Kootenai River, MT

The Kootenay (Kootenai in the U.S. and historically called the Flatbow) is a major river in southeastern British Columbia, Canada and the northern parts of the U.S. states of Montana and Idaho. It is one of the uppermost major tributaries of the Columbia River, and the largest North American river that empties into the Pacific Ocean. The Kootenay River stretches 781 kilometres (485 mi) through the central Rocky Mountains in a region known as the Kootenays.

Born in glaciers and flowing through a rugged landscape of mountains and valleys, this river drains an isolated and sparsely populated region of the Pacific Northwest. Between the highest headwaters and the Columbia River, the Kootenay’s elevation dips by over two kilometers. Although comparable by length, watershed and discharge to the Columbia above where the two rivers meet, the Kootenay is of a very different character. Its dramatic drop, caused by a steep gradient, results in the formation of many rapids.

The Kootenay rises on the northeast slopes of the Beaverfoot Range of southeastern British Columbia, and flows initially southeast through the valleys of Kootenay National Park. Its first few kilometers (miles) are quiet, threading slowly through a series of marshes and small lakes. The river becomes significantly enlarged as it reaches the confluence with the Vermilion River, which is actually the larger of the two where they meet near the settlement of Kootenay Crossing. It continues southeast, receiving the Palliser River from the left, and swings southwards into a gorge at the confluence with the White River.

At the small town of Canal Flats, British Columbia it passes within 2 kilometres (1.2 mi) of Columbia Lake, the headwaters of the Columbia River, as it merges into the Rocky Mountain Trench and the eastern foothills of the Selkirk Mountains. It receives the Lussier River near Skookumchuck Station of the Canadian Pacific Railway and the St. Mary and Wild Horse rivers at the historic mining town of Fort Steele, then the Bull River at the settlement of the same name. At Wardner, British Columbia, the Kootenay widens into the Lake Koocanusa reservoir, formed by Libby Dam over 130 kilometres (81 mi) downstream at Jennings, Montana. Lake Koocanusa, fed by the Elk River (one of the Kootenay's larger tributaries) spans the U.S.-Canada border.

Below Libby Dam the river, now known as the Kootenai, surges around the south side of the Purcell Mountains in what is known as the Big Bend, where it receives the Fisher River from the left and veers to the west, passing the city of Libby. The Kootenai then drops over Kootenai Falls in a gorge, and veers northwest at the town of Troy. The Yaak River and Moyie River join from the north, the latter near the village of Moyie Springs, before and after the Kootenai crosses the Montana-Idaho state line. In Idaho the Kootenai's current slows significantly as it enters the Kootenai Valley, passing the city of Bonners Ferry, where it turns north.

The Kootenai re-enters Canada and becomes the Kootenay again south of Creston, British Columbia, and slows as it enters the Kootenay Flats before broadening into 100-kilometre (62 mi)-long Kootenay Lake, where the Duncan River, the largest tributary, contributes its waters. Near Balfour an arm of the lake branches westwards into canyons near Nelson, where the Kootenay becomes a river again, but not for long. Four more run-of-the river dams impound the river in the 40-kilometre (25 mi) stretch that follows. The river also drops over several waterfalls, including Bonnington and Corra Linn, all of which are taken advantaged of to generate hydropower. At Brilliant it widens into a small inland delta, then at Castlegar it joins with the Columbia River.