The Black-Severn Watershed
Relative to the other areas in the SGBLS region, the Black-Severn River watershed is sparsely populated (less than 54,000 residents) with few large urban or agricultural areas. The land use tends to be a blend of rural residential and crown land settings where population dramatically increases for the summer months as a result of a vibrant tourism industry and seasonal residents. Within the Black-Severn area there are 9 drinking water systems, serviced by 9 municipal wells and 5 surface water intakes (Figure 2-11), with Orillia being serviced by both wells and a surface intake.
The Black-Severn River watershed lies in the north east portion of the SGBLS region. It contains three upper tier municipalities (Simcoe, Muskoka, and Haliburton), one separated city (Orillia), one single tier municipality (City of Kawartha Lakes) and nine lower tier municipalities (Gravenhurst, Bracebridge, Lake of Bays, Muskoka Lakes, Georgian Bay, Minden, Algonquin Highlands, Severn and Ramara).
Areas of settlement (as defined in the Places to Grow Act, 2005) in the Black-Severn River watershed include portions of Simcoe County, The District Municipality of Muskoka, The City of Kawartha Lakes, The City of Orillia and Haliburton County, as well as the location of First Nation reserves. Within The District Municipality of Muskoka, a number of municipalities are to be the focus of development but of these, only Port Severn falls entirely within this watershed region.
The Black-Severn River watershed has been divided into 8 subwatersheds, or hydrological units, with a combined drainage areas of 2,770 km2. The watershed receives approximately 958.30 mm of precipitation annually.
|Subwatershed||Drainage Area Km2|
|Lake St. John||59.82|
|Upper Talbot River||297.30|
|Upper Black River||392.24|
The Black River is the main tributary of the Severn River and extends from the confluence at Washago northeastward into Haliburton County. The river originates at elevations of 366 m and 396 m above sea level and drains several small lakes before entering Logan Lake. Here it is joined by Anson Creek before draining out and flowing south, converging with Head River just before it enters Lake St. John. It leaves Lake St. John and flows north to enter the Severn River at Washago. The Severn River flows into Little Lake and then into Georgian Bay via Severn Sound. The Upper Talbot River subwatershed is also included in this SWP area. The Talbot River flows into Lake Simcoe approximately 5 km north of Beaverton.
The Black-Severn River watershed is part of the Trent-Severn Waterway. As such, water levels and flows throughout the Severn River drainage basins, including the Black River watershed, are managed by Parks Canada, which is an Agency of Environment Canada.
Overall, 1,682 km2 of the Black-Severn River watershed is considered natural vegetative cover, or approximately 60% of the total area. The percentage of natural vegetative cover within each subwatershed varies from as low as 22% within the Lake Couchiching subwatershed, to almost 69% in the Severn River subwatershed; the Upper Black River has the highest coverage at 84%. Wetlands occupy approximately 14% of the Black-Severn River watershed.
Woodland cover percentage is lowest in the Lake St. John subwatershed (45%) and highest in the Upper Black River subwatershed with approximately 98%. Woodlands reduce the speed of overland water flow and erosion, increase evapotranspiration, intercept rainfall, and increase water infiltration to shallow groundwater areas.
The Black River watershed is located within four regional-scale physiographic regions:
- Number 11 Strip, characterized by deposits of clays, silts and fine- to medium-grained sands that occupy hollows and depressions within the bedrock of the Canadian Shield.
- Carden Plain, which is a limestone plain that extends from the Kawartha Lakes to Lake Couchiching and typically has silt to silty-sand soils less than 1 meter in depth.
- Simcoe Lowlands, which extends from the Dalrymple area to north of Kahshe Lake and adjacent to the Black River, is characterized by flat, low-lying plains composed of clays, silts and fine- to medium-grained sands.
- Georgian Bay Fringe, which borders Georgian Bay and is characterized by exposed bedrock with little soils.