The Nottawasaga Watershed is shaped like a bowl. The rim, or the highest areas of the watershed, are the Niagara Escarpment (a World Biosphere Reserve) to the west, the Oak Ridges Moraine to the south, and the Oro Moraine to the east. At the bottom of the bowl is the Simcoe Lowlands and “chip” of the bowl is Nottawasaga Bay at Wasaga Beach.
The Nottawasaga River is the main river in the 2900 km2 Nottawasaga Watershed.
It forms west of the Niagara Escarpment in the Dundalk Till Plains in Amaranth and picks up three major rivers (Boyne River, Pine river, and Innisfil Creek) and countless smaller ones before flowing through the internationally significant Minesing Wetlands. Here, the Mad River and Willow Creek discharge into the Nottawasaga River.
The Minesing Wetlands act like a sponge by holding water and releasing it at a slow rate. As rain falls or snow melts upstream of the wetlands, water flows quickly into streams and rivers and eventually into the Nottawasaga River. As the river reaches the Minesing Wetlands, water flows much more slowly. Under high flow conditions, the rivers can flood over their banks, and spread across the landscape.
Flowing out of the Minesing Wetlands, the Nottawasaga River drains into Wasaga Beach and out into Georgian Bay.