Assessing risks of eutrophication by urban stormwater runoff under climate change****

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All across Canada, climate change is increasing the frequency and intensity of urban flooding. In turn, conventional StormWater Management (SWM) systems are delivering increased urban peak loadings of nutrients to receiving water bodies. Nutrient over-enrichment stimulates eutrophication and the occurrence of algal blooms in freshwater aquatic ecosystems. Restoration costs of impaired aquatic ecosystems under increased urbanization and climate change may become prohibitive. SWM systems should therefore be designed and retrofitted on the basis of downstream ecological risks to minimize future nutrient-related impacts. However, because of the lack of predictive understanding of the fate and transport of nutrients along urban flowpaths, there is currently no framework for assessing the vulnerabilities of receiving waters to urban stormwater nutrient inputs under climate change. Motivated by the recognition of the need for climate-adaptive strategies to minimize urban ecological impacts, the proposed research will focus on the quantitative understanding of nutrient cycling within urban SWM systems, and develop a risk assessment framework for downstream ecosystems. This framework will be capable of informing SWM designs accounting for water quality targets under climate change. To achieve this goal, we will combine laboratory experiments, field sampling, and urban ecohydrological modeling carried out by students and a postdoctoral fellow. The research fits NSERC's research topic "Water: Health, Energy, Security", contributing to "Ensuring secure community water systems". Because the research will improve the understanding about linkages between SWM decisions and ecosystem impacts, it is important to stake-holders involved in the development and implementation of watershed management plans, SWM guidelines, and environmental regulations. These stakeholders include, but are not limited to, the Ontario Ministry of Environment and Climate Change, conservation authorities, and municipalities, all of which are among our partners. Setting proactive nutrient reduction targets for urban SWM systems will save Canada billions of dollars of future restoration costs.