Freshwater Quality Indicator

Detailed information for 2005

Status:

Inactive

Frequency:

Annual

Record number:

5128

The purpose of this survey is to obtain information on the quality of surface water in Canada on an annual basis. Data are obtained from water quality monitoring programs managed by Environment Canada, provincial departments, or under federal-provincial agreements.

At present, the freshwater quality indicator is presented as a national histogram of three consecutive years worth of results of the water quality index, calculated at individual monitoring sites across the country. The histogram groups values into five categories: poor, marginal, fair, good and excellent.

Data release - October 15, 2007 (All later indicator reports can be found on Environment Canada's site: www.ec.gc.ca/indicateurs-indicators/)

Description

The surface freshwater quality indicator (hereafter "freshwater quality indicator") provides an overall measure of the suitability of water bodies to support aquatic life at selected monitoring sites in Canada. Its objective is to indicate the exposure of aquatic life to long term and gradual changes in water quality rather than episodic events of pollution or natural phenomena.

At present, the freshwater quality indicator is presented as a national histogram of three consecutive years worth of results of the water quality index, calculated at individual monitoring sites across the country. The histogram groups values into five categories: poor, marginal, fair, good and excellent.

The indicator is based on the application of the Water Quality Index, endorsed by the Canadian Council of Ministers of the Environment in 2001. Complete information on this index is available at http://www.ccme.ca.

An index is calculated for each individual monitoring site for a chosen reference period. During the reference period, water samples are collected. Each sample is analyzed for a suite of water quality parameters. Each parameter value is evaluated against a water quality guideline for that parameter. The percentage of parameters and the percentage of samples that fail to meet the guidelines, and the deviation (excursion) from the guideline for those samples that fail to meet the guidelines, are captured in three factors (i.e., scope, frequency, and amplitude of excursions) used to calculate the index. The index yields a number between 0 and 100. A higher number indicates better water quality.

Annual fluctuations in meteorology and hydrology can have a considerable impact on water quality and, consequently, on the resulting index ratings when applied for individual years. Thus, index scores were based on three years of data in order to dampen the impact of natural variability and reflect a more general status of water quality at that location.

Statistical activity

The goal of the Canadian Environmental Sustainability Indicators (CESI) is to provide Canadians with more regular and reliable information on the state of their environment and how it is linked with human activities. Environment Canada, Statistics Canada and Health Canada are working together to develop and communicate these indicators. Reflecting the joint responsibility for environmental management in Canada, this effort has benefited from the co-operation and input of the provinces and territories.

A description of each indicator is available through the following link:

Subjects

  • Environment
  • Environmental quality

Data sources and methodology

Target population

The universe for this survey is fresh surface water in Canada. The target population is composed of monitoring sites where water samples can be drawn regularly for laboratory analysis and where water quality may be adversely affected by human activity.

Instrument design

This methodology does not apply.

Sampling

It is recognized that the current collection of monitoring networks was not designed to be representative of Canada's hydrological network, but to respond to specific federal and provincial monitoring programs needs. The monitoring sites included in this indicator are almost all located in populated areas and other areas for which it is suspected that water quality is affected directly by human activities such as agriculture, dams, and industries (e.g. pulp and paper and mines). Some sites are also located in areas where human activities affect water quality indirectly, such as areas affected by acid rain deposition. Even so, sites do not comprehensively cover all geographic areas with human activity-related potential water quality issues across Canada.

The data used to calculate the freshwater quality indicator were derived from water samples collected at 340 sites during a three-year period from 2002 to 2004. Data were combined to calculate a single index value for each site.

Generally, the minimum sample number for the three-year reporting period is twelve for rivers and six for lakes. Rivers should be sampled four times a year, the samples being distributed throughout the year to correspond with the spring, summer, fall and winter flow periods. Lake sites may be sampled two times a year if the sampling is done during the spring and fall turnover. Beginning in the 2002-2004 reference period, the minimum number of samples for Northern river sites was reduced to three samples a year, to permit the omission of winter samples.

For the Great Lakes, the indicator was calculated using data collected by Environment Canada's Great Lakes Surveillance Program. Conducted on a two-year rotation, this program took measurements for Lakes Erie and Huron and Georgian Bay in April 2004, and for Lakes Ontario and Superior in April 2005. The indicator for the Great Lakes is also different from the national indicator in that it includes data for lake sediments.

Data sources

Data are extracted from administrative files.

Water quality data used in the calculation of the freshwater quality indicator were obtained from a number of existing water quality monitoring programs across the country. These programs are managed by federal departments, provincial departments, or under federal-provincial agreements. Currently, there is no national network of water quality monitoring sites designed specifically for the purposes of reporting the state of Canada's water quality in a fully representative way at different geographic scales across Canada.

