Watershed Facts

Name Origin: Derived from the Algonquin term adawe (“to trade”). The name was given to the tribe which controlled the trade of the river. The name was first applied to the river and then to the city. The French form is Outaouais. Formerly known as Kitche-sippi, La Grande Rivière or the Grand River.

Source: Lake Capimitchigama (QC): located 250 km north from Ottawa and 290 km northwest from Montreal in the Administrative Region of Outaouais. The nearest facility is Clova, a former forestry village that’s now serving several outfitters’ lodges. Clova is also a station of the Abitibi railway (ViaRail).

Length: 1,271 km (from source to mouth)

Loss of elevation: The river descends approximately 400m from an elevation of 430m at the headwaters to 20m at its mouth.

Flow as measured at Carillon Dam: Average flow: 1,950 m3/s, Historic minimum: 301 m3/sec in 1971, and Maximum flow: 8190 m3/sec in 1976

Area of drainage basin (watershed): 146,300 km2. Stretches from Shining Tree in the west to St. Jerome in the east; from Westport in the south to Launay in the north; from Algonquin to Aiquebelle, from Temiscaming to Tremblay. It is twice the size of New Brunswick and larger than many countries, including Greece, Portugal, Switzerland, England, Scotia, Bulgaria, Cuba, and Denmark.

Elevation extremesQuebec: Mont-Tremblant (875m). Ontario: Ishpatina (693m).

Terrestrial Ecozones: Boreal Shields and Mixedwood Plains

Parks within the Watershed

Ontario: Lake Evelyn Smoothwater Provincial Park, Larder River Provincial Park, Mattawa River Provincial Park, Samuel de Champlain Provincial Park, Westmeath Provincial Park, Ottawa River Provincial Park, Algonquin Provincial Park, Upper Madawaska River Provincial Park, Lower Madawaska River Provincial Park, Lake St. Peter Provincial Park, Driftwood Provincial Park, Fitzroy Provincial Park, Bon Echo Provincial Park, Sharbot Lake Provincial Park, Rideau River Provincial Park, Silver Lake Provincial Park, Voyager Provincial Park and Murphy’s Point Provincial Park.
Quebec: Gatineau Park (NCC), Mont-Tremblant Québécois Park, d’Aiguebelle Québécois Park, Oka Québécois Park, Plaisance Québécois Park, La Vérendyre Québécois Wildlife Reserve, Papineau–Labelle Québécois Wildlife Reserve and Rouge–Matawin Québécois Wildlife Reserve.

Major Tributaries

Upper Ottawa River: Camachigama, Capitachouane, Chochouane, Darlens, Kinojéris, Blanquet and Wabi Creek.
From Lake Temiscaming to the mouth: Kipawa, Montreal, Mattawa (43 km), Petawawa (187 km), Bonnechere (145 km), Madawaska (230 km), Mississipi (169 km), Rideau (146 km), South Nation (161 km), Rigaud, Maganasipi, Dumoine (129 km), Noire, Coulonge (217 km), Gatineau (386 km), du Liévre (330 km), Blanche, Petit Nation (97 km) and Rouge (185 km).

Largest Islands: Allumet, Grand Calumet and Kettle

The Ottawa River is connected to: Lake Ontario by the Rideau Canal system and with the Upper Gatineau River by the diversion from the Cabonga Reservoir in the Gatineau River basin to the Dozois Reservoir (situated in the headwaters of the Ottawa River) through the Barrière dam. The Cabonga-Dozois diversion is opened in order to assure a minimum flow to satisfy the needs of hydroelectric production on the upper Ottawa River. The Mattawa River is a natural passage through the Algonquin Highlands between Lake Nipissing and the Ottawa River. It rises 3.5 km east of Lake Nipissing and flows east along an ancient fault line into the Ottawa River. At one point, the Mattawa River connected Lakes Superior and Huron to the Ottawa River.

Ecological Significance: The Ottawa River Valley is home to at least 24 provincially or nationally imperilled species, including Least Bittern, Spotted Turtle, and American Ginseng. Its microclimate, sand, and limestone substrate sustain rich wetland and forest habitats that support a diversity of flora and fauna. While the region is one of the most threatened landscapes in Canada, it hosts the most biologically diverse ecosystems in Québec. (Source: The Nature Conservancy)

The Ottawa River is also home to a unique and diverse fauna of freshwater mussels. This unique freshwater mussel fauna includes a minimum of 14 different species (27 % of the Canadian freshwater mussel fauna), each one linked to specific fish hosts which ensure the upstream and downstream dispersal of the mussel’s specialized glochidia larvae. In many areas of the Ottawa River, the density of freshwater mussels on the bottom commonly exceeds 100 individuals per square metre. This is a very high value compared to other rivers in Eastern Canada. (Source: André Martel – Canadian Museum of Nature)