Friday, April 18, 2008

Lower Don Wetlands

The spring is a good time to take stock of our wetlands. What with snow melt and spring rains, there is plenty of water to go around. Some of the wetlands only have water in the spring whereas others keep water all year round. Here's a quick overview of what the Lower Don has to offer in the way of wetlands.

Chester Springs Marsh

Chester Springs Marsh was the first major wetland restoration project of the Task Force to Bring Back the Don in 1996. Entirely dependent on the river for its water, it does dry up during the summer unless there is a big flood. The initial excavation inadvertently exposed an old landfill site beneath which revealed flotsam from a previous generation. The prospect of finding bits of old pottery has attracted people who dig holres here and there looking for items for sale in flea markets. These holes have altered the drainage of the marsh so that water no longer stays around as long as it did when the marsh was first created.

Riverdale Farm Ponds

The granddaddy of the lower Don wetlands, this has been around since the Riverdale Zoo was created in the 19th century. The pond shown here used to have a water fed fountain in the middle of the pond. Ducks and geese swam here fed on a steady diet of bread crumbs fed by zoo visitors. The fountain and the zoo are long since gone but the pond remains. With no steady water input the pond becomes very stagnant in the summer and poor oxygen conditions mean that not much can survive in it. Last year an aerator was installed to pump air into the water. Ongoing studies are monitoring the pond to see if this is improving the pond's living conditions.

Riverdale Park East

This marsh was created about five years ago to capture runoff from the hill and adjacent sports field. It functions fairly well but tends to dry up by mid-July. The city was forced to fence it off because off-leash dogs kept mucking up the marsh and making a mess of the planted bushes and flowers.

Helliwell's Hill

This site just north of the viaduct captures runoff from the DVP. Three small embayments were excavated and they are all full in the spring. However the one pictured usually dries up by mid-June. There may be a small spring that still trickles water into the site because one of the embayments always has a little bit of water in it. However it is totally surrounded by Cattails so it is hard to take a picture of it. The surrounding trees and bushes have done well - some of them are in excess of 10m high.

Binscarth Swamp

Located in a tiny ravine southwest of the Brick Works, this low-lying swamp used to flood a nearby bike path every spring. Fed by a small creek it swells to three times its summer size covering the ground in about 5 cm of water. Last year the city trucked in more gravel for the path and raised it above the flooding depth and added drainage to a ditch beside Bayview Ave. The path now stays dry. During the summer the marsh shrinks down but does retain water year-round.

Don Valley Brick Works

The Brick Works ponds (there are two more in addition to the one pictured) are an outstanding example of a quarry restoration. The former quarry pit was 40m deep in this location. It was all filled in and the ponds were added on top. Today, diverted water from nearby Mud Creek provides a constant flow of water for the ponds and provides and wide array of habitat for a host of wetland plants and creatures.

Beechwood Wetland

One of the newest wetlands, this place is just north of Pottery Road. An old swale was cleared of weeds, expanded and restored with native trees and shrubs. The swale retains water year-round but does shrink in size by late summer. The portion depicted in the picture was mostly dry by August last summer.

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