About the Watershed

The Kootenay River – 2nd largest Columbia River Tributary

Geography

The Kootenay or Kootenai River Basin is an international watershed encompassing about 18,000 square miles of British Columbia, Northwest Montana and Northern Idaho. The Kootenai River originates just North of Kootenay National Park. From there is flows 485 miles through Montana and Idaho, eventually returning to Canada and Kootenay Lake. Basin topography is dominated by steep mountainous country, 90% of which is forested or above tree-line. It drops nearly 1,805 meters (5,914 feet) in elevation as it flows through the basin.

Rainfall is relatively plentiful throughout the basin, making it the second largest tributary of the Columbia River system in terms of runoff volume, though it is only the third largest in terms of drainage area. Only the Snake River contributes more volume, and does so from a much larger watershed area.

Kootenai River Basin Location

The Kootenai River sub-basin is an international watershed that encompasses parts of British Columbia, Montana, and Idaho. The headwaters of the Kootenay) River are located just North of Kootenay National Park, B.C. The River flows South through Kootenay Park and down the Rocky Mountain Trench, where it slows at the reservoir (Lake Koocanusa) which was created by Libby Dam.

From the reservoir, the river turns West, passes through a gap between the Purcell and Cabinet Mountains, enters Idaho, and then loops north where it flows into Kootenay Lake, BC. The water flows through the West arm of Kootenay Lake and then South to join the Columbia River at Castlegar, BC.

In terms of runoff volume, the Kootenai River is the second largest tributary of the Columbia River. In terms of watershed area (36,000 km2 or 8.96 million acres), it ranks third biggest in the Columbia River system. (Knudson 1994).

Drainage Area

Nearly two-thirds of the Kootenai’s 485-mile-long channel, and almost three-quarters of its watershed area, is located within the province of British Columbia. Roughly twenty-one percent of the watershed lies within the state of Montana, and six percent falls within Idaho (Knudson 1994). The Continental Divide forms much of the eastern boundary, the Selkirk Mountains the western boundary, and the Cabinet Range the southern. The Purcell Mountains fill the center of the J-shaped course the river takes on its way to Kootenay Lake.

Climate

The sub-basin has a relatively moist climate, with annual precipitation even at low elevations generally exceeding 20 inches. Warm, wet air masses from the Pacific bring abundant rain and 1,000 to 7,500 mm (40 to 300 inches) of snowfall each year. In winter, Pacific air masses dominate and produce inland mountain climates that are not extremely cold, although subzero continental-polar air occasionally settles over the mountains of northern Idaho and vicinity.

The Continental Divide Range, with crest elevations of 10,000 to 11,500 feet along nearly 250 km (155 miles) of ridgeline, is a major water source for the Kootenai River. The range receives 2,000 to 3,000 mm (80 to 120 inches) of precipitation annually (Bonde 1987). Some of the high elevation country in the Purcell Range around Mt. Findlay receives 2,000 mm (80 inches) of precipitation a year; but most of the range, and most of the Selkirk and Cabinets, get only 1,000 to 1,500 mm (40 to 60 inches) annually (Daley et al. 1981). In the inhabited valley bottoms, annual precipitation varies from just under 500 mm (20 inches) at Rexford, Montana (USACE 1974) and Creston, British Columbia (Daley et al. 1981) to just over 1,000 mm (40 inches) at Fernie, British Columbia (Oliver 1979).

Topography

The drainage basin is located within the Northern Rocky Mountain physiographic province, which is characterized by north to northwest trending mountain ranges separated by straight valleys that run parallel to the ranges.

The topography of the Kootenai River sub-basin is dominated by steep, heavily forested mountain canyons and valleys. Consequently, nearly all of the major tributaries to the river, including the Elk, Bull, White, Lussier, and Vermilion Rivers have a very high channel gradient, particularly in their headwaters. In contrast, the main stem of the Kootenay has a fairly low channel gradient after entering the Rocky Mountain Trench near Canal Flats. The river drops less than 1,000 feet (305 meters) in elevation from Canal Flats to Kootenay Lake, a distance of over 300 miles (480 km). However, even along the river’s slow meandering course, valley-bottom widths are generally less than two miles and are characterized by tree-covered rolling hills with few grassland openings. The only exceptions to this topography are the slightly wider valley bottoms in the Bonners Ferry-to-Creston area and the Tobacco Plains, located between Eureka, Montana and Grasmere, British Columbia.

Synder and Minshall (l996) identified three different geomorphic reaches of the Kootenai River between Libby Dam and Kootenay Lake. The first reach (Canyon) extends from Libby Dam to the Moyie River (92 km). It flows through a canyon in places, but otherwise has a limited flood plain due to the closeness of the mountains. The substrate consists of large cobble and gravel.

