Adaptive management of green stormwater infrastructure to reduce greenhouse gas emissions from urban watersheds

在世界范围内，雨水管理(SWM)系统正在扩大和改造，以应对城市化带来的负面影响，包括洪水增加、河流退化和接收水生态系统的富营养化。在加拿大，雨水池(SWP)是新开发项目的标准SWM技术，尽管其他绿色技术，特别是生物保育系统(BRSS)正越来越多地被使用。然而，这些技术是否也支持积极的气候效益仍然存在争议。例如，温室气体(GHGs)、二氧化碳、甲烷和一氧化二氮的重要来源已被证明是可再生水和可再生能源。然而，它们也固定了碳(C)，减少了磷(P)等营养物质的地表径流，因此改变了营养限制模式、营养条件和沿城市水系和接受水体的温室气体交换。因此，必须在分水岭尺度上评估它们的净影响，以确定SWP和BRSS是加剧还是缓解气候强迫。拟议的项目将通过以下方式解决这一问题：(1)量化控制温室气体交换、C封存以及C和P化学形态和通量变化的SWP和BRSS内的景观尺度驱动因素和过程；(2)将所产生的知识整合到城市流域水文-生物地球化学耦合模型中SWP和BRSS的稳健表示中；以及(3)使用模型模拟来分析城市温室气体排放和养分P输出对绿色SWM基础设施的实施和管理的响应。我们首先将重点放在安大略省南部的城市流域，其中包括SWP和BRSS，我们已经广泛描述了这些流域的水文和生物地球化学特征，从而为在加拿大各地推广模型应用奠定了基础。该项目的市政和工业合作伙伴将利用该项目的成果：(1)开展干预措施，减少现有排污口和保护区的温室气体排放；(2)制定绿色水资源管理战略，最大限度地减少气候缓解效益和其他关键服务(特别是水质保护)之间的权衡。

Worldwide, stormwater management (SWM) systems are being expanded and retrofitted to counter negative impacts of urbanization, including increased flooding, stream degradation, and eutrophication of receiving aquatic ecosystems. In Canada, stormwater ponds (SWPs) are the standard SWM technology for new developments although other green technologies, especially bioretention systems (BRSs), are increasingly used. Whether these technologies also support positive climate benefits remains controversial, however. For instance, SWPs and BRSs have been shown to be significant sources of the greenhouse gases (GHGs) carbon dioxide, methane, and nitrous oxide. However, they also sequester carbon (C) and reduce the surface runoff of nutrients such as phosphorus (P), hence, altering nutrient limitation patterns, trophic conditions, and GHG exchanges along the urban aquatic continuum and in receiving water bodies. To determine if SWPs and BRSs exacerbate or mitigate climate forcing, their net effects must therefore be evaluated at the watershed scale. The proposed project will address this by (1) quantifying the landscape-scale drivers and processes within SWPs and BRSs that control GHG exchanges, C sequestration, and changes in the chemical speciation and fluxes of C and P, (2) integrating the resulting knowledge into robust representations of SWPs and BRSs in coupled hydrology-biogeochemistry models for urban watersheds, and (3) using model simulations to analyze the responses of urban GHG emissions and nutrient P export to the implementation and management of green SWM infrastructure. We will initially focus on urban watersheds in southern Ontario with SWPs and BRSs whose hydrology and biogeochemistry we have already extensively characterized, hence, laying the foundation for expanding the model applications across Canada. The project's municipal and industrial partners will use the project's outcomes to (1) carry out interventions that reduce GHG emissions from existing SWPs and BRSs, and (2) develop green SWM strategies that minimize trade-offs between climate mitigation benefits and other key services, in particular, water quality protection.