| The utilization of urban rainwater resources is an important approach to solve the shortage of urban water resources,relieve the pressure of flood control,keep the groundwater and improve the ecological environment.The utilization of rainwater resources combined with sponge cityc can not only achieve benefits of economic,but also benefits of technology,ecology and society.This paper takes the main urban area of Dalian as the study area.On the basis of the analysis of the current situation and demand of urban area,we developed the goal of rainwater utilization and studied the optimization of rainwater utilization measures.Furthermore,the effects and comprehensive evaluation of rainwater resources utilization were studied.The main research results are as follows:(1)Based on the analysis of the current situation and utilization demand for rainwater in the main urban area of Dalian,this paper established the corresponding utilization targets and the indexes for further analysis.The control rate of annual rainfall volume is not less than 70%.Furthermore,the utilization rate of rainwater is not less than 5%,and 60% for the the pollution reduction rate of annual rainfall runoff.(2)The appropriate technology and adaptation measures were selected according to the actual situation of the main urban area.Firstly,eight kinds of measures on low impact development were chosen for this study area.Secondly,five schemes were developed by combing,simulating and adjusting the measures.The the fuzzy optimization method was used to get the better one form the five schemes.In this method,the cost,volume reduction of rainfall runoff,pollution reduction rate of rainfall runoff and effects of ecological landscape were used as the indexs.(3)The effects of rainwater utilization were analysed through qualitative and quantitative analysis in the main urban area of Dalian.The results show that rainwater utilization can reduse the volume of urban water supply and relieve the pressure from flooding.Furthermore,the utilization of rainwater can help to supply the groundwater,reduing the seawater intrusion,which has great effect on the ecological environment.The evaluation indexs were established through the classification and synthesis of many indicators.The variable fuzzy set evaluation model was selected as a comprehensive evaluation model of the rainwater resource utilization scheme,and the method of determining the index weight was improved to make it more applicable to the rainwater resources utilization scheme under new condition.(4)The area near Labor park in the main urban area of Dalian was chosen as the typical research area.Firstly,the utilization targets and the indexes were established on the base of the analysis of present situation and the demand,and then the appropriate rainwater utilization measures were recommended.Furthermore,five schemes were proposed to meet the requirements of the target,and the fuzzy optimization method was used to optimize the scheme.The membership degrees of the five schemes are 0.43,0.63,0.55,0.67 and 0.78,respectively.The final scheme was chosen according to the highest optimal membership degree.Secondly,the effects of the final scheme on urban water supply,flood control,groundwater conservation and ecological environment were analyzed.The results show that the study area can save the urban water supply about 126,000 m3 each year,and save water costs about 441,000 yuan.Furthermore,the scheme can effectively control the total rainfall runoff and peak flow;also relieve the pressure of flood control.The scheme has great effect on groundwater conservation by recharging groundwater about 54,000 m3 each year,and the recharge rate has increased by 67% relative to the present situation.So the scheme ecological environment will be significant improved.Finally,the final scheme is evaluated with the comprehensive evaluation model of rainwater resources utilization. |
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