SWMM Simulation Of The Combination System Of LID Measures And Stormwater Detention Tanks

Dianchi Lake lies in the southwest of Kunming.Its environment condition is of great importance to Kunmming and the whole Yunnan Provence.In the late 80 s of 20 th century,due to the rapid expansion of social economy,the eco-system of Dianchi has been seriously damaged and remains a disturbing condition till today.At the same tiem,60% of Kunming's annual precipitation centers on summer,which causes heavy flooding in urban area.Both the urban water-logging and water pollution are important problems that should be settled.In order to achieve the goal of 50% annual rainfall interception,a SWMM model is established using data from the area between Luolong River and Xinkai River,witch is 750.5 ha.The separate drainage system is adjusted and improved.Two different improving plane are considered:a)Adding stormwater detention tanks only b)Adding detenion tanks and LID Measures.The detention tanks only system is consisted of a main interception pipe alongside a river and a rainwater drainage system carrying runoff to the interception pipe.Four detention tanks are connecting to the main pipe,with the volume of 5000 m3,4500 m3,4500 m3,4000 m3 respectively.Two kinds of LID measures are considered in the combination system:bioretention cells and permeable pavement.Bioretention cells take 1.5% of the total area,while permeable pavement takes 2.5%?There is no difference between two systems,except the LID measures.Compared to tanks only system,the combination system makes a significant improvement on runoff control,pollution interception and tank volume reduction.Return period valued 0.5,1 and 2 years are considered.In combination system,peak runoff is decreased by 41.75%(0.5a),28.19%(1a)and 18.6%(2a).Total runoff is decreased by 33.48%?26.18% and 20.6%.No obvious delay is detected of peak runoff.LID measures have remarkable influence on pollution interception.In combination system,LID measures intercept 76.40%,76.32%,63,40% remaining pollution respectively.And the interception effectiveness for SS is range from 36.38% to 45.56%,while it is 16.81%~ 26.63% under tanks only condition.Adding LID measures makes a smoother inflow curve of detention tanks.It also saves a lot of detention tank volume.Under 0.5 year of return period,tank volume can be decreased by 44.00%~60.34%.Under 1 year of return period,tank volume can be decreased by 36.00%~49.09%.Under 2 years of return period,tank volume can be decreased by 28.21%~32.56%.