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Backgrounder: Water Quality in Ontario 2008 Report

Archived Backgrounder

Backgrounder: Water Quality in Ontario 2008 Report

Taking action to protect the Great Lakes and Lake Simcoe, reducing toxics and combating climate change are amongst the Ontario government's top environmental priorities.  In this report, the focus is on phosphorus enrichment, acid rain, toxic substances and climate change since information on these issues is important to addressing the priorities.

Monitoring results show the government's actions to improve water quality are making progress, but there is more to be done, particularly in light of climate change. Specifically, the report notes:

  • levels of PCBs and mercury are decreasing in the Great Lakes
  • phosphorus levels in Lake Simcoe are lower compared to past decades
  • northern lakes are showing signs of recovery from acid rain


Water quality moni¬toring measures the success of investments and efforts by governments, industry and individuals to pro¬tect water quality in Ontario.  The ministry's monitoring programs track the overall condi¬tions in the environment, and provide basic information on the quality of water resources across the province.  Ontarians need this information to understand the state of the environ¬ment, the impacts of their activities and the progress that is being made to protect water resources.  The information gained from monitoring helps to prioritize key issues and choose the geographic areas in which to concentrate, thus helping to ensure effective management of water resources.


Programs initiated in the 1970s have reduced phosphorus levels in the Great Lakes and many streams and inland lakes.  This work continues in the Lake Simcoe watershed with the passage of the Lake Simcoe Protection Act in 2008.  Reducing the amount of phosphorus entering Lake Simcoe to approximately 44 tonnes per year is a critical part of the government's efforts to improve the health of the lake's ecosystem.  The long-term monitoring described in this report helped to set this target and will track the progress in restoring Lake Simcoe. Long-term monitoring will help us set new phosphorus targets for the Great Lakes, which are becoming more sensitive to phosphorus loadings due to the impacts of invasive species.

Efforts to control emissions of air pollutants that cause acid rain are ongoing. Results from lakes in the Sudbury area show significant improvement in water quality, however, acid rain remains a problem in the Sudbury area and other lakes in northern and central Ontario.  Also, scientists have noticed that acid-neutralizing calcium in watersheds is decreasing.  It is becoming evident that recovery of lakes from acidification is closely linked to climate change.  Ongoing studies are tracking long-term progress toward environmental recovery.  These studies have local, provincial, national and international relevance as they are the basis for agreements that address air pollutants emitted in Ontario and trans-boundary emissions from other provinces and countries.

Although government regulations have achieved reductions in industrial releases of toxic substances, some toxics persist in the environment because of their longevity, their continued use in some products and the difficulty of cleaning up contaminated areas.  Some new materials that have replaced banned substances, or are used for new applications, have been found in increasing concentrations.  On April 7, 2009, the Ontario government introduced legislation to further reduce toxics in the air, land and water. The proposed Toxics Reduction Act sets out a framework for toxics reduction action by facilities. It would require them to track and quantify the toxics they use and create, to develop plans to reduce toxics, and to report to the government.  Monitoring data supports the development of such strategies and helps to measure their effectiveness by tracking levels of toxics in the environment.  Sport fish and sediment monitoring are particularly effective in tracking trends in toxic substances.  

Climate change models predict a range of impacts on Ontario's water resources including lower water levels, warmer water, more extreme weather events, more droughts, flooding and erosion.  Monitoring results indicate that a warming climate is already affecting Ontario's water resources.  For example, the types of algae in northern Ontario lakes are changing in response to warmer air temperature and longer ice-free seasons.  Monitoring climate change impacts leads to the development of adaptation strategies to protect water resources in the face of future changes in climate.