Sediment and nutrient transport and fate in stormwater wet ponds and constructed wetlands

在城市地区，雨水池和人工湿地通常被用来临时储存地表径流，然后以减慢的速度释放出来，以防止洪水泛滥。雨水池/湿地还有另一个重要作用，通过去除沉积物和营养物质等污染物来改善水质。近年来，由于营养水平和悬浮沉积物的增加，阿尔伯塔河的水质已经恶化，而在卡尔加里，雨水径流是这些污染物进入弓和肘部河的主要来源。因此，我们迫切需要了解现有雨水设施在改善雨水水质方面的表现，以及如何改进未来的设计和优化其运作。然而，雨水塘/湿地的性能因当地条件（例如季节和气候、地质和土壤条件、土地用途和排水特征）、风暴特征和产生的水文条件，以及每个设施的设计（例如物理尺寸、流入/流出设计、植物和植被）而有很大差异。因此，需要进行一项全面的研究，以量化池塘/湿地的沉积物和营养负荷，并调查控制它们在池塘/湿地内的运输、沉积和循环的过程。为了满足这一需求，我们提出了一个为期5年的项目，其主要目标如下：(a)使用流域模型（例如SWMM）来调查进入卡尔加里雨水设施的沉积物和养分负荷；(b)监测四个现有池塘和湿地的悬浮沉积物运输和养分循环，为期两年；(c)利用三维水动力-水质模型调查支配雨水池中悬浮沉积物运输和营养循环的物理和生物地球化学过程；(d)根据实地监测数据和计算机模型拟订改进的设计和操作准则。本项目有较强的HQP培训组成，包括5名研究生、2名暑期学生和2名博士后。

In urban areas stormwater ponds and constructed wetlands are commonly used to prevent flooding by temporarily storing surface runoff and then releasing it at a decreased rate. Stormwater ponds/wetlands also have another important role, improving water quality by removing pollutants such as sediment and nutrients. Water quality in Alberta Rivers has deteriorated in recent years due to increases in nutrient levels and suspended sediments and in Calgary stormwater runoff is a major source of these pollutants to the Bow and Elbow rivers. As a result there is an urgent need to understand how existing stormwater facilities perform in improving stormwater quality, and how to improve future designs and optimize their operations. However, the performance of stormwater ponds/wetlands varies greatly as a function of local conditions (e.g., season and climate, geological and soil conditions, land use and drainage characteristics), storm characteristics and the resulting hydrological conditions, and the design of each facility (e.g. physical dimensions, inflow/outflow design, plants and vegetation). A comprehensive research study is therefore needed to quantify the sediment and nutrient loadings to ponds/wetlands and to investigate the processes that govern their transport, deposition and cycling within the ponds/wetlands. To address this need we are proposing a 5-year project with the following major objectives: (a) Use a watershed model (e.g. SWMM) to investigate the sediment and nutrient loads entering Calgary's stormwater facilities; (b) Monitor suspended sediment transport and nutrient cycles in four existing ponds and wetlands for two years; (c) Investigate the physical and biogeochemical processes that govern suspended sediment transport and nutrient cycles in stormwater ponds using a three-dimensional hydrodynamic-water quality model (EFDC); (d) Develop improved design and operation guidelines based on the field monitoring data and computer modelling. This project has a strong HQP training component including five graduate students, two summer students and two post-doctoral fellows.