Winter Dynamics of Storm Water Management Ponds and Winter Tolerance in Three Aquatic Plant Species

The vast majority of the research into the performance of stormwater management ponds (SWMPs) has been performed in warm regions or during the warmer seasons in temperate regions. It is presumed that SWMPs are inactive in the winter as any potential stormwater is trapped in snow and ice. The main goal of this thesis was to test this presumption and to study the dynamics and performance of three SWMPs during the winter. Remote water level loggers were installed into the three SWMPs and daily grab samples from the influents and effluents were taken and analyzed for total phosphorus (TP), chloride, total suspended solids (TSS) and turbidity. The three SWMPs were receiving a small amount of inflow every day with a few large stormwater generating events throughout the winter due to a combination of snowmelt and rainfall. The influent concentrations of the contaminants and the performances of the SWMPs in reducing contaminants varied widely. Effluent concentrations of TP exceeded the provincial water quality guidelines between 19.5 – 34.3% of the days. Chloride effluent concentrations in all three SWMPs maintained concentrations above the long-term threshold (120 mg·L-1) for the entire study. Based on current guidelines requiring 70% TSS reduction, two of the SWMPs only met that guideline 9.26% and 21.3% of the days. This is likely due to the positive relationship between the influent concentration and contaminant reduction percentage. These findings suggest that current SWMP monitoring guidelines of only one to four annual inspections and solely measuring TSS reduction is insufficient to accurately assess their performance. Increasing sampling, including influent and effluent concentrations and monitoring more contaminants when assessing SWMPs will better help us to understand their performance in order to protect our local freshwater environments. One suspected reason for poorer performance in SWMPs in the winter is due plant dormancy and a reduction in biological activity. The current guidelines for recommended macrophytes for SWMPs in temperate locations do not consider seasonal dormancy. Three macrophyte species, Elodea canadensis, Nasturtium officinale, and Chara sp. were grown in a cold-growth chamber under simulated winter conditions for eight weeks. All three species continued to perform photosynthesis, modifying their environment by increasing the dissolved oxygen of their containers. On average all species increased their fresh mass after four and eight weeks, with E. canadensis having the greatest growth rate, increasing by 14.2% and 78.9%, respectively. E. canadensis also contributed on average the most oxygen per gram of fresh mass (4.26 mg O2·g fresh mass-1), up to 5 and 9 times greater than N. officinale and Chara sp., respectively. These results indicate that near freezing temperatures and a decreased photoperiod do not induce dormancy in N. officinale, E. canadensis or Chara sp., as they were able to continue to grow and modify their environment. Identifying a community of macrophytes that could be planted in SWMPs that remain active year-round could help to improve the annual contaminant removal of SWMPs