Characterising Urban Pollutant Loads
(2003 – 2010)
Effects of urban runoff on aquatic ecosystems, recreational and other functions of waterways concern most, if not all major urban centres. Addressing the impact of poor stormwater quality involves water and environment managers worldwide, calling for accurate, efficient modelling of pollution sources to understand processes and facilitate affordable treatment.
This study builds on findings that rainfall intensity is crucial in pollution generation in stormwater. Short interval rainfall, runoff and pollutant data were collected from over 250 events at seven catchments in metropolitan Melbourne. Pollutant data showed significant differences to that reported in worldwide literature. For example, levels of Total Suspended Solids (TSS) were around half of what was previously reported. Further to this, uncertainties in pollutant data confirm figures of approximately 30%.
To compare factors behind pollutant generation, the study tested a two parameter model for calculating event loads of total suspended solids, total phosphorus and total nitrogen; rainfall intensity, total rainfall, total flow volume and runoff intensity were tested as explanatory factors. Based on that, a two-parameter model explains 90% of variation in event loads. Verification assessed the model’s ability to predict catchments not used for calibration and its sensitivity to parameters and rainfall time step. The model was also tested for within-event behaviour of pollutants, with less success. Impact of the model input errors (systematic and random) on the model performance was examined. It was found that systematic error in rainfall data is the main factor. The study confirms previous research and provides a simple, easy to calibrate model for immediate use by practitioners.
Francey M. (2010) Characterising Urban Pollutant Loads. Department of Civil Engineering, Monash University. PDF (7.1MB)
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