Health Assessment Of Urban Water Cycle During Stormwater Runoff Processes

With the acceleration of urbanization,the non-point source pollution and flood disasters are getting worse.Because the initial storm runoff urban process effects on urban water cycle in a short-term remarkably,thus the rainfall process is critical for urban water circle.On this background,this study focused on monitoring and evaluating the urban water cycle during stormwater runoff processes.Diverse research methods including concept analysis,evaluation model construction,scheme implementation,case analysis was applied.Based on the analysis of the structure of the urban water cycle during stormwater runoff processes,an attempt was made to define its concept.Using the Analytic Hierarchy Process(AHP)and Key Performance Indices(KPI)principle,a model of health assessment for urban water cycle during stormwater runoff processes was established.In order to provide basic support for evaluation,an implementation plan was formulated combining experimental monitoring with urban stormwater mode.In addition,five typical rainfall events of different magnitudes from 2017 to 2018 in Handan were selected for case analysis.The main contents and results of this study are as follows:(1)Defining the concept of health urban water cycle during stormwater runoff processes: important domestic and international researches on health assessment of urban water cycle were reviewed.Based on the current phenomenon of urban waterlogging and serious non-point source pollution,the features of health urban water cycle during stormwater runoff processes were displayed.By analyzing the circulation structure of the water cycle and selecting the key processes that affect its health,an attempt to define the concept of health urban water cycle during stormwater runoff processes was made.(2)The construction of the evaluation model and the implementation plan.Based on the analysis of the above concepts,the evaluation system was determined using the Analytic Hierarchy Process and Key Performance Indices,which included 3 levels,4 dimensions,and 11 indicators.The grade description method was used to determine the evaluation threshold of the indicator.According to the differences of several index dimensions,the index was divided into 5 evaluation levels.The relative importance of each index element was described based on the pairwise comparison method.An evaluation model of urban water cycle during stormwater runoff processes was established through determining the weight value of the index to its dimensional layer by constructing a judgment matrix.On the basis of the evaluation model,an implementation plan was developed which included monitoring trials and SWMM model to provide data support for evaluation.(3)Health assessment of urban water cycle during stormwater runoff processes in Handan city: The study took Handan City,Hebei Province as the research area,selected 5 rainfalls of different magnitudes,and analyzed the rainfall characteristics over the years in Handan metropolis.The monitoring experiment of stormwater runoff processes in Handan city was carried out and the SWMM model was constructed for data simulation.Based on the results of monitoring and simulation,the model of health assessment of water cycle in research area was built.The evaluation results of light rain and moderate rain both were sub-health.The results of heavy rain and above were ill.The scores are 3.21,3.48,3.96.The relationship between the evaluation results and rainfall was logarithmic.In the dimension evaluation results,the Runoff Generation is a key link that affects the health of urban water cycle during stormwater runoff processes.In the evaluation results of the index layer,the Regional Water Environment Capacity and Stream Structure scores are low,indicating that the channel shape and water quality in the study area are significantly affected by artificial disturbance.The study has enriched the concept of urban water cycle health and provided technical support for assessing the health of the water cycle during stormwater runoff processes and reference for the sustainable development of different cities.The evaluation results of case study provided statistic support for improving regional water cycle health and optimizing regional water conservation management.