Kootenay River - Watershed

Watershed

At 50,298 square kilometres (19,420 sq mi) in size, the Kootenay river's watershed is one of the largest sub-basins of the Columbia Basin. Its drainage basin encompasses an area almost 400 kilometres (250 mi) from north to south and 250 kilometres (160 mi) from east to west, roughly defining a region of the Pacific Northwest known as the Kootenays. The term "Kootenays" is loosely defined and refers to the whole region of the central Rockies, Selkirks and Purcells (Percells in the U.S.) in southeastern British Columbia (BC), and does not necessarily mean the area drained by the river in Canada. (Across the U.S. border, the moniker no longer applies.) Over 70 percent of the Kootenay's watershed is in Canada while the Montana and Idaho portions occupy 23 and 6%, respectively. The Kootenay is one of the few major rivers in North America that begin in one country, cross into another, and return to the first—others include the Milk River, a tributary of the Missouri River; the Souris River, a tributary of the Assiniboine River; and the Kettle River, a tributary of the Columbia River. It is the third largest tributary of the Columbia by drainage basin and discharge.

The Kootenay River is defined by rocky uplands and steep mountains, and there is relatively little flat land in the watershed. Most of the reasonably level terrain lies in the narrow Kootenay River valley from Bonners Ferry to Kootenay Lake and in parts of the Rocky Mountain Trench from Canal Flats to Lake Koocanusa. Mountain ranges in the region generally trend from northwest to southeast and define drainage patterns with their steep and dramatic vertical relief, with the exception of the Kootenay itself which cuts westwards at its southern bend. Of the Kootenay's many tributaries, the 206-kilometre (128 mi)-long Duncan River is the largest. Hundreds of other tributaries join the river in its winding course, including the Vermilion, Cross, Palliser, White, Wild Horse, St. Mary, Elk, Fisher, Yaak, Moyie, Goat, and Slocan rivers.

Many river basins border on the Kootenay—some are part of the Columbia Basin, while others drain to distant shores of the North American continent. On the south and southeast, the divide formed by the Cabinet and Whitefish ranges separate the Kootenay and Flathead River watersheds. The Flathead is a tributary of the Clark Fork River-Pend Oreille River system which borders the Kootenay watershed on the southwest. The upper Columbia River basin forms the boundary on the north, and the Kicking Horse River watershed also borders the north side of the Kootenay basin. To the southwest is the Priest River, a Pend Oreille tributary. On the east side, over the Continental Divide, the Bow River and Oldman River take rise. Both are tributaries of the South Saskatchewan River, which is part of the Hudson Bay drainage basin.