This study was conducted to evaluate impacts of stormwater ponds in the Municipality of the Town of Richmond Hill on select physical (temperature, dissolved oxygen, and pH) chemical (nutrients) and biological (macroinvertebrate community, macrophyte and experimental Hyalella azteca and Daphnia magna enclosures) aspects of a Rouge River tributary. Over a five-month period five sites along the tributary close to the outfall of the stormwater ponds were sampled to determine if there were any impacts, cumulatively (with increasing number of pond outfalls along the tributary) and locally (above and below an outfall). Physical and nutrient parameters showed no signifiant degradation in water quality, either cumulatively or locally. Macrophytic data showed some decrease in biomass at downstream sites, but no decrease in diversity or species richness. Survivorship in the enclosures containing Hyalella azteca and Daphnia magna showed no significant cumulative change. Analysis of the macroinvertebrate community showed no cumulative or local impact until the farthest downstream site.