Stormwater runoff quantity and quality aspects of winter de-icing operations in urban watersheds

Road salt usage to control snow and ice conditions in cold climates during last few decades has significantly minimized the impacts of winter weather on traffic safety, roadway capacity, travel time and economic costs. However, recently, researchers have found high concentrations of chlorides in surface water and groundwater raising concerns of ecological impacts to sensitive aquatic species and degradation of drinking water supplies. Municipalities and other road maintenance agencies have been proactively trying to find solutions to address the environmental concerns of road salts but poor current understanding of urban snow hydrology and related water quality issues hinder obtaining satisfactory results.;The stream monitoring data indicated that urban streams periodically exceed acute and chronic chloride thresholds affecting some sensitive aquatic organisms. This is more severe in highly urbanized watersheds. Subsurface pathway of chlorides was also found to be significant contributor to the higher chloride loads even during late summer. This research highlights the importance of various chloride sources including road pavements and parking lots under different pathways (surface runoff, interflow and baseflow) in determining spatial and temporal variability in stream chloride mass. The research confirmed that road salt application during last few decades has also elevated the chloride concentration in groundwater. The findings of the research emphasize the importance of snowmelt event type (rain-on-snow, thermal, and salt-induced melt) on urban water quantity and quality during winter season. Better understanding of snowmelt event characteristics assists in identification of opportunities to minimize negative environmental effects of road salts.;This research will contribute for the development and evaluation of novel and innovative best management practices to minimize detrimental environmental effects of road salts by providing means to better represent winter hydrology/water quality processes in a modelling environment.;The intent of this research was to gain a holistic view of the effects of winter weather and road salt application on the urban streams. Temporal and spatial variability in water quality and quantity aspects due to road salts were investigated by analyzing monitoring data collected in Toronto and in Guelph. Based on the monitoring it was attempted to identify and quantify the sources, fate and transport of chlorides in urban watersheds and to represent snowmelt and chloride washoff processes in a modelling environment.