Evaluation of City of Regina Stormwater Retention and Treatment Pond Performance

Abstract

Municipal storm water retention ponds are required to protect property, reduce negative water quality characteristics and impacts of first flush materials on receiving waters, and mitigate against peak flow challenges for treatment systems and receiving waters under high precipitation or spring flow conditions. To that end, research was completed to review the current operating performance and identify potential concerns with water quality outflows from several of the City of Regina municipal ponds. Additionally, optimization and maintenance suggestions are made to improve performance, where appropriate. The research focuses on retention ponds that are designed to serve as constructed wetlands, as these tend to be relatively new to Saskatchewan and potentially challenging under the climatic conditions presented. The results indicate that the constructed wetlands are strongly influenced seasonally, with concentrations of dissolved oxygen and nutrients fluctuating with air temperature, winds, and precipitation events. All constructed wetlands, at some point in the monitoring program, exceeded water quality thresholds for the protection of aquatic life or general surface water quality management. The pond most often out of compliance was North Windsor, with Windsor also experiencing a significant number of compliance issues. The results further show that the majority of ponds are nitrogen-limited, with one exception (North Windsor), suggesting that management schemes to limit nitrogen (or enhance bioavailable phosphorous) will be most effective for minimizing algal growth in the ponds. Maintenance and management programs that include trigger points (performance thresholds) are recommended to avoid aesthetic and health-related concerns.