Each program monitors a different array of parameters designed to suit the program's objectives and resource constraints. These monitoring programs track ambient concentrations of substances in the aquatic environment including nutrients (e.g., phosphorus and nitrogen), metals (e.g., mercury), organic compounds (including pesticides and industrial chemicals), and other parameters (e.g., dissolved oxygen, suspended solids and pH). Sampling frequencies also differ among networks according to program needs, resource constraints and accessibility of monitoring sites.

Error detection

Each monitoring program follows standardized methods for sample collection in the field to ensure reliability of measurements. Chemical analyses are undertaken in Canadian laboratories accredited by the Canadian Association for Environmental Analytical Laboratories, ensuring analytical methods are up to standard and proper quality assurance/quality control procedures are in place.

Suspected outliers in the datasets were identified and validated by verifying field forms and books to check for accuracy of data entry, by ensuring that reported units were correct, by consulting stream flow and meteorological records and/or by comparing with the levels of other parameters in the dataset (e.g., turbidity, major ions) that could explain the unusually high or low values of some parameters. Unless proven erroneous, these outliers were left in the dataset.

In most jurisdictions, calculations were done twice after the validation of the data set, and then peer reviewed.

Imputation

Missing data are not replaced with estimated values, with the exception of parameters required to calculate locally-relevant guidelines (e.g., pH, hardness, temperature). If greater than 75% of the values are missing for any parameter than that site must be excluded.

Quality evaluation

Water quality data exist at three levels: individual samples taken at monitoring sites; the combination of individual samples to calculate a Water Quality Index (WQI) value for a particular site; and the aggregated data set of all WQI values from the selected sites across the country.

For a full description of each process please refer to the additional documentation link below.

Freshwater Quality Indicator: Data Sources and Methods

Disclosure control

Statistics Canada is prohibited by law from releasing any information it collects that could identify any person, business, or organization, unless consent has been given by the respondent or as permitted by the Statistics Act. Various confidentiality rules are applied to all data that are released or published to prevent the publication or disclosure of any information deemed confidential. If necessary, data are suppressed to prevent direct or residual disclosure of identifiable data.

Revisions and seasonal adjustment

In most aquatic ecosystems, water quality varies seasonally and annually due to fluctuations in weather such as the timing and amount of precipitation, which affects the hydrological cycle. Thus, three years of monitoring data were combined to calculate water quality index ratings to dampen natural variability.

Data accuracy

Relevance. It is recognized that the current collection of monitoring networks was not designed to be representative of Canada's hydrological network, but to respond to specific federal and provincial needs. Monitoring sites included in this analysis are almost all located in populated areas and other areas for which it is suspected that water quality is affected by human activity. Current water quality monitoring sites do not comprehensively cover all geographic areas with potential water quality issues or problems across Canada. Therefore, the indicator only partially accounts for water quality as per the protection of aquatic life.

Accuracy. Water quality data exist at three levels: individual measurements taken at monitoring sites; the combination of individual measurements to calculate a single summary value for a particular site; and the aggregated data set of all means from selected sites across the country to calculate national and regional trends.

The three levels have their own issues with accuracy. At the first level, each monitoring program follows standardized methods for sample collection in the field to ensure reliability of measurements.

When individual measurements are combined suspected outliers in the datasets are identified and validated. Unless proven erroneous, "outliers" are left in the dataset.

Research has shown that the water quality index is sensitive to the parameters selected, the number of samples and the guidelines applied to test results.

Finally, monitoring sites are frequently located where there are known or suspected problems in water quality and may therefore bias the results of the aggregated indicator.

Timeliness. Site data for the 2002-2004 reference period have been assembled and are available for the 2006 report.

Accessibility. Individual site data are not available. Aggregate data are available as a national histogram that shows the number of sites falling within certain ranges.

Interpretability. Summary results from the assembly of data are available in Canadian Environmental Sustainability Indicators, 2006. Data manipulations and statistical analysis are included in the Freshwater Quality Indicator: Data Sources and Methods, 2006, which describes the data, the methods and the limitations of both for users. Further documentation is available as the Technical Guidance Document provided to scientist compiling the field data.

Coherence. Type and number of parameters and samples included in the indicator calculations vary among the water quality monitoring sites and/or jurisdictions. This flexibility allows for the specific local and regional water quality concerns and objectives of the monitoring programs to be reflected in the index scores. However, these variations in parameter and sample selection make comparability of sites for national aggregation uncertain. In addition, the calculation of the indicator has changed so the results are not comparable to the previous period.

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