Research On Rainwater System Design Of Small Towns In Arid Zone Under LID Measure

Water resources are extremely valuable in arid areas.However,the drainage networks in small towns are always damaged or at a backward level,or there is no special drainage system at all.As a result,Rain Water runoff cannot be discharged in time during the peak period,which not only increases the probability of urban waterlogging,but also wastes valuable rain water resources.The small towns in arid area have very small rainfall and a great amount of evaporation,coupled with economic backwardness and incomplete urban engineering infrastructure such as Rain Water system,so drought and waterlogging coexist in this area.To solve this problem,this paper first discusses the current situation of rainwater system at home and abroad,including the current research focus and dynamics of rainwater management,and analyzes the existing problems of rainwater system in small towns in arid area.Secondly,this paper systematically discusses the application principle and flow of LID(Low Impact development(low impact development)measures in rainwater system planning.This paper gives a comprehensive analysis about the site condition analysis,the establishment of control objectives and indicators,the selection and optimization of construction land,the selection of LID application mode,the selection of low-impact development measures,the layout of facilities,the maintenance and management of measures,etc.Finally,based on the above research,this paper takes the rainwater system improvement design planning of Wangtuan Town,Tongxin County,Ningxia as an example,and applies the LID measures to verify the theory of LID measures in fact.At the same time,the SWMM model is used to simulate the process of improving the design of rainwater in Wangtuan Town,in order to test the improvement of LID measures on hydrology,water pollution,urban waterlogging and so on.It provides a reference for the optimization process of rainwater system of small towns in arid area under LID measures.The main results of this paper are as follows:(1)the author has carried on the literature research,synthetically analyzed the domestic and foreign advanced LID rainwater management measure theory and the outstanding case,took this as the foundation,has deeply studied the residential site Rain Water system design which takes the LID as the design idea.(2)Combined with the climatic characteristics,topography and landforms of Wangtuan Town,the local water supply and drainage networks and sewage treatment plants were replanned and arranged.Water permeable pavement,family water collection measures,rainwater garden,sunken green space,LID tree pool and other suitable local LID rainwater system planning are designed to prolong rainwater residence time and ensure rainwater emptying in detention facilities to enable rainwater resources to be fully utilized.At the same time,the design method of rainwater system for small towns in arid area under LID is discussed.(3)After the completion of the preliminary planning and design of the rainwater system,the author established the SWMM model of Wangtuan Town before development,after urban development and after the addition of LID measures to simulate the hydrology and water quality under different rainfall characteristics..After the comparison,it was found that after the LID added,the maximum flow rates were reduced by 27.3%,26.4%,25.4%,and 21.7%at the return periods of la,3a,5a,and 10a,respectively;the average flow rates decreased by 39.5%,37.5%,34.3%,and 27.5%,respectively.The runoff decreased by 48.6%,43.6%,36.2%,and 31.1%.The decrease in stagnant water was reduced by 51.1%,49.7%,44.3%,and 39.4%,respectively.The removal of pollutants such as TSS,TP,and COD was also reduced.It is very clear that TSS emissions are reduced by 27.9%,26.7%,25.6%,and 20.6%,respectively;TN emissions are reduced by 58.7%,29%,17.9%,and 12.2%,respectively;TP emissions are reduced by 29%,respectively.17%,11.9%,and 10.8%;COD emissions decreased by 33.3%,18.3%,14.8%,and 11.8%,respectively.In addition,the operation of drainage network is simulated by the models of urbanization and LID.It is found that after joining the LID measures,the pipe network can operate normally and meet the design requirements.Finally,the final planning and design scheme is put forward.(4)Through the above research,it is found that the rainwater system planning and design after adding the LID concept has noticeable improvement compared with the traditional methods in reducing peak rainwater,cutting pollution,and reducing emissions.This study has practical application value to solve the problem of drought management and coexistence of rainwater in small cities and towns in arid areas of China.