The second reach (Braided) extends from the Moyie River to the town of Bonners Ferry (7.5 km). It is extensively braided with depths that are typically less than 9 m, and substrates that consist mostly of gravels. The river has an average gradient of 0.6 m/km, and velocities higher than 0.8 m/s. The third reach (Meander) extends from just below the town of Bonners Ferry to the confluence of the Kootenay Lake (82.5 km). Here, the river slows to an average gradient of 0.02 m/km, deepens, and meanders through the Kootenai Valley back into British Columbia and into the southern arm of Kootenay Lake. The meandering section through the Kootenai Valley is characterized by water depths of up to 12 meters (40 feet) in runs and up to 30 meters (100 feet) in pools (Snyder and Minshall 1994). This reach has been extensively diked and channelized, which restricts the natural ecological function of the River.

Geology

Mountains in the sub-basin are composed of folded, faulted, and metamorphosed blocks of Precambrian sedimentary rocks of the Belt Series and minor basaltic intrusions (Ferreira et al. 1992). Primary rock types are meta-sedimentary argillites, sitlites, and quartzites, which are hard and resistant to erosion. Where exposed, they form steep canyon walls and confined stream reaches. The porous nature of the rock and glaciation and have profoundly influenced basin and channel morphology (Hauer and Stanford 1997).

The river character changes dramatically from a bedrock-controlled regime in Montana to a silt/clay regime near the town of Bonners Ferry, Idaho. During the Pleistocene, continental glaciation overrode most of the Purcell Range north of the river, leaving a mosaic of glacially scoured mountainsides, glacial till, and lake deposits.

Late in the glacial period, an ice dam blocked the outlet at West Arm of Kootenay Lake. The dam formed glacial Kootenay Lake, the waters of which backed all the way to present-day Libby, Montana.

Glacial Kootenay Lake filled the valley with lacustrine sediments, which included fine silts and glacial gravels and boulders. The Kootenai River and lower tributary reaches in Idaho are actively reworking these lacustrine sediments today. A terrace of lacustrine sediments on the east side of the valley is approximately 150 feet above the current floodplain and is a remnant of the ancestral valley floor.

Tributary streams working through remnant deposits to meet the present base level of the mainstem and from the mainstem reworking existing floodplain and stream bank deposits continue to be a source of fine sediments.

An extensive network of marshes, tributary side channels, and sloughs were formed by lowering of the lake level, flooding, and the river reworking its floodplain. Some of these wetlands continued to be supported by groundwater recharge, springtime flooding, and channel meandering. Much of this riverine topography however, has been eliminated by dyking and agricultural development, especially in the reach downstream of Bonners Ferry, Idaho.

Hydrology

The headwaters of the Kootenay River in British Columbia consist primarily of the main fork of the Kootenay River and Elk River. High channel gradients are present throughout headwater reaches and tributaries.

Libby Reservoir (Lake Koocanusa) and its tributaries receive runoff from 47 percent of the Kootenai River drainage basin. The reservoir has an annual average inflow of 10,615 cfs. Three Canadian rivers, the Kootenay, Elk, and Bull, supply 87 percent of the inflow (Chisholm et al. 1989). The Tobacco River and numerous small tributaries flow into the reservoir south of the International Border.

Major tributaries to the Kootenai River below Libby Dam include:

• Fisher River (838 sq. mi.; 485 average cfs)
• Yaak River (766 sq. mi. and 888 average cfs)
• Moyie River (755 sq. mi.; 698 average cfs)

Kootenai River tributaries are characteristically high-gradient mountain streams with bed material consisting of various mixtures of sand, gravel, rubble, boulders, and drifting amounts of clay and silt, predominantly of glacio-lacustrine origin.

Fine materials, due to their instability during periods of high stream discharge, are continually abraded and redeposited as gravel bars, forming braided channels with alternating riffles and pools. Streamflow in unregulated tributaries generally peaks in May and June after the onset of snow melt, then declines to low flows from November through March. Flows also peak with rain-on-snow events. Kootenai Falls, a 200-foot-high waterfall and a natural fish-migration barrier, is located eleven miles downstream of Libby Montana.

The river drops in elevation from 2.200 metres at the headwaters to 532 metres at the confluence of Kootenay Lake. It leaves Kootenay Lake through the West arm to join with the Columbia River at Castlegar.

