Simulation And Prediction Research On Distributed Urban Non-point Source Pollution Of Rainfall-Runoff

Water environment problems from urban non-point source pollution have greatly confined the urban economic and sustainable development of our society. In order to control urban non-point source pollution effectively, and to provide useful help for urban water environment programming, estimation and management, predicting the situation in the future is greatly needed. A distributed urban rainfall-runoff non-point source pollution model is established in this paper. The model is applied to analyze the relationship between rainfall type and urban non-point pollution, and to predict the basic characters of urban non-point source pollution in the future. The main content of this paper is listed as follows:Firstly, according to the characters of the sources and pollutants transferation processes, a distributed urban rainfall-runoff non-point source pollution model is established with current advanced theory. It consists of a runoff yield model, a pollution yield model and a concentration model.Secondly, calibration and validation of parameters are developed in the area of Taohuadao in Wuhan, and satisfactory results are obtained: the relative errors are less than 25% for runoff, the relative errors are less than 12% for suspended solid, and for COD, less than 22%. The results indicate that the calibrated model has a certain degree of precision, and can be used in water quality simulation.Thirdly, the model is applied to simulate and predict the non-point source pollution of rainfall runoff in the region of 10.6km2 to the north of Moshui Lake. The three rainfall courses on June 23rd of 2003 with 100.5mm precipitation , June 4th of 2004 with 81mm precipitation and June 14th of 2004 with 45.7mm precipitation are used for the simulation results analysis.In the same kind of rainfall for every kind of subcatchment, the value of SS and COD, flow apex and climax enduring time,are compared respectively, hi the same kind of rainfall, order of the time of flow apex as the following; industrial area shopping center > residential area > meadows, unit load order of pollutants COD in the subcatchment as the following; residential area > shopping center > industrial area > meadows.First flush pollutants load and total pollutants load are computed in the subcatchment for different kind of rainfall. Results showed that, at the beginning of downfall, the maximum ratio of first flush pollutants load to total pollutants load is 97.29%, which of average rain is 81.71 %, of small rain is 41.38%.