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.
Water supply and sanitation in Canada
The water supply of Montréal is taken from lac Saint-Louis, lac des Deux-Montagnes, Rivière des Prairies and the St. Lawrence River. This water is then treated in seven plants with a daily capacity of 2,917,000 m³ for 1.8 million residents and industries, businesses and institutions. The river receives untreated liquid waste from metropolitan Montreal and the newly developed suburbs by way of over 150 discharge outlets. Whenever there is significant rainfall on the island of Montreal, household sewage is mixed with the city street rainwater and discharged untreated into the river.
The Rivière des Prairies used to receive massive discharges of untreated waste water from the city, turning it into essentially an open sewer; however, ecological intervention and modern waste water treatment mostly reversed the damage and the river is often considered clean by the RSMA(Réseau de suivi du milieu aquatique), and suitable for swimming. A CAN$10 billion investment program is underway in Montreal to upgrade water treatment plants, to replace ageing water pipes and to install roughly 23,000 meters for industries, businesses and institutions until 2013.