Study On Intercepting Capability And Operational State Of Interception Trunk (Eastern Section) Of The Dianchi Lake Based On SWMM

In order ot protect the environment of the Dianchi Lake, state and localgovernments have invested a lot of material and human resources for controllingpollution of the Dianchi Lake. During the Ninth Five-Year Guideline, the TenthFive-Year Guideline, and the Eleventh Five-Year Guideline, a series of key govermanceprojects were implemented, and the trunk engineering framework from sourcecontrolling to the end intercepting was established. Among the interception hierarchy,the water analysis, operation and regulation of interception trunk is essential for theentire interception system.In order to predict the changes in carrying capacity of interception tunk afterurbanization, give full play to the intercepting capabilities of interception trunk andwhole system, this article builted a suitable SWMM model of study area. Afterparameter calibration and model validation, different scenario analysis and waterquantity analysis of the interception trunk was done. As a prerequisite for the simulationmodel, selecting representative rainfall events and rainfall sequence screenings isnecessary, through the statistical analysis of the hourly rainfall data for Kunming from1995to2009, the rainfall features with “short duration”,“forward rain peak position”were summarized. The typical rainfall evets were selected and suitable rainfall durationcurves were designed by Chicage Storm Synthesis Method for simulation.According to the simulation results, the following conclusions were summarized:①According to the hourly rainfall data from1995to2009, the interannual rainfallof Kunming are inhomogeneous; The rainfall is mainly concentrated in the May toOctober; The rainfall events are mainly with short duration (1~3h), most of the rainfallevents lasted for2h; According to the typical rainfall events during2009to2013, therainfall events of Kunming are mainly with short duration, single peak(the rain peakposition is in the first quarter of the total duration).②Through simulations under the measured rainfall events and designed rainfallevents, it concludes that the interception trunk can carry the run-off generated by thewhole study area under moderate rain, light rain with16mm total rainfall, and thedesigned rainfall events with design return period of0.5year, and the capacityutilization of the interception trunk can reach90%; There is low-lying nodes in theinterception trunk which will overflow under rainfall events with greater return period(greater than1a), these weak nodes can be considered as the position for settingrainwater storage facilities; Under the rainfall events with the total rainfall of16mm, theratio of the outlet flow of the interception trunk and the designed influent flow ofLuolong river wastewater treatment plant is between8to9.③The regulation and storage capabilities of the gates set at a distance in theinterception trunk is negligible, the gates mainly functioning in flushing.④The size of the outlet pipe diameter has a great influence in the oulet flow of theinterception trunk, enlarging the diameter of the stormwater drain is benefit for sharingthe influent flow of the rain stations and wastewater treatment plant equally.⑤Under the rainfall events with the same rain intensity and different rainfall peakposition, the outlet peakflow of the interception trunk will appear at different time; Forthe rainfall events with considerable total rainfall, the greater of the maximum hourlyrainfall, the outlet peakflow gets greater, and appears ealier.⑥Under the rainfall events with same rainfall intensity, the larger the range ofrainfall enveloped, the outlet peakflow gets greater, and appears ealier.⑦During1995to2009, the ratio of the overflow volume of the whole system andthe total runoff ranges from6.72%to20.59%yearly. When the entire interceptionsystem of the east coast of Tien Lake functioning, the interception trunk can play astrong role to ensure interception during rainy seasons, if the proportion of disposableflow of the interception system in front of trunk is greater than the annual highest ratioof flooding of the whole system.The simulation method and procedure of this article have a certain reference valueand reference for the similar work of other cities.