Assessing risks of eutrophication by urban stormwater runoff under climate change

在整个加拿大，气候变化正在增加城市洪水的频率和强度。反过来，传统的雨水管理（SWM）系统正在向接收水体提供越来越多的城市营养物质峰值负荷。在淡水水生生态系统中，营养物质的过度富集刺激富营养化和藻华的发生。在城市化和气候变化加剧的情况下，受损水生生态系统的恢复成本可能会变得令人望而却步。因此，应根据下游生态风险来设计和改造SWM系统，以尽量减少未来与营养有关的影响。然而，由于缺乏对营养物质沿城市流动路径的命运和运输的预测性理解，目前还没有评估气候变化下城市雨水营养物质输入对接收水的脆弱性的框架。由于认识到需要采取气候适应策略以最大限度地减少城市生态影响，建议的研究将侧重于定量了解城市SWM系统内的营养循环，并开发下游生态系统的风险评估框架。该框架将能够为考虑气候变化下水质目标的SWM设计提供信息。为了实现这一目标，我们将结合实验室实验、实地采样和城市生态水文建模，由学生和博士后进行。这项研究符合NSERC的研究主题“水：健康、能源、安全”，有助于“确保安全的社区水系统”。由于该研究将提高对SWM决策与生态系统影响之间联系的理解，因此对参与流域管理计划、SWM指南和环境法规制定和实施的利益相关者非常重要。这些利益相关者包括但不限于安大略省环境和气候变化部、保护当局和市政当局，它们都是我们的合作伙伴。为城市SWM系统设定积极的营养减少目标将为加拿大节省数十亿美元的未来恢复成本。

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.