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Canadian WQG


The National Guidelines and Standards Office of the Environmental Quality Branch of Environment Canada provides nationally approved, science-based guidelines for water quality. The Canadian Water Quality Guidelines (CWQG) are developed to provide basic scientific information about water quality parameters and ecologically relevant toxicological threshold values for Canadian species to protect specific water uses. In deriving Canadian water quality guidelines for aquatic life, all components of the aquatic ecosystem (e.g., algae, macrophytes, invertebrates, fish) are considered if the data are available. The goal is to protect all life stages during an indefinite exposure to water. The guidelines provide a numeric value or narrative statement outlining the recommended guideline for over 100 substances, which, if exceeded, may impair the health of Canadian ecosystems and their beneficial uses. In 1999, the Canadian Council of Ministers of the Environment released Canadian Environmental Quality Guidelines (CCME 1999) which included all media (i.e., water, soil air, sediment, and tissue).


The CWQGs are derived from the available literature on the effects of the substance or physical property (e.g., temperature) on various species for the protection of the appropriate use (e.g., aquatic life). Guidelines should not be regarded as a blanket value for national water quality; guidelines may need to be modified on a site-specific basis to account for local conditions. For most water quality variables, a single maximum value, which is not to be exceeded, is recommended as a Canadian water quality guideline. This maximum value is based on a long_term no_effect concentration. Unless otherwise specified, a guideline value refers to the total concentration in an unfiltered sample. When available, the lowest_observable_effects level (LOEL) from a chronic exposure study on the most sensitive native Canadian species is multiplied by a safety factor of 0.1 to arrive at the final guideline concentration. Alternatively, the lowest LC50 or EC50 from an acute exposure study is multiplied by an acute/chronic ratio or the appropriate application factor (i.e., 0.05 for nonpersistent variables; 0.01 for persistent variables) to determine the final guideline concentration.




Aluminum is dependent on pH, Ca2+, and DOC:


0.005 mg/L if pH < 6.5, Ca < 4 mg/L, DOC < 2 mg/L, or


0.1 mg/L if pH >=6.5, Ca >=4 mg/L, DOC >=2 mg/L


I did not enter a value for aluminum




Ammonia is pH dependent:


1.37 mg/L at pH 8.0 and temp 10 C, or


2.2 mg/L at pH 6.5 and temp 10 C


I did not enter a value for ammonia




Cadmium is hardness dependent:


Cd value = 0.001 * [10 ^{0.86 log(hardness)-3.2}]


Formula was for ug/L, so I multiplied by 0.001 to get it to mg/L.




Copper is hardness dependent:


0.002 mg/L at hardness 0-120 mg/L CaCO3


0.003 mg/L at hardness 120-180 mg/L


0.004 mg/L at hardness >180


entered 0.002 as default




Lead is hardness dependent:


0.001 mg/L at hardness from 0-60 mg/L CaCO3


0.002 from 60-120


0.004 from 120-180


0.007 at hardness >180


entered 0.002 as default




Nickel is hardness dependent:


0.025 mg/L at hardness from 0-60 mg/L CaCO3


0.065 from 60-120


0.11 from 120-180


0.15 at hardness >180


entered 0.065 as default




Obtained from Environment Canada’s Canadian Environmental Quality Guidelines web page at