Urban stormwater forecasting model and drainage optimization based on water environmental capacity

Drainage systems in China are currently being transformed from combined sewer systems into separate sewer systems; newly built areas generally use the latter for sewage and stormwater treatment. Polluted stormwater runoff is discharged directly into rivers through pipelines, thereby deteriorating the water quality of rivers. In this work, an urban stormwater system model was built with Infoworks Integrated Catchment Modeling and validated by measured data. The loads at the pipe outlets during rainstorms were analyzed as well. Stormwater system was transformed by using mathematical models under the conditions of meeting river water quality standards and preventing damage to water environmental capacity. The relative errors of volume and peak runoff of model calibration were from -2.33 to +12.06 % and -13.43 to +8.7 %, respectively. The study indicates that the stormwater system model can be used in scenario analysis, and the stormwater system can accommodate floods over a recurring interval of 10 years. Moreover, stormwater can be directly discharged into water bodies without exceeding the carrying capacity of the water environment with the transformation of the stormwater system.