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Close-up on the
St. Lawrence River
- Monitoring the
  State of the
  St. Lawrence River
- Fact sheets
  - Indicators of the State of the St. Lawrence River
  - State of the Great Lakes–St. Lawrence Ecosystem

Visit the archives 1988-2008 - Saint-Laurent Vision 2000

Water Quality

Water Quality in the Great Lakes – St. Lawrence Basin: Contamination by Toxic Substances

Outlook

More stations are needed to be able to pinpoint the different contaminant sources and geographical distribution and thus acquire a better understanding of the water quality in the Great Lakes - St. Lawrence basin. Although the water shows clear signs of contamination by toxic substances, the levels rarely exceed the CCME guidelines for the protection of aquatic life.

The information presented in this fact sheet refers strictly to the contaminants shown in Table 1. Data on other toxic substances in the aquatic environment are limited. However, technological advances are now making it possible to analyse emerging contaminants such as surfactants, steroids, hormones, personal care products, pharmaceutical residues and brominated flame retardants. Several of these substances are associated with endocrine system disruption in aquatic organisms and research is currently under way to assess the levels of these contaminants in the Great Lakes - St. Lawrence basin. The results will provide a more comprehensive water quality assessment though some new contaminants do not have yet aquatic life criteria.

To Learn More

Cossa, D., Pham, T.T., Rondeau, B., Proulx, S., Surette, C., and Quémerais, B. 1998. Bilan massique des contaminants chimiques dans le fleuve Saint-Laurent. Environnement Canada-Région du Québec, Conservation de l’environnement, et Centre Saint-Laurent. Rapport scientifique et technique ST-163, 258 p.

Kuntz, K.W., and Klawunn, P.J. Upstream/Downstream Niagara River Monitoring Program Draft Report 1999/00 & 2000/01. Environment Canada-Ontario Region and Ecosystem Health Division.

Merriman, J. 1997. Water quality in the St. Lawrence River at Wolfe Island. Environment Canada-Ontario Region and Ecosystem Health Division. Report No. EHD 97-01/I, 17p.

Merriman, J. 1998. Trace organic contaminants in the St. Lawrence River at Wolfe Island. Environment Canada-Ontario Region and Ecosystem Health Division. Report No. EHD 98-02/I, 32 p.

Merriman, J., and Kuntz, K.W. Upstream/Downstream Niagara River Monitoring Program Final Report 1997/98 & 1998/99. Environment Canada-Ontario Region and Ecosystem Health Division.

Pham, T.T., Rondeau, B., Sabik, H., Proulx, S., and Cossa, D. 2000. Lake Ontario : the predominant source of atrazine herbicides in the St. Lawrence River. Can. J. Fish. Aquat. Sci. 57:78-85.

Quémerais, B., Cossa, D., Rondeau, B., Pham, T.T., Gagnon, P., and Fortin, B. 1999. Sources and fluxes of mercury in the St. Lawrence River. Environ. Sci.Technol. 33:840-849.

Rondeau, B. 2002. La qualité de l’eau du secteur fluvial-La contamination par les toxiques. Environnement Canada-Région du Québec, Conservation de l’environnement, et Centre Saint-Laurent. Fiche d’information de la collection Suivi de l’état du Saint-Laurent.

Rondeau, B ., Cossa, D., Gagnon, P., and Bilodeau, L . 2000. Budget and sources of suspended sediment transported in the St. Lawrence River. Hydrological Processes 14:21-36.

Williams, D.J., Neilson, M.A., Merriman, J, L’Italien, S., Painter, S., Kuntz, K., and El-Shaarawi, A.H. 2000. The Niagara River Upstream/Downstream Program 1986/87-1996/97, Concentrations, Loads, Trends. Environment Canada-Ontario Region and Ecosystem Health Division. Report No. EHD/ECB-OR/00–01/l.

Prepared by

Bernard Rondeau
St. Lawrence Centre
Environment Canada

Paul Klawunn
Environmental Conservation Branch (Ontario)
Environment Canada

The Water Quality Index

The Water Quality Index (WQI), like the UV index or the Air Quality Index, is a means of summarizing large amounts of water quality data. Calculating an index serves above all to simplify information in order to make it accessible to decision makers and the public. It also allows water quality data to be compiled and communicated at a national level in a consistent manner. This index takes into consideration many water quality variables and compares them to water quality guidelines or objectives, in order to subsequently rank them (excellent, good, average or poor). The index can be calculated on the basis of criteria adapted to different water uses (drinking water, recreation or, in the present case, aquatic life). Calculation of the WQI is based on three attributes of water quality:

• the number of water quality variables that do not meet objectives;

• the number of individual measurements that do not meet objectives; and

• the amount by which the measurements depart from these objectives.

While it does not replace a detailed data analysis, the purpose of the WQI is to provide a broad overview of environmental performance.

The use of the WQI requires certain precautions. Thus, index comparisons should only be made when the same sets of guidelines are being applied and when the same sets of variables are used. The variables being considered should also be relevant to the water body being tested so the calculated index reflects the condition of this water body.

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