Our Watershed

Interesting Facts

Home of the Algonquin people, explored by Champlain, settled by the French and English, now home to people from all over the world, the Ottawa River watershed is huge, diverse, and virtually unappreciated as a single entity.

Stretches from:

    • Shining Tree in the west to St. Jerome in the east;

    • Westport in the south to Launay in the north;

    • Algonquin to Aiquebelle, and from Temiscaming to Tremblay.

Includes Ishpatina, the highest point in Ontario.

With mining in Kirkland Lake and Rouyn-Noranda; forestry in Elk Lake, Barry's Bay and Maniwaki; agriculture in New Liskeard, Kemptville, Renfrew and Oka.

Comprises the nation's capital, Ottawa, and joins the St. Lawrence in Montreal.

With dozens of dams along its main channels producing billions of watts of hydroelectric capacity, and huge storage reservoirs in its northern headwaters - Baskatong, Cabonga, Dozois, Decelles.

With challenging whitewater rivers: the Madawaska, the Petawawa, the Coulonge, the Noire, the Dumoine, the Gatineau, and the Rouge - not to mention the Ottawa itself.

The 200-km P'tit train du Nord bicycle trail traverses the eastern portion of the watershed from St. Jerome to Mont Laurier, passing by Mont Tremblant. It follows the former rail line whose construction was the vision of Antoine Labelle, who spurred the settlement of the Hautes Laurentides area of Quebec.

With the exception of a federal planning board concerned with regulating the flow of the river and its major tributaries, no agency looks at the watershed in its entirety.

The source of the Ottawa River proper is Lac des Ouatouais, from which it flows over 1100 km to Montreal.

The total flow of the river is measured at the last dam downstream in Carillon. It averages just under 2000 cubic meters per second, with a historic minimum of 301 m3/sec in 1971, and a maximum flow of 8190 m3/sec in 1976 (http://www.ottawariver.ca/carillon.htm). Below the dam the river's flow passes through Lac des Deux Montagnes where it splits into two parts. Just under half flows into the St. Lawrence at Lac St. Louis, upstream of the Port of Montreal, and helps maintain water levels for shipping in the Port, augmenting the average flow volume of nearly 8000 m3/sec in the St. Lawrence. The majority of the Ottawa's flow empties from Lac des Deux Montagnes to the north, and splits again into two channels: Riviere des Prairires and Rivieres des Milles Iles. These pass through Montreal, then they rejoin, and finally discharge into the St. Lawrence downstream from Montreal at Repentigny.

Major tributaries of the Ottawa River include:

Map of the Watershed

The information presented above is from two sources: The National Atlas of Canada and a 1984 public information brochure published by the Ottawa River Regulation Planning Board.

From its source east of the Dozois Reservoir to its confluence with the St Lawrence River, the Ottawa River has a length of more than 1,130 kilometres. For most of its length, it forms the boundary between the provinces of Ontario and Quebec. Its basin has a total area of 146,300 square kilometres, 65 per cent of which is in Quebec and 35 per cent in Ontario.