2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
Dr. Tadros Ghobrial, Dept. of Civil and Environmental Engineering, University of Alberta
Dr. Wenming (William) Zhang, Dept. of Civil and Environmental Engineering, University of Alberta
Dr. David Zhu, University of Alberta
Dr. Mark Loewen, University of Alberta
Mr. Khizar Mahmood, City of Calgary Water Resources
Mr. Bert van Duin, City of Calgary Water Resources
Wet ponds and constructed wetlands are commonly used to control excess runoff in urban areas by temporarily storing surface runoff and then releasing it at a controlled rate. They can be effective in improving water quality by removing sediments, nutrients and pollutants in stormwater runoff. As a result, there is an urgent need to understand the complex physical, chemical and biological processes in stormwater facilities as a function of local conditions (e.g. climate, geological conditions, and drainage characteristics), hydrological conditions, and the design of each facility (e.g. physical dimensions, inflow/outflow design).
A comprehensive 2-year field monitoring program is being undertaken to monitor two wet ponds and two constructed wetlands in Calgary, Alberta. The field data will be used in the development of a watershed model (SWMM) to investigate the suspended sediment and nutrient loads entering the ponds/wetlands and will support the application of the Environmental Fluid Dynamics Code (EFDC) model to investigate the physical and biogeochemical processes that govern suspended sediment transport and nutrient cycles in ponds/wetlands. Both the field monitoring data and computer modelling will be used to improve the design and operation guidelines of stormwater facilities.
The field study included deployment of a meteorological station at each site to monitor air temperature, relative humidity, wind speed, wind direction, rainfall and solar radiation. In the inlet/outlet structures of each facility flowrate, turbidity and water temperature were monitored and water samples were collected during rain storms using autosamplers. In-pond moored instruments were deployed at three locations in each pond/wetland to capture horizontal and vertical variability of water quality parameters. The moored instrumentation measured water temperature, depth, conductivity, dissolved oxygen (DO), turbidity, pH and chlorophyll-a throughout the water column. At the same locations during bi-weekly field trips, higher resolution vertical profiling of the same parameters was conducted and water samples were collected at different depths. Velocity measurements were collected along the main flow-path in two of the stormwater facilities.
This paper will present preliminary results from the first year (2018) of the field monitoring program. The response of the four ponds/wetlands to meteorological forcing (e.g. rainfall, wind and air temperatures) will be examined in detail. The hydraulic performance of the facilities will be investigated by analyzing inflow/outflow hydrographs, water levels and residence times. The occurrence of stratification and its impact on water quality will also be reported.