Introduction

Grenadier Pond (and other ponds) in High ParkHabitat

Grenadier Pond (and other ponds) in High Park Habitat

A kilometre long and half a kilometre wide, Grenadier Pond offers one of the loveliest vistas in High Park. Although much affected by development onsite and in the surrounding neighbourhood, this large natural pond still provides habitat to a wide assortment of water birds, fish, turtles and other wildlife.

Grenadier Pond in winter. Photo: Bob Yukich

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.

Size and Water Flow

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. It is primarily fed by storm sewers and runoff 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 from a pond to the west of Ellis Avenue (West Pond) also flows into Grenadier Pond approximately 30 m to the north of the southwest corner of the pond.

Historically Grenadier Pond was connected directly to Lake Ontario during occasional breaks in the bordering sandbar. The water of Grenadier Pond now drains through a surface outlet at the southwest corner of Grenadier Pond and then through a sewer into the Humber River before finally reaching Lake Ontario. The weir installed (after 1853) at this outlet to regulate water levels in Grenadier Pond was modified in 1996 so that water levels could be lowered seasonally to mimic natural fluctuations. However, regular adjustment of this weir has not been consistently maintained.

Grenadier Pond. Photo: Barbi Lazarus

History of Grenadier Pond

A historic plan of the area from 1864 shows Grenadier Pond separated from Lake Ontario by only a sandbar and the ‘Lake Road’.  The southern edge of the pond was marshland that extended east to connect with today’s Lower Duck Pond. During periods of high water (e.g., spring snow melt), Lake Ontario likely flooded over the sandbar, resulting in occasional flushing of the ponds and elevated water levels (Gartner Lee Ltd. 1995).

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.

The connection between Grenadier Pond and Lake Ontario was cut off in 1853 when the sandbar was widened with fill to accommodate the Grand Trunk Railway, and later widened further by road construction.

In the early 1900s, as the city grew around High Park and the demand for recreation on the pond increased, the marshlands shrank. 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, removing a large section of marsh that once rimmed the pond's southern shore. In the 1950s and 60s close to half of the pond's shoreline was dug up and replaced with turf grass stretching to a solid concrete edge to further increase recreational land.

Impacts on Nature

In the 1880s Grenadier Pond was encircled by rich wetlands that provided an important stopover for many species of migrating birds. The shoreline consisted of cattails, sweet flag, grasses and shrubs. The south end of the pond was a sedge wetland that provided spawning ground and habitat for painted turtles, pike, salmon and largemouth bass.

When the marshy shoreline was removed, the pike population dramatically declined, as did the number of migratory birds. Water quality also suffered, largely because of storm-sewer runoff, contaminated with fertilizers and road salt, flowing into the pond from the surrounding neighborhoods. This, combined with prolific droppings of Canada Geese and decaying sediments, overloaded the water with nutrients, causing an imbalance in the pond's ecosystem.

Growing awareness of the importance of preserving natural areas has sparked a number of restoration efforts aimed at rehabilitating Grenadier Pond (see below).

Views of Grenadier Pond. Photo: David Stoneleigh
Views of Grenadier Pond. Photo: David Stoneleigh

Rehabilitation

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. Removal of most of the concrete curbs and 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).

Great Egret, once a rare southern visitor, is now a regular sight at High Park's ponds. Photo: Tony Pus

The Ellis Ave./Grenadier Pond stormwater facilities were constructed in 2006, following an Environmental Assessment study. This included the construction of a wetland at the southwest corner of Grenadier Pond, with a forebay that can be dredged as needed, and installation of oil separation devices on adjacent roads. The target was 75-80% reduction in suspended solids, as well as the heavy metals and bacteria associated with the solids. The changes were 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.

Great Blue Heron. Photot: Pat Parent

Other Ponds

Although Grenadier Pond is by far the biggest and best known of High Park's ponds, there are several ponds to explore.


Lower Duck Pond. Photo: Barbi Lazarus

The Lower and Upper Duck Ponds are located in the southeast corner of the Park.


There are three less-frequented stormwater ponds in the park: Howard, Ridout and Wendigo Ponds. Howard and Ridout Ponds are at the north end of Spring Creek and can be enjoyed while on the Spring Creek trails. (Spring Creek trail itself surfaces over the historic Laurentian River, seeping through the substrate deep underneath.)


Howard Pond. Photo: Karen Yukich

Wendigo Pond. Photo: Karen Yukich

Wendigo Pond can be found on the west ravine nature trails at the north end of Grenadier Pond.


Black-crowned Night-Heron. Photo: Richard Sigesmund

Stormwater ponds are used to trap sediment from rainfall run-off. These ponds also provide habitat for wetland species, including wood duck which have successfully bred at both the Howard/Ridout Ponds and the Duck Ponds. Black-crowned Night-Herons can be seen hunting or resting in nearby trees.

Last modified: November 12, 2019

Sources

  1. High Park Woodland and Savannah Management Plan, City of Toronto, 2002. PDF (2 Mb).
  2. High Park: Restoring a Jewel of Toronto’s Park System (PDF), Kidd, Christensen and McEwen, Forestry, Parks and Recreation Division, City of Toronto, 2000. Revised and updated January 2008.
  3. ANSI Report - A Botanical Inventory and Evaluation of the High Park Woodlands, S. Varga, 1989. PDF (1Mb)
  4. High Park News, Fall 2006, Natural Environment Committee Update, Karen Yukich
  5. Grenadier Pond, A Self-Guided Walk through the Past (printed brochure)
  6. Proposals for the Rehabilitation of Grenadier Pond et al, Gartner Lee, 1995. PDF (14 Mb).
  7. 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).

See also

News & Sightings

Ecology

History

Birds

Mammals

Herps

Fish

Insects

Trees + Shrubs

Wildflowers

Grasses

Wetland Plants

Invasive Plants

Research

Restoration

Volunteer

Maps