Freshwater Quality in Canadian Rivers

For the 2007 to 2009 period, freshwater quality in rivers in populated regions of Canada was rated excellent or good at 71 monitoring stations (41%), fair at 67 stations (39%), marginal at 30 stations (17%) and poor at five stations (3%).

National freshwater quality indicator for 2007 to 2009, Canada

Note: Freshwater quality was assessed at 173 stations throughout Canada’s 16 drainage regions where human activity is most intensive, 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.
Source: Data assembled by Environment Canada from federal, provincial, territorial and joint water quality monitoring programs. For more information, consult the Freshwater quality indicator: data sources and methods document.

Freshwater quality is important to maintain healthy lake and river ecosystems. Fresh water provides essential habitat for aquatic plants and animals, supports many commercial and industrial uses, and is at the heart of many recreational activities. It varies widely across Canada because of the country’s diverse geography and the different ways in which people have developed the land around rivers and lakes. Each freshwater quality monitoring station sits in an area with its own unique geography and set of human pressures.

For the freshwater quality indicator, water quality was measured at monitoring stations selected to be representative of populated regions in Canada. At each station, physical properties of water, such as pH, and levels of chemical substances, such as nutrients and metals, were measured. To evaluate water quality, the measured physical properties and chemical substances were compared to water quality guidelines for the protection of aquatic life. When a water quality guideline is exceeded, the water quality rating is lowered.^[1]

Change in the national freshwater quality indicator through time

Overall, there has been little change in the national freshwater quality indicator between 2003 and 2009. During this period, no change was detected in the freshwater quality indicator rankings for 69 stations, while the ranking has significantly improved for seven stations and declined for four stations.

National freshwater quality indicator change between 2003-05 and 2007-09

Note: Change in the indicator between the 2003-05 and 2007-09 periods was assessed at 80 stations in 13 drainage regions across Canada where historical data were available. For each station, change in the indicator was assessed using a consistent set of guidelines and parameters through time.
Source: Data assembled by Environment Canada from federal, provincial, territorial and joint water quality monitoring programs.

The freshwater quality indicator changes slowly through time. Factors affecting freshwater quality and how it changes include the amount of pollution released directly into water and the amount that reaches water from land and air. Human activities like urban growth, agricultural activities and industrial development change how water moves across the land and can pollute water. Freshwater quality is also affected by natural changes in rain and snowfall that change the amount of water that runs off the land and brings pollutants to rivers, lakes and reservoirs. The decline in water quality can be slowed by planting trees along a river, upgrading a wastewater treatment plant or adopting a series of agricultural beneficial management practices.

Related indicators

• Regional Freshwater Quality in Canadian Rivers
• Local Freshwater Quality in Canada
• Canada’s Freshwater Quality in a Global Context
• Land Use Impacts on Water Quality

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[1] For example, for some areas, elevated levels of naturally-occurring substances, such as minerals found in rocks, nutrients, glacier deposits and soils, lower freshwater quality index ratings. The Water Quality Index continues to be improved. For a discussion of existing limitations please refer to the Data Sources and Methods.