Water Quality Guidelines for Aquatic Ecosystem Health

National water quality guidelines provide a consistent basis for assessing water quality conditions for a designated water use – in this case for the protection of freshwater and marine aquatic life and wildlife. In Canada, there are additional water quality guidelines specific to drinking water, recreational use, and agricultural water use. 

Water quality guidelines can be a useful tool in setting water quality objectives (or targets) to ensure that the concentration of various substances within the water, and the other physical and chemical characteristics of that water, do not have an adverse impact on the health of the fish, plants and other organisms that live there. 

DataStream displays national guidelines for the protection of aquatic life that are published by both the Canadian Council of Ministers of the Environment (CCME) and the United States Environmental Protection Agency (US EPA). These guidelines provide recommended concentration levels for various physical, biological and chemical parameters. 

National water quality guidelines are intended to be broadly applicable across the country. However, unique conditions in some places mean that the guidelines may be over- or under-protective in some areas. 

For example, this might occur if there are species in an area that are more sensitive (or less sensitive) than the species that were studied when the guideline was developed. In other cases, natural background levels of a substance may exceed the guideline without any observed effect on locally-adapted species. Additionally, the unique mix of substances and attributes of water at a given location may result in a substance being more toxic (or less toxic) than it was found to be under the range of conditions that were studied in setting the guideline.

In addition to national guidelines, some provinces and territories have developed their own water quality guidelines. We are currently exploring the potential for additional functionality on DataStream that will enable the display of these provincial/territorial guidelines as well. 

Acute guidelines are set based on the effects of short-term, transient exposures (e.g. abnormal discharges and spills) and generally present higher concentration levels. 

Chronic guidelines, in contrast, are based on the effects of continuous, long-term exposure and have lower recommended concentration levels. 

CCME and US EPA guidelines use slightly different approaches in defining and assessing acute vs chronic exposures.  

• CCME Acute: These guidelines are created using data from short-term exposure periods (24-96 hours). The concentration levels specified are not intended to protect against adverse effects, but rather indicate the level where severe effects are likely to be observed.
  
• CCME Chronic: These guidelines identify maximum concentration levels (or ranges for attributes such as pH) that are intended to protect all forms of aquatic life, at all life stages, for indefinite exposure periods (≥7 day for fish and invertebrates, ≥24 hour for aquatic plants and algae). 
  
• US EPA Acute :  These guidelines refer to the highest 1-hour average concentration that should not result in unacceptable effects if it does not occur more than once every three years, on average. 
  
• US EPA Chronic: These guidelines refer to highest 4-day average concentration that should not result in unacceptable effects if it does not occur more than once every three years, on average. 

Freshwater and marine environments have fundamental differences in water chemistry. For this reason separate guidelines are set for these two different water body types. To date, guidelines have not been developed that are specific to the protection of estuarine species.

CCME provides the following definitions for each water body type:

• Freshwater: Total Dissolved Salt Content ≤ 1000 ppm (1 g/L or 1 ppt)
  
• Marine:  Total Dissolved Salt Content > 5000 ppm (5 g/L or 5 ppt)