Data Sources and Methods for the Freshwater Quality Indicator

3.1 Data source

Water quality data for 2007 to 2009 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 U.S. Environmental Protection Agency (U.S. EPA), and provincial and territorial sources. A complete list of water quality guidelines used by jurisdiction can be found in Annex 2.

Drainage regions used in the regional WQIcorrespond to those defined in Statistics Canada’s Standard Drainage Area Classification.^[1]

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

Human activity in the drainage basin of core monitoring stations was characterized based on population density using Statistics Canada’s 2006 Census of Population, mine locations using Natural Resources Canada’s 2006 Census of Mines, point-source agricultural activity locations using Statistics Canada’s 2006 Census of Agriculture and land cover using Natural Resources Canada’s land cover maps.^[3],[4]

3.2  Spatial coverage

The national WQI is calculated using a set of core stations selected to be representative of surface freshwater quality across Canada and the human pressure exerted on it. The 2007-2009 national WQIwas calculated using 173 core stations. Because of data availability issues, 2006-2008 data were used as a proxy of the 2007-2009 data for 24 core sites in Quebec.

The local WQI is reported for the 149 core stations for which 2007-2009 data are available and 161 additional local stations across Canada. Data for 2007-2009 for 24 Quebec core stations are not included due to data availability issues. The number of core stations changes every year due to missing data. For this year’s report, water quality is reported at 173 core stations compared to 176 stations in last year’s report. Core stations are added when they meet data standards and requirements of the WQI.

Core station selection

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

Figure 1. Geographic extent of the 16 drainage regions in the more populated regions of Canada used to report the national freshwater

Water quality was also assessed at monitoring stations, called local stations, not included in the core network for local reporting. Specific information on water quality at individual core and local stations can be found in the CESI interactive map.

3.3  Temporal coverage

The WQI was calculated using a minimum of four samples per year from 2007 to 2009 for southern sites. A minimum of three samples per year is allowed for northern and remote stations because winter access can be difficult. A sensitivity analysis concluded no significant difference existed in the water quality score when the mid-winter sample was excluded.^[6] For lake stations, a minimum of two samples per year is required to be taken during the fall and spring mixing, or four samples per year if taken during other time periods.

Three years of data are used to dampen temporal variability in WQI results caused by annual fluctuations in weather and hydrology.^[7] By using a three-year roll-up, the WQI is more representative of the overall freshwater quality at a station. 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 seven core stations: MB05LES015, MB05LIS007, MB05LIS009, MB05LIS014, MB05LIS016, MB05TGS006 and MB05LGS001. These stations were closely evaluated by local water quality experts and included because the data were consistent with previous years and considered representative of local water quality.

Sample timing and frequency varies among monitoring stations and is set according to the monitoring program objectives. There are up to 60 samples for a given parameter at some stations.

3.4  Data completeness

Data quality assurance and 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 done in Canadian laboratories accredited by the Canadian Association for Laboratory Accreditation or the Canadian Standards Council.

For all stations, additional QA/QC on monitoring datasets and calculations of the water quality score are undertaken by Environment Canada. The QA/QC process ensures the dataset meets minimum data requirements and 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 station information from the monitoring programs are stored in a central WQI dictionary, which facilitates the verification of the number of samples, timing location of monitoring stations and calculations.

3.5  Data timeliness

The WQI was calculated using data from 2007 to 2009, the most recent data available from all monitoring programs. For ten core stations, data from the end of December 2006 or the beginning of January 2010 were used to meet minimum samples number requirements. Data from 2006-08 were used as a proxy for the national, regional and human activity impact WQI for the 24 provincial stations in Quebec because data from 2009 were not available at the time of reporting.