Annual large river flow

The map shows the six major drainage areas in Canada, the major diversions in 1975 and the flow (in cubic metres per second) of rivers whose mean annual flow at the outlet of their river basin exceeds 400 cubic metres per second. The Mackenzie and the St. Lawrence rivers have the two largest annual flows. The world's largest river, the Amazon, has an average discharge of 212,000 cubic metres per second; more than one-sixth of the world's total river discharge. The Congo, second largest, has an average discharge of 39,600 cubic metres per second, less than one-fifth the flow of the Amazon. The largest river in North America, the Mississippi, has an average discharge of 17,300 cubic metres per second. Canada's largest, the St. Lawrence, discharges 10,100 cubic metres per second, at Nicolet; her second largest, the Mackenzie, flows into the Arctic Ocean with a mean annual discharge of 9,910 cubic metres per second. Discharges for the map were estimated at the river mouth or where the river crossed the Canada-United States border. To obtain these estimated discharges, the gauging station closest to the river mouth or the international boundary was used as an estimate of the gauged portion of the river basin. . In some instances, an upstream gauging station was used if better discharge records were available, or if it had a considerably longer period of discharge data.