Twelve Mile Creek

What is a Watershed?

• A watershed is an area of land  drained by a river system. Any land with surface water draining into Twelve Mile Creek is part of the Twelve Mile Creek watershed. This watershed and multiple other river watersheds flow into Lake Ontario, and are part of the Lake Ontario watershed, which is part of an even larger watershed - the Great Lakes Basin watershed which includes all of the Great Lakes and flows into the Atlantic Ocean.

Twelve Mile Creek Watershed

• Flowing in a northward direction the Twelve Mile Creek watershed drains into Lake Ontario at Port Dalhousie.

• The 'upper' portion of the Twelve Mile Creek Watershed is the last spring fed section of coldwater stream remaining in Niagara.

• The headwaters begin in Pelham and Thorold, approximately bounded by Balfour St. to the West, Highway 20 to the south and Highway 406 to the east.

• Water diverted from the Welland canal enters the creek above the Decew power generating station and at this point lower Twelve Mile Creek is no longer considered a coldwater stream.

From Glaciers to Groundwater

• The town of Fonthill is situated on a unique geological feature, a Kame Delta, formed approximately 13000 years ago. Where the edge of a glacier abutted former lake Warren, a channel of glacial runoff deposited gravel and sand into the water. The deposits of gravel and sand piled up, abutting the edge of the glacier and now form the north slope of the Fonthill Kame. Sediment from this meltwater channel spreads out to the southwest and extends towards Fenwick. Reservoirs, or aquifers, now exist where  groundwater moves slowly through the spaces between this loose sediment.

• As the glacier retreated to the north, further glacial till was deposited in its wake. Ultimately drainage shifted to the north, through a pre-existing notch in the Niagara escarpment formed by pre-glacial Erigan Channel. Now known as the Short Hills, this area is characterized by deep gorges and ravines created by drainage over the loose deposits left by the glacier.

• Main branches of Twelve Mile Creek from west to east are Swayze Creek, the Effingham/St.John’s branch, Terrance Creek and the Wetaskiwin branch.

Value of Groundwater

• Groundwater moves slowly under the earth’s surface, stored in the pore spaces between rocks and soil. The level at which layers of material are completely saturated with water is called the water table. 

• Springs occur where the water table intersects with the land surface.

• Groundwater remains near 11 or 12°C throughout the year. 

• The slow movement of water through the soil filters out pollutants and leaves sediment in the ground. Spring water supplies cool, clear water to the watershed. 

• Groundwater resources are recharged by the infiltration of precipitation and meltwater as they soak into the ground.