Freshwater quality in rivers
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River plants and animals rely on clean water to maintain healthy populations. The quality of water, and the health of rivers, depends on how people develop and use the surrounding land.
- Most people live in southern Canada where water quality in rivers is most often classified as fair to good. This classification means it can maintain healthy river ecosystems.
- Water quality tends to be worse where there are cities, agriculture, mining, or a combination of all three (mixed pressures).
Water quality, Canada, 2013 to 2015 period
The column chart on the left presents water quality ratings for the 2013 to 2015 period for rivers in southern Canada. Water quality was rated as excellent at 4.5% of monitoring sites, good at 38.8%, fair at 37.1%, marginal at 17.4%, and poor at 2.2% of sites of the 178 sites included in the national indicator.
The column chart on the right presents water quality ratings grouped into 4 land use categories: agriculture, mining, mixed pressures and undeveloped. Good and excellent water quality was found more often in undeveloped areas. Poor and marginal water quality was usually found at sites with agriculture, mining, or a mix of agriculture, mines and cities (mixed pressures) around them.
Data for this chart
|Land use category||Poor (number of sites)||Marginal (number of sites)||Fair (number of sites)||Good (number of sites)||Excellent (number of sites)|
|Land use category||Poor (percentage of sites)||Marginal (percentage of sites)||Fair (percentage of sites)||Good (percentage of sites)||Excellent (percentage of sites)|
|Mixed pressuresFootnote [A]||1.7||9.7||12.5||6.8||0|
Note: n/a = not applicable. Percentages may not add up to 100 due to rounding.
Download data file (Excel/CSV; 1.54 KB)
Note: Water quality was evaluated at 178 sites across southern Canada using the Canadian Council of Ministers of the Environment's water quality index. Two sites have not had their land use categorized because they are close to the Canada-United States border or the ocean. They have not been included in the land use indicator.
Source: Data assembled by Environment and Climate Change Canada from federal, provincial and joint water quality monitoring programs. Population, mining and land cover statistics for each site's drainage area were provided by Statistics Canada.
For the 2013 to 2015 period, water quality at 178 monitoring sites in southern Canadian rivers was rated:
- excellent or good at 43.3% of monitoring sites
- fair at 37.1% of sites
- marginal at 17.4% of sites
- poor at 2.2% of sites
By world standards, Canada has abundant, clean freshwater resources. The quality of water in Canada's rivers varies naturally across the country based on the rocks and soil in the area and the climate. For example, water that flows over the rocky landscape of northern Ontario and Quebec is naturally different from water flowing through the deep soils of the Prairies. However, it is how people have developed the land around lakes and rivers that has the largest impact on water quality at each site.
Water quality is generally very good in undeveloped areas where native plants, trees and soils purify the water before it reaches the river. Adding manufacturing and cities to the landscape means hundreds of different chemicals are released into rivers every day. As well, many contaminants make their way into rivers after being released into the air through burning. Pollution from agriculture reaches rivers through run-off across the soil surface. All of these developments change water quality in a river and put pressure on the plants and animals that live there.
Water quality is reported in this indicator by measuring the levels of a number of chemicals and physical properties (parameters) in water. The levels of each parameter are compared to their water quality guideline. Water quality guidelines are thresholds designed to indicate when a chemical may become harmful to plants and animals. The more often a parameter's concentration is above its guidelines, the poorer the rating of water quality in a river will be.
Trends in water quality in Canadian rivers
- Water quality has not changed between 2002 and 2015 at a majority of sites across southern Canada
- Where it has changed, it has improved more often than it has gotten worse
Trends in water quality, Canada, 2002 to 2015
The bar chart summarizes the trend results. It shows water quality at 11% of the sites (20 sites) have improving water quality and 6% (10 sites) have deteriorating water quality. No trend in water quality was found at 83% of sites (148 sites).
Data for this chart
|Change||Number of sites||Percentage of sites|
|Improving water quality||20||11|
|Deteriorating water quality||10||6|
|No change in water quality||148||83|
Download data file (Excel/CSV; 1.15 KB)
Note: The trend in water quality between the first year that data were reported for each site and 2015 was calculated at 178 sites across southern Canada. A uniform set of water quality guidelines and parameters were used through time at each site for the trend analysis. Changes in water quality from the first year of data collected at the site to 2015 are evaluated by dividing the concentration of each water quality parameter at a site by its guideline for each sampling date. These ratios are averaged annually to obtain the deviation ratio at a site. A Mann-Kendall test was used to assess whether there was a statistically-significant increasing or decreasing trend in the annual guideline deviation ratios at a site.
Source: Data assembled by Environment and Climate Change Canada from federal, provincial and joint water quality monitoring programs.
Water quality in a river tends to change slowly.
Natural factors, such as snow and rainfall, affect water quality by washing pollution that builds up on the surface of roads and fields into the river. A dry year can mean better water quality because less pollution is washed into the river. A changing climate that results in longer wet periods may make water quality worse for longer periods of time.
How the landscape is developed also impacts how quickly water quality changes. Altered landscapes, industrial and sewage effluents, and air pollution deposited on the river surface can all affect water quality. Thus, any change in the amount or type of these inputs over time can also change water quality over the long-term.
Water quality in a river can be improved by modernizing wastewater treatment plants and factories, adopting environmental farming practices, or planting vegetation along river banks.
About the indicator
What does the indicator measure
This indicator provides a measure of the ability of river water across Canada to support plants and animals. At each monitoring site, water quality data are compared to water quality guidelines to create a rating for the site. If measured water quality is below the guidelines, it can maintain a healthy ecosystem.
Water quality at a monitoring site is considered excellent when substances in a river are very rarely measured above their guidelines. Conversely, water quality is rated poor when measurements are usually above their guidelines, sometimes by a wide margin.
Why is this indicator important
Clean freshwater is an essential resource. It protects aquatic plant and animal biodiversity. We drink it, use it for, manufacturing, energy production, irrigation, swimming, boating and fishing. Degraded water quality damages the health of all freshwater ecosystems, such as rivers, lakes, reservoirs, wetlands. It can also disrupt fisheries, tourism and agriculture.
This indicator provides information about the state of surface water quality and its change through time, to support water resource management. It is used to provide information about the state and trends in water quality for the Canada Water Act report and Environment and Climate Change Canada's annual departmental performance reports. It is also used to assess progress toward the 2016-2019 Federal Sustainable Development Strategy.
What are the related indicators
The Regional water quality in Canadian rivers indicator provides more analysis of these indicator results at a regional scale.
The Phosphorus levels in the offshore waters of the Great Lakes indicator reports on the state of and trends in phosphorus levels in the open waters of the Canadian Great Lakes.
Pristine lakes and rivers
This indicator supports the measurement of progress towards the following 2016-2019 Federal Sustainable Development Strategy long-term goal: Clean and healthy lakes and rivers support economic prosperity and the well-being of Canadians.
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