Surface Water Quality

Monitoring water chemistry, metals and bacteria helps us to understand the impacts of land use on the water quality of the local streams and watercourses that ultimately flow into Lake Ontario.

What Do We Monitor and Why?

Since 2002, TRCA has partnered with the Ontario Ministry of the Environment and Climate Change to monitor surface water quality across the region’s watersheds. Water quality samples are collected monthly at sites unique to TRCA properties as well as some that have been adopted from Ontario’s Provincial Water Quality Monitoring Network. The water quality grab samples are analyzed for a standard suite of water quality parameters, including heavy metals, nutrients and bacteria.

Water temperature loggers are also installed at various restoration sites along the Toronto area waterfront for monitoring purposes.

water quality monitoring

What Are The Data Telling Us?

Current data analyses show that site water quality conditions are directly linked to the scale of urbanization upstream of a monitoring station. Nonpoint sources of contamination from urbanization, such as sediment, nutrients and chemicals, continue to be the largest contributor to poor water quality conditions within TRCA’s jurisdiction. Point sources of contamination, such as discharge from wastewater treatment plants and industries, also contribute to the degradation of water quality in the GTA. Certain contaminants (e.g. total phosphorus) have decreased over the past 20 years while others such as chloride, derived from road salts, show an increasing trend.

Environmental Monitoring surface water quality map 2014


Jan Moryk, Project Manager
Environmental Monitoring & Data Management