Attawapiskat River, 748 km long, formed by the confluence of the Pineimuta, Trading and Otoskwin rivers at Attawapiskat Lake, in northeastern Ontario, flows east, jogs north and runs east to the flatland by James Bay. Its drainage area is 50 200 km2 and its mean discharge 626 m3/s.
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.