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Common Birds of High Park Wetlands | Bird Gallery - Wetlands | Common Waterbirds of Grenadier Pond | Fish | Dragonflies & Damselflies | Fluctuating Water Levels | Monitoring Water Quality | Deadwood in the Pond
Grenadier Pond is the largest of several ponds in High Park. Development in the surrounding drainage area has reduced its size from 19 ha in historical times to its present size of 14.2 ha.
Grenadier Pond is one of the areas within High Park that has been designated as an Area of Natural and Scientific Interest (ANSI) by the Ontario Ministry of Natural Resources based on a report by Steve Varga in 1989. According to this report "The wetland communities at Grenadier Pond are noteworthy at the local level for harbouring one of only two remaining lakefront marshes in the City of Toronto, the other being the Humber River Marshes...The remaining wetlands at Grenadier Pond should be protected as a locally significant lakefront marsh which still supports regionally rare wetland species."
Grenadier Pond is primarily fed by storm sewers and run-off from land to the west and east of the pond. To the south, the pond is separated from Lake Ontario by roadways, a railway and Sunnyside Beach. Water flows into a surface outflow at the southwest corner of Grenadier Pond to the Humber River, and then empties into Lake Ontario. Water from a pond to the west of Ellis Avenue (West Pond) also flows into Grenadier Pond approximately 30 m to the north of the outflow.
It is likely that the ponds were at one time separated from Lake Ontario by a sandbar (Wainio et al. 1976). During periods of high water (e.g., spring snow melt), Lake Ontario likely flooded over the bar, resulting in occasional flushing of the ponds and elevated water levels (Gartner Lee Ltd. 1995). After the connection between Grenadier Pond and Lake Ontario was cut off by road and railway construction, an outlet weir was installed (after 1853) to regulate water levels in Grenadier Pond. The weir was subsequently modified in 1996 so that water levels could be lowered seasonally to mimic natural fluctuations.
Mapping sources indicate that the surface catchment area for Grenadier Pond was much larger historically (47.7 ha) than it is today (24.5 ha), and extended as far north as St. Clair Avenue. When the lands surrounding Grenadier Pond were developed, the drainage system was extensively channelized into storm sewers, and much of the runoff from hard surfaces was diverted out of the catchment. These changes have resulted in a substantial drop in the annual volume of water directed to the pond from groundwater contributions. Structurally, the pond has been “renovated” in successive waves of development, particularly on the eastern and western shorelines (Gartner Lee Ltd. 1995). Wainio et al. (1976) describe the land use changes that have occurred around the perimeter of Grenadier Pond since 1947, after which approximately 4.45 ha were filled to accommodate an expansion of the Queensway roadway.
Major efforts to rehabilitate Grenadier Pond began in 1994. These included fish stocking (Largemouth Bass and Northern Pike), water quality surveys, and the propagation of native shoreline plants at the High Park nursery. The restoration of the Grenadier Pond shoreline began in the southeast corner in 1995, and the southwest corner, East Cove and Maple Leaf shoreline in 1996. In 2005 another naturalization project extended the softened edge across the entire south shore of the pond. Shoreline plantings were implemented to enlarge the remnant areas of wetland remaining around the pond and to reduce the impact of waterfowl on the water quality of the pond (nutrient loading).
The Ellis Ave./Grenadier Pond stormwater facilities were constructed in 2006. This included a wetland at the southwest corner of Grenadier Pond, with a forebay that can be dredged as needed, and oil separation devices on adjacent roads. The target is 75-80% reduction in suspended solids, as well as the heavy metals and bacteria that are associated with the solids. The changes are expected to result in cleaner water going into Grenadier Pond, more treatment of water flowing out of Grenadier before it reaches the lake, and reduced risk of flooding to adjacent properties. In 2007 additional restoration along the east shore of Grenadier Pond improved fish habitat through a series of underwater shoals, log cribs and root wads.
Read the Environmental Assessment Study for the Ellis Ave. project.
Compiled by: Karen Yukich
High Park Woodlands & Savannah Management Plan, City of Toronto, 2002 pdf (City of Toronto report, 25 mb)
High Park: The Jewel of Toronto's Park System, City of Toronto, rev. 2008 pdf (City of Toronto brochure, 5 mb)
ANSI Report - A Botanical Inventory and Evaluation of the High Park Woodlands, S. Varga, 1989 pdf
High Park News, Fall 2006, Natural Environment Committee Update, Karen Yukich
Proposals for the Rehabilitation of Grenadier Pond, Wendigo Creek and Associated Wetlands, Gartner Lee Limited, 1995 Part 1,Part 2, Part 3, Part 4, Part 4, Part 5, Part 6, Part 7, Part 8
A few historic documents at the High Park branch of the Toronto Public Library in the local history archives (do not circulate), including:
- An Ecological Study of Grenadier Pond (1976)
- The Comparative Limnology of Grenadier and Catfish Pond (1986).