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防止洪水泛滥，它们临时储存地表径流，然后以较低的速度释放。雨水池/湿地还发挥着另一个重要作用，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泥沙的增加，艾伯塔河的水质恶化，卡尔加里的暴雨径流是这些污染物进入弓河和埃尔鲍河的主要来源。因此，迫切需要了解现有雨水设施在改善雨水质量方面的表现，以及如何改进未来的设计和优化其运行。然而，雨水池/湿地的性能因当地条件(例如季节和气候、地质和土壤条件、土地使用和排水特征)、暴雨特征和由此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)而差异很大。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物质负荷，并调查控制其在池塘/湿地内的迁移、沉积和循环的过程。为满足这一需要，我们提议实施一个为期5年的项目，主要目标如下：(A)利用流域模型(如SWMM)调查进入卡尔加里雨水设施的沉积物和营养物质负荷；(B)在两年内监测四个现有池塘和湿地的悬浮泥沙输送和营养循环；(C)利用三维水动力-水质模型调查支配雨水池悬浮泥沙输送和营养循环的物理和生物地球化学过程；(D)根据现场监测数据和计算机模拟，制定改进的设计和运行准则。该项目有一个强大的HQP培训部分，包括五名研究生、两名暑期学生和两名博士后研究员。

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.