Canada Water Act annual report for 2019 to 2020: chapter 4

4 Water Quality and Quantity Indicators

The Canadian Environmental Sustainability Indicators (CESI) program provides data and information to track Canada's performance on key environmental sustainability issues including climate change and air quality, water quality and availability, and protecting nature. The water quality and water quantity indicators are highlighted in this section.

Water quality in Canadian rivers indicator

The water quality indicator provides an overall measure of the ability of river water to support plants and animals. The indicator is calculated using the water quality index endorsed by the Canadian Council of Ministers of the Environment to summarize the status of surface freshwater quality in Canada. This indicator reflects the extent to which water quality guidelines for the protection of aquatic life are being met at selected river monitoring sites throughout Canada. Water quality at a monitoring station 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.

The water quality in Canadian rivers indicator released in January 2020 is based on data collected from 2002 to 2018 at 193 water monitoring stations across CanadaFootnote 1 , and reflects the diversity of watersheds in the country. The data were assembled from 16 federal, provincial, territorial, and joint water quality monitoring programs. The National Water quality indicator was calculated using a core national network of 174 river sites, selected to be representative of surface freshwater quality across southern Canada where human pressure is most intense (Figure 4a).

For the 2016 to 2018 period, water quality in rivers in Canada was rated fair to excellent at 80% of the monitored sites. More specifically, water quality measured at these river sites across southern Canada was rated as excellent for 9 sites (5%), good for 61 sites (35%), fair for 70 sites (40%), marginal at 30 sites (17%), and poor at 4 sites (2%) (Figure 4a). Water quality tends to be worse where there is agriculture, mining, high population density or a combination of these (mixed pressures) (Figure 4b).

Water Quality Categories

Excellent
Water quality is protected with a virtual absence of threat of impairment; conditions are very close to natural or pristine levels.
Good
Water quality is protected with only a minor degree of threat or impairment; conditions rarely depart from natural or desirable levels.
Fair
Water quality is usually protected but occasionally threathened or imparied; conditions sometimes depart from natural or desirable levels.
Marginal
Water quality is frequently threatened or impaired; conditions often depart from natural or desirable levels.
Poor
Water quality is almost always threatened or impaired; conditions usually depart from natural or desired levels.
Figures 4a and 4b. Water quality in Canadian rivers, 2016 to 2018 period
Figures 4a and 4b. Water quality in Canadian rivers, 2016 to 2018 period
Long description
Number of sites
Land use category Excellent Good Fair Marginal Poor
Agriculture 0 11 15 4 1
Forestry 1 11 4 1 0
Mining 0 4 4 2 0
Populated 0 0 1 3 0
Mixed pressures 3 22 40 20 3
Undeveloped 5 13 6 0 0
Total 9 61 70 30 4
Percentage of sites
Land use category Excellent Good Fair Marginal Poor
Agriculture 0 6 9 2 1
Forestry 1 6 2 1 0
Mining 0 2 2 1 0
Populated 0 0 1 2 0
Mixed pressures 2 13 23 11 2
Undeveloped 3 7 3 0 0
Total 5 35 40 17 2

Note: Water quality was evaluated at 174 sites across southern Canada using the Canadian Council of Ministers of the Environment's water quality index. For more information on land use classification, consult the CESI Water quality indicator’s Data sources and methods.

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, Natural Resources Canada, Environment and Climate Change Canada, Agriculture and Agri-Food Canada, the Government of Alberta and the University of Maryland.

Overall, water quality has not changed at a majority of sites across southern Canada between 2002 and 2018. Out of the 174 sites, there was improvement in water quality at 17% of sites, deterioration at 14%, and no change in water quality at 69% of the sites (Figure 5).

Figure 5. Trends in water quality, Canada, 2002 to 2018
Figure 5. Trends in water quality, Canada, 2002 to 2018
Long description
Trends in water quality, Canada, 2002 to 2018
Change Number of sites Percentage of sites
Improving water quality 29 17
Deteriorating water quality 25 14
No change in water quality 120 69
Total 174 100

Note: The trend in water quality between the first year that data were reported for each site and 2018 was calculated at 174 sites across southern Canada. 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. The trend was calculated at each site using parameters specific to the site. A site may remain in the same water quality category (excellent, good, fair, marginal, or poor) despite having a statistically significant improving or deteriorating trend in its water quality. For more information on the trend, consult the CESI Water quality indicator’s Data sources and methods section.

Source: Data assembled by Environment and Climate Change Canada from federal, provincial and joint water quality monitoring programs.

Water quantity in Canadian rivers indicator

The water quantity in Canada rivers indicator, updated in January 2020, provides a summary of trends in water quantity in rivers across Canada from 2001 to 2017. The general trends illustrated in Figure 6 are as follows.

Figure 6. Water quantity at monitoring stations, Canada, 2001 to 2017
Figure 6. Water quantity at monitoring stations, Canada, 2001 to 2017
Long description
Water quantity at monitoring stations, Canada, 2001 to 2017
Year Total number of stations High quantity (percentage of stations) Normal quantity (percentage of stations) Low quantity (percentage of stations)
2001 1241 5 68 27
2002 1237 5 79 16
2003 1254 2 76 21
2004 1253 9 85 7
2005 1247 22 74 4
2006 1242 11 78 11
2007 1248 12 80 9
2008 1245 10 86 4
2009 1256 8 82 10
2010 1252 20 73 8
2011 1226 26 68 7
2012 1279 17 70 13
2013 1224 26 68 6
2014 1212 31 61 8
2015 1119 23 64 13
2016 1009 31 56 13
2017 766 26 68 6

Note: The water quantity classification for a station is based on a comparison of the most frequently observed flow condition in a given year with typical water quantity at that station between 1981 and 2010. Data from Northern Quebec are missing for 2016 and 2017 and from the Arctic Coast-Islands for 2017 because of delays in getting data into the database. The results for this indicator vary slightly from those in the Regional water quantity in Canadian rivers indicator because of differences in the methods used to calculate the indicators. For more information, please see Data sources and methods.

Source: Environment and Climate Change Canada (2019) National Water Data Archive (HYDAT).

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