Continental Divide

Also known as the Great Divide, the Continental Divide is the line following the HEIGHT OF LAND that separates areas drained by rivers that flow to opposite sides of the North American continent. In Canada, the water flowing in rivers eventually reaches the sea in either the Arctic, Atlantic or Pacific oceans.

The line dividing rivers flowing west to the Pacific from drainage to the Arctic and Atlantic is easiest to visualize, since it lies along the main ranges of the ROCKY MTS. Often it is convenient to use such natural boundaries for human organization, and the Alberta-British Columbia border follows the divide for a considerable distance, as does the border between the YUKON and NORTHWEST TERRITORIES.

 The divide running across the interior of Canada is low and less obvious. This line starts from a point somewhere in the COLUMBIA ICEFIELD of the Rockies from which the 3 axes of the Continental Divide diverge. It follows a line through southern Alberta and SASKATCHEWAN, north of which drainage flows to the Arctic through the PEACE, ATHABASCA and MACKENZIE rivers, or to HUDSON BAY by the North and South SASKATCHEWAN and NELSON rivers. Rivers south of this line are part of the Missouri-Mississippi system.

The divide swings into the US south of the RED RIVER which flows north into MANITOBA. The divide continues into Canada, separating drainage going north and that entering the GREAT LAKES - ST LAWRENCE RIVER basin.

Along the much-eroded SHIELD in QUÉBEC and Labrador, the divide is indistinct, permitting the diversion and transfer of water from rivers south of the divide to south-flowing rivers, as developed in the JAMES BAY PROJECT. Although the divide is used as the Québec-Labrador border, the low relief along which the line is presumed to lie makes it hard to demarcate on the ground.