Canadian Geographic
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Watershed awareness

Urban watershed issues

Between 1971 and 2001, Canada’s urban population grew by eight million people and urbanization consumed over 15,000 square kilometres of land. The resulting conversion of natural habitat to impermeable surfaces like asphalt and concrete has created unprecedented water and sewer challenges for both municipalities and natural freshwater systems alike.

By 2001, one-third of Canada’s population occupied six very highly urban watersheds, sitting on only 2.9 percent of Canada’s land area. The number of people living in very highly urban watersheds increased by 45 percent between 1981 and 2001. In Ontario alone, over six million people occupy just one watershed. In short, Canada’s urban population and urban land-use practices exert enormous pressure on watersheds, and cities are feeling the effects. In 2004, about one-quarter of responding Canadian municipalities reported water shortages.

As urban populations grow, so does the demand for increased water supply, drainage and waste-water treatment. More waste-water discharge results in decreased oxygen levels in water, eutrophication, bans on fish and shellfish consumption and beach closures. Municipal waste-water effluents — a cocktail of human waste, suspended solids, debris and chemicals from residential, commercial and industrial sources — comprise the largest source of effluent discharge to Canadian waters.

Another concern in urban areas is storm-water runoff, which is typically shunted off impervious surfaces, such as rooftops and roads, straight into storm-water drains, which feed directly into the nearest creek, river or lake. The problem with this is twofold. First, as soon as rainwater hits an urban surface, like a driveway or highway, it becomes polluted with the grime that coats our cities — phosphorus from lawn and garden fertilizers, heavy metals, PCBs and motor oil, to name a few. Then the storm water is discharged untreated into the watershed. Second, as storm water collects in storm-water drains, it gains so much momentum that it can destroy aquatic habitats where it is discharged.


This piece teaches users about storm water runoff and how it can be hazardous to the environment and nearby bodies of water. A series of animated vignettes explain some approaches for minimizing contamination and other issues associated with this run-off.


On the next page:

Northern watershed issues

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Quiz :

Approximately what percentage of Canada's fresh water lies north of 60 degrees latitude?