Churchill River, Labrador, 856 km long (to head of Ashuanipi River), issues from Ashuanipi Lake, drops 75 m over Churchill Falls, broadens into Winokapau Lake and runs east through a deep glacial gorge past Happy Valley-Goose Bay into Lake Melville, Hamilton Inlet, entering the Atlantic near Rigolet (pop 317).
The Athabasca River is the longest river in Alberta (1,538 km). The first 168 km (located in Jasper National Park) are designated as a Canadian Heritage River. As a tributary to the Mackenzie River, water flowing on the Athabasca River eventually drains into the Arctic Ocean. River flow is highest during the summer and lowest during winter, and it is ice-covered from mid-November to mid-April.
The South Saskatchewan River (1,392 km long) is a heavily utilized water source in southern Alberta and Saskatchewan and is a major tributary to the Saskatchewan River, ultimately discharging to Hudson Bay. Mean flow is 280 m3/s, but varies throughout the year, largely controlled by several dams and reservoirs along the river system. The South Saskatchewan River flows through an agriculturally productive region and is prone to periodic droughts and floods.
The Saskatchewan River is 1,939 km long from the Rocky Mountains headwaters to Cedar Lake in central Manitoba. When including its longest tributary, the South Saskatchewan River, the Saskatchewan River is the fourth-longest river in Canada. It’s a major tributary to the Nelson River, ultimately draining into Hudson Bay. Its name is derived from the Cree word kisiskâciwanisîpiy meaning swift-flowing river. The Saskatchewan River was a major transportation route for First Nations for thousands of years and was an instrumental transportation and resource corridor during the fur trade and early European exploration.
The North Saskatchewan River (1,287 km long, the first 48.5 km of which is designated as a Canadian Heritage River) is a major tributary to the Saskatchewan River, which ultimately flows into Hudson Bay. The mean annual flow is 241 m3/s; however, flow varies between the peak in July and minimum in February. It served as a major transportation route from the end of the last Ice Age through the mid-20th century.