Ottawa River drainage basin
The Ottawa River drainage basin is the drainage basin in northern North America where surface water empties into the Ottawa River and adjoining waters. Spanning an area of about , it is the 12th largest drainage basin in Canada, occupying the Canadian provinces of Ontario and Quebec. It accounts for about 11% of the total Saint Lawrence River drainage area.
Missouri River
To the north, the much lower Laurentian Divide separates the Missouri River watershed from those of the Oldman River, a tributary of the South Saskatchewan River, as well as the Souris, Sheyenne, and smaller tributaries of the Red River of the North. All of these streams are part of Canada's Nelson River drainage basin, which empties into Hudson Bay. There are also several large endorheic basins between the Missouri and Nelson watersheds in southern Alberta and Saskatchewan. The Minnesota and Des Moines Rivers, tributaries of the upper Mississippi, drain most of the area bordering the eastern side of the Missouri River basin. Finally, on the south, the Ozark Mountains and other low divides through central Missouri, Kansas and Colorado separate the Missouri watershed from those of the White River and Arkansas River, also tributaries of the Mississippi River.