List of longest rivers of Canada
Nine rivers in this list cross international boundaries or form them. Four—the Yukon, Columbia, Porcupine, and Kootenay—begin in Canada and flow into the United States. Five—the Milk, Pend d'Oreille, Saint Lawrence, Red, and Saint John—begin in the United States and flow into Canada. Of these, the Milk and the Kootenay cross the international border twice, the Milk leaving and then re-entering the United States, the Kootenay leaving and then re-entering Canada. The drainage basins of these nine rivers extend into both countries; in addition, the drainage basins of six others—the Fraser, Assiniboine, South Saskatchewan, Saskatchewan, Nelson, and Winnipeg—extend into the United States even though their main stems flow entirely within Canada.
Rainwater Basin
Starks first recognized that the larger of these basins are approximately elliptical to elongate in shape. The larger and semi-elliptical of these basins typically measure about by . Most basins are closed depressions that hold runoff from the surrounding landscape to form seasonal lakes and wetlands in them. Some of these basins have been naturally "breached", or drain to an outside watershed, and no longer hold precipitation run-off. Many of the large semi-elliptical to elliptical Rainwater Basins have a crescent-shaped ridge that Stark referred to as a "lunette" located on the southeast side of them. These distinctive ridges are about in relief.