Monitoring Water Quality in High Park's Grenadier Pond

Conservation in Toronto's High Park / Research in Toronto's High Park

by High Park Nature

Since 2002, volunteers have been regularly monitoring the water quality of Grenadier Pond through the Lake Partner Program.

Improving the Water Quality of Grenadier Pond

Grenadier Pond is a eutrophic body water, meaning that it is rich in nutrients such as phosphorus and nitrogen. Unfortunately, nutrient-rich waters produce algae blooms and have poor water clarity. Grenadier Pond benefits from extensive historic study, giving us a good picture of how the water quality has changed since the mid-1980s.

Sampling in 1986 and over 1992-1994 demonstrated consistently high phosphorus levels (along with other pollutants). This led to the creation of the City’s restoration program. Improving water quality was one of the priorities and we can see positive changes since the program began compared to studies done in the 1990s (see chart below).

Ray B testing water quality. Photo: Katherine Pawling

Phosphorus results to 2019. Source: Ontario.ca, Lake Partners, etc. Chart: D Kaposi

Testing Grenadier Pond's Water Quality

The Lake Partner Program is a province-wide, volunteer-based, water-quality monitoring program operated in partnership with the Ontario Ministry of Environment Conservation and Parks. Volunteers collect total phosphorus samples and make monthly water clarity observations on their lakes. This information will allow the early detection of changes in the nutrient status and/or the water clarity of the lake due to the impacts of shoreline development, climate change and other stresses.

Phosphorus levels are measured by taking water samples to submit to the Ministry of Natural Resources for testing. Water clarity is measured by lowering a Secchi disk into the water and measuring how far down it goes before it is no longer visible.

Results

Results are posted on the Water Quality in Local Lakes website. Search for location "Grenadier Pond".

To learn more about the Lake Partner Program, visit the Federation of Ontario Cottage Owners' website or download FOCA’s Lake Partner Program report (PDF, 43 pages).

Water Quality of Grenadier Pond (2013)

by Leslie Gooding

Nutrient loading in Grenadier Pond was studied early in the 1990s culminating in the 1995 Gartner Lee report.

Key findings:

phosphorus levels in Grenadier Pond are high
three sources were identified: storm sewers, wildfowl defecation especially Canada geese, and pond sediment, representing historical loading
storm sewer loading could be addressed by downspout disconnection and asking upstream homeowners to be careful about fertilizing their lawns and gardens, and geese could be discouraged by planting the shoreline with native plants, but there were no feasible solutions for removing the phosphorus in the sediment except encouraging a healthy population of predator fish. Reducing the phosphorus in the pond was therefore expected to be slow.

Observations:

mid-latitude lakes are bimictic (all the water mixes twice a year), including Grenadier Pond. This mixing has consequences for the oxygen levels below the thermocline (demarcation between top, stirred layer and bottom layer), which in turn affects the phosphorus levels (pond and lake chemistry is complicated). Thus, seasonal variations from low phosphorus in the spring to high levels at the end of the summer are normal and expected.
the phosphorus levels in Grenadier Pond vary seasonally and from year to year but the long-term average has remained the same.

Blue-green Algae at Grenadier Pond, 2021. Photo: Karen Yukich

Blue-Green Algae

Blue-green algae can rapidly increase to form a large mass or "bloom" when conditions are favourable. If you spot blue-green algal blooms, call the:

Spills Action Centre
1-866-MOETIPS (6638477)
TTY: 1-855-889-5775

Sources

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