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.
Afvandingsområdet for disse ni floder ligger i begge lande; Dertil ligger en del af afvandingsområdet for yderligere seks floder — Fraser, Assiniboine, South Saskatchewan, Saskatchewan, Nelson og Winnipeg — i USA, selv om hele deres hovedløb ligger i Canada.