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.
Fraser River
The Water Survey of Canada currently operates 17 gauge stations that measure discharge and water level along the majority of the mainstem from Red Pass just downstream of Moose Lake within the Mount Robson Provincial Park to Steveston in Vancouver at the river mouth. With an average flow at the mouth of about , the Fraser is the largest river by discharge flowing into the Pacific seaboard of Canada and the fifth largest in the country. The average flow is highly seasonal; summer discharge rates can be ten times larger than the flow during the winter.