical treatment of rainwater wetland,referring to the related research results in the field of sewage treatment.The relevant data are screened by the value of influent carbon/nitrogen ratio,and the data source fitting equation with the closest influent carbon/nitrogen ratio is finally selected.The minimum discharge value of total nitrogen concentration in effluent of constructed wetland is obtained by simulation calculation when the reaction time is sufficient.Then calculate ecological benefit of LID units,according to the ecological benefit calculation formula which based on the ecological economic theory.The calculation results show that the ecological benefit of constructed wetland is at a high level among LID facilities,so it has higher ecological economic value.Finally,according to the current situation of drainage system in China,explore the feasibility of taking advantage of constructed wetland as the combination point of gray infrastructure and green infrastructure,to realize the optimal allocation of municipal facilities resources.Through the research,it is found that in the sponge city project,the constructed wetland has significant functions in rainwater runoff retention and purification.Its ecological economic value,as well as the promotion of combining of gray and green municipal facilities can not be ignored.This study shows that as a combination of green municipal infrastructure and gray municipal infrastructure,constructed wetland has a certain innovative significance for the efficient use of municipal infrastructure.This study also quantifies the eco-economics value of LID facilities such as constructed wetlands,which provides a new evaluation index for sponge city engineering construction,and complements the relevant theories of sponge city construction at the eco-economics level,as well as further enriching the relevant content of eco-economics theory.On the one hand,this study analyzes and evaluates the functionality of constructed wetlands from multiple perspectives,and the evaluation results can clarify the functional orientation of constructed wetlands in sponge city engineering,which has great significance for scientific decision in sponge city engineering practice. |
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