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Data Sources and Methods for the Freshwater Quality Indicator


3.1 Data source

Water quality data for 2009 to 2011 were obtained from a number of monitoring programs managed by federal and provincial authorities, as well as by federal-provincial agreements, across the country. The complete list can be found in Annex 1.

Freshwater quality guidelines were obtained from the Canadian Council of Ministers of the Environment (CCME) water quality guidelines for the protection of aquatic life, the United States Environmental Protection Agency (U.S. EPA), and provincial and territorial sources. A complete list of water quality guidelines used by each jurisdiction can be found in Annex 2.

Drainage regions used in the regional Freshwater Quality Indicator (WQI) correspond to those defined in Statistics Canada’s Standard Drainage Area Classification.Footnote [1]

The upstream drainage area of core monitoring sites was delineated using Natural Resources Canada’s National Hydro Network.Footnote [2]

Human activity in the drainage basin of core monitoring sites was characterized using population density from Statistics Canada’s 2006 Census of Population, mine locations using Natural Resources Canada’s 2006 Census of Mines, agricultural activity locations using Statistics Canada’s 2006 Census of Agriculture, and land cover using Natural Resources Canada’s land cover maps.Footnote [3],Footnote [4]

3.2 Spatial coverage

The national WQI is calculated using a set of core sites selected to be representative of surface freshwater quality across Canada and the human pressure exerted on it. The 2009-2011 national WQI was calculated using 172 core sites. The number of core sites can change from one year to the next due to missing data.

The local WQI is reported for the 172 core sites for which 2009-2011 data are available and 162 additional local sites across Canada.

Core site selection

Among Canada’s 25 drainage regions, 16 were selected based on population density for the WQI core network (Figure 1). Within the 16 selected drainage regions, core sites were selected to avoid overlapping drainage areas and to ensure sites are independent of one another. The upstream drainage area of monitoring sites was delineated by Statistics Canada using the National Hydro Network.Footnote [5] Where upstream drainage areas of monitoring sites overlap, the most downstream site was retained for the core network, as this site is impacted by the maximum area in the river basin and, to some degree, reflects the cumulative impacts of all upstream stresses. For 14 large rivers, including the Athabasca and North Saskatchewan rivers, core sites were established in the upper, mid and lower portions of the river as well as the most downstream sites on each tributary when available. Additional core sites were established on these rivers, as water travels thousands of kilometres from source to mouth. Water quality changes along the way and cannot be summarized by a unique downstream monitoring site. The final selection of core sites ensures monitoring sites are well distributed among provinces, territories and drainage regions and represent land use in the drainage region.

Figure 1: Geographic extent of the 16 drainage regions selected for the core network

Figure 1: Geographic extent of the 16 drainage regions selected for the core network

Long Description

The map of Canada shows the drainage regions selected for inclusion in the freshwater quality indicator core network. Of Canada’s 25 drainage regions, 16 have been selected for inclusion.

Water quality was also assessed at monitoring sites known as ‘local sites’ that were not included in the core network. Information on water quality at individual core and local sites can be found in the CESI interactive freshwater quality map.

3.3 Temporal coverage

The WQI was calculated using a minimum of four samples per year from 2009 to 2011 for southern sites. A minimum of three samples per year is allowed for northern and remote sites because winter access can be difficult. A sensitivity analysis concluded that no significant difference existed in the water quality score when the mid-winter sample was excluded.Footnote [6] Three years of data are used to dampen temporal variability in WQI results caused by annual fluctuations in weather and hydrology.Footnote [7] By using a three-year roll-up, the WQI is more representative of the overall freshwater quality at a site. It minimizes the effects of events, such as high or low flow, by avoiding one sample driving the WQI score up or down.

Minimum sampling requirements were not met at 10 core sites: 9 in Manitoba and 1 in New Brunswick. The sites are remote, making sampling during the winter months difficult, dangerous and costly. These sites, however, were closely evaluated by local water quality experts, and were included because the data were consistent with previous years and were considered representative of local water quality.

Sample timing and frequency varies among monitoring sites and is set according to the monitoring program objectives. There are up to 131 samples for a given parameter at some sites.

3.4 Data completeness

Data quality assurance/quality control (QA/QC) is performed within each monitoring program providing data for the WQI. Each monitoring program follows standardized methods for sample collection in the field. Chemical analyses are performed in Canadian laboratories accredited by the Canadian Association for Laboratory Accreditation or the Standards Council of Canada.

The data undergo an additional QA/QC process by Environment Canada to ensure the dataset meets minimum data requirements and that standards for calculation are respected. This process leads to removal of parameters due to low sampling frequencies or because detection limits are higher than guidelines used in the calculation. Unusually high or low values in the monitoring datasets are double-checked and confirmed through consultation with the data provider. WQI scores and site information from the monitoring programs are stored in a central WQI dictionary, which facilitates the verification of the number of samples, sample timing and the location of monitoring sites, and calculations.

3.5 Data timeliness

The WQI was calculated using data from 2009 to 2011, the most recent data available from all monitoring programs. For 10 core sites, data from late December 2008 or early January 2012 were used to meet requirements for minimum number of samples.