Analysis on Water Quality Characteristics of Typical Black and Stinking River in Chengdu City by SWMM

In this paper, based on Storm Water Management Model (SWMM) mechanism, referring to the model parameters of domestic and foreign related research achievements, combined with field monitoring data, a non-point source pollution load calculation model is constructed, and the corresponding parameters are calibrated. The pollution load and pollution change process of chemical oxygen demand (CODCr), ammonia nitrogen (NH3-N) and total phosphorus (TP) under different rainfall conditions were analyzed in the investigation area. The model calculated values are in good agreement with the actual measure results. Under different rainfall conditions, the maximum value of pollutants appeared in early and middle rainfall stage, while gradually decreased in latter, with the increase of rainfall, pollution of receiving water becomes greater, and the pollutant concentration shows a downward trend during rainfall process. Measured value of CODCr is higher than the simulated one, both decreased gradually with the rainfall, measured NH3-N concentration in mid-term rainfall increased slightly due to the uninterrupted direct emission of domestic sewage in this area, measured TP concentration in early stage of rainfall declined not obvious, but with the rainfall enhancement, various phosphorus compounds by erosion gradually dissolved finally into the river, partially offset by a dilution effect, as the subsequent rainfall carried over, total phosphorus pollutants continued to decline. While as impervious surface area goes on, both runoff and total pollutants increase.