Research On The Calculation Method Of Urban Daily Rainfall And Rain Utilization

Water shortage is becoming more and more serious with the rapid development of the city.At the same time,the loss of a lot of rain resources and flood peak disasters not only had a significant impact to the city,but also had restricted the sustainable development of city.In order to solve the problem about the difficulties of urban flooding and drainage,make full use of rainwater resources and mitigate water scarcity,people need to effectively collect and recycle rainwater.Taking an example of Liaoning province environmental protection science park office outside drainage network engineering,rainwater utilization system and direct rainwater discharge system were compared in the technical and economic aspects.In the technical aspect,design ideas and the rationality of the scheme were compared,the pipeline design length of rainwater utilization system was shorter than direct rainwater discharge system.In the economic aspect,the project cost of these two systems were calculated by Visionbank budget software.The project cost of rainwater utilization system was 5%higher than direct rainwater discharge system.But the late pipeline maintenance cost and community landscape engineering cost of the rainwater utilization system were lower than direct rainwater discharge system.Under the comprehensive consideration,rainwater utilization system gets more superiority.The project cost of rainwater utilization system was determined by the volume of rainwater utilization facilities,and the volume of rainwater utilization facilities has a direct relationship with the local daily rainfall.So the daily rainfall indirectly affects the project cost of rainwater utilization system.In order to get the exact daily rainfall,the daily rainfall formula deriving and rainwater utilization calculation system was designed by C#language.Data file selection and data input module,test module,daily rainfall formula deriving module,daily rainfall calculation module,infiltration system infiltration drainage volume calculation module,storage system storage tank volume calculation module were designed.In the daily rainfall system five sample selection methods have been designed,which are the annual particularly large series method,the annual maximum series method,the annual oversized series method,the annual extremely maximum series method and the annual subprime large series method.The daily rainfall formula deriving module is core design.Firstly goodness of fit test is used to daily rainfall samples by K-S test method,and than make a parameter estimation on the data samples,which conform exponential distribution and gumbel distribution model.The moments estimation method and the least squares estimation method were designed.With the help of calculation error function of the system,daily rainfall formulas can be compared and the best daily rainfall formula can be selected.Using the best daily rainfall formula to forecast the rainfall,and then the volumes of infiltration system and storage systemthe can be calculated.The daily rainfall formula of Shenyang was calculated by the daily rainfall formula deriving and rainwater utilization calculation system with the daily rainfall data of Shenyang from 1951 to 2012.The data sample selection method,the probability distribution model and the parameter estimation method have a variety of combinations.Under different combinations,20 daily rainfall formulas were calculated.Total relative error,absolute variance and relative variance of these 20 daily rainfall formulas were analysised.With the contrast on error calculation of the above 20 daily rainfall formulas,The five data sample selection methods,the two probability distribution model and the two parameter estimation method all applied to calculate the daily rainfall formula of Shenyang.The data sample selection method of the annual particularly large series method and the annual oversized series method,the probability distribution model of exponential distribution model,the parameter estimation method moment estimation method calculating the error values for the daily rainfall formula of Shenyang are smaller.The best combination of Shenyang was "the annual oversized series method-exponential distribution-moment estimation method",and the relevant formula of D-T was D=62.69+25.71 ×LnT.According to the best daily rainfall formula of Shenyang,the daily rainfall thickness can be calculated,T=1a,D=65.2mm;T=2a,D=80.5mm;T=3a,D=90.9mm;T=5a,D=104.1mm.And the volumes of infiltration system and storage systemthe of T=2a can be calculated.The system has characteristics of simple operation and wide range of application,and the degree of daily rainfall forecast and actual value is good.It effectively shorten the time that the design personnel calculates the volume of rainwater utilization system facilities.