Regional Freshwater Quality in Canadian Rivers

For the 2007 to 2009 period, freshwater quality for the protection of aquatic life was rated fair to excellent at most monitoring stations in Canada’s 16 most populated drainage regions. The Saint John–St. Croix, Newfoundland–Labrador and South Saskatchewan drainage regions had higher numbers of stations rated good or excellent. The St. Lawrence, Great Lakes and Assiniboine–Red drainage regions had the highest numbers of stations with poor and marginal water quality.

Freshwater quality in drainage regions for the 2007 to 2009 period, Canada

Map: Freshwater quality in drainage regions for the 2007 to 2009 period, Canada

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How this indicator was calculated

Note: Freshwater quality was assessed using the Canadian Council of Ministers of the Environment’s Water Quality Index. Data from 2006-2008 were used for 24 Quebec stations because 2009 data were not available. Care must be taken when comparing regions, as different parameters and guidelines are used to assess water quality across provinces and territories.
Source: Data assembled by Environment Canada from federal, provincial, territorial and joint water quality monitoring programs.

A drainage region is an area of land where all the water on it drains into the same lake, river or ocean. Stations within a drainage region are connected by a common water source, a common geography and the rivers that run among them. Canada has five major ocean drainage areas, which can be divided into 25 drainage regions. The drainage regions are large and are generally named for the major river or lake systems in Canada.

Freshwater quality at a station is mostly influenced by the human activity in the drainage region and the upstream water quality. Freshwater quality in the headwaters of a river is generally better than that at the mouth because human activities, such as agriculture, industry and urban development, tend to be sparser in the headwaters and build up as the water moves downstream. Pesticides, fertilizers, chemical pollutants and road salt from land-based activities, as well treated municipal and industrial wastewater, affect freshwater quality at the mouth of the river.

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