A natural barrier at Bonnington Falls, plus a series of four dams isolate fish from other populations in the Columbia River basin. The natural barrier has isolated sturgeon for approximately 10,000 years (Northcote 1973). At its mouth, the Kootenai River has an average annual discharge of 868 m3/s (30,650 cfs)

Soils

Soils formed from residual and colluvial materials eroded from Belt rocks or in materials deposited by glaciers, lakes, streams, and wind. Wind deposits include volcanic ash from Cascade Range volcanoes in Washington and Oregon.

In many areas, soils formed in glacial till and are generally loamy and with moderate to high quantities of boulders, cobbles, and gravels. Although soils within the mountainous regions vary widely in character, most mountain and foothill soils are on steep slopes and well drained, with large amounts of broken rock. Rock outcrops are common.

Soils deposited by glaciers or flowing water are, for the most part, deep, well-drained, and productive soils. Most of forest soils in the subbasin are somewhat resistant to erosion by water. In most of the valleys, soils are deep, relatively productive, and gently sloping.

Ustolls, Ochrepts, and Ustalfs are the dominant soils in valleys and on lower mountain slopes. Ochrepts, Borolls, and Orthents are dominant on upper mountain slopes and crests. Orthents and areas of rock outcrop are extensive on steep mountain slopes, and Fluvents and Aquolls are in valleys (NRCS 2000).

Land Use

(ECONOMIC BASE)
The Kootenay Basin remains relatively remote and sparsely populated. Fewer than 100,000 people live within the basin upstream from Kootenay Lake, an area larger than the states of Maryland and Delaware combined.

The largest municipal center is Cranbrook-Kimberley (population of 25,000). Only a handful of other communities have populations larger than 2,000. They include Libby, Montana, Bonners Ferry, Idaho; and Fernie, Sparwood, Elkford, and Creston, British Columbia.

The forest products industry remains the most dominant employment and most extensive development activity in the sub-basin. Roughly 90 percent of the drainage is forested. Logging and associated road building has occurred in nearly all of the lower elevation valleys and on many higher elevation ridges. Roadless areas larger than 5,000 acres are uncommon. Nine roadless areas totaling 139,600 acres exist in the Idaho portion of the sub-basin (IPNF 1991). In the Montana portion, nine roadless areas totaling 241,500 acres are present, including approximately 60,000 acres of upper Libby and Lake creeks within the Cabinet Mountains Wilderness Area (USDA 1987). The largest contiguous block of land without logging roads in the British Columbia portion of the Kootenay Basin is the 390,000-acre Kootenay/Mt. Assiniboine National and Provincial Parks (Rocchini 1981). Approximately 150,000 acres of the headwaters of the St. Mary River and Findlay Creek northwest of Cranbrook/Kimberley are within the Purcell Wilderness Conservancy. The total surface area of undeveloped areas amounts to about 10 percent of the Kootenai(ay) Sub-basin above Kootenay Lake.

Coal and hard rock mining are prominent activities in the sub-basin, particularly along the Elk and St. Mary rivers and in the northern Cabinet Mountains. Large-scale, open-pit coal mining began in the Elk River watershed in the early 1970s. Since the late 1930s, the Sullivan Mine at Kimberley, B.C. has been the largest metal producer in the basin. In 1981 it was one of the two largest lead-zinc mines in the world (Daley et al. 1981). From 1981 to the present, a large copper and silver mine and chemical floatation mill has operated in the Lake Creek watershed south of Troy, MT.

About two percent of the sub-basin is agricultural land, much of it used for pasture and forage production (Bonde and Bush 1982). Agricultural development is confined primarily to narrow valley bottoms. Though it utilizes a relatively small area, it has had a large impact on habitats of the main stem river and tributary mouths because most of the activity occurs in the floodplain. The largest contiguous block of agricultural land is within the Purcell Trench, which extends roughly from Bonners Ferry, Idaho to the river’s entry into Kootenay Lake. Production of oats, wheat and barley account for 62 percent of the agricultural output in the Bonners Ferry/Creston area, with livestock production accounting for 20 percent. Hay and grass seed production and livestock grazing are the most common agricultural activities in the rest of the sub-basin.

The two largest industrial operations and point-source discharges to the Kootenay River are the Crestbrook Forest Industries’ pulp mill in Skookumchuck, B.C. and the Cominco mining, milling, and fertilizer plant in Kimberley, B.C. (Daley et al. 1981).

Another industrial operation in the basin was the mining and processing of vermiculite by the W.R. Grace Company northeast of Libby, MT on Rainy Creek.

Protected areas in British Columbia

The Kootenay River arises near to and flows through 1,406 square kilometer Kootenay National Park, one of 5 National Parks that represent the Rocky Mountain natural region of Canada.

Kootenay River Ranch, Canal Flats a 3100 acre property consisting of a flat, low plateau bordering the Kootenay River on the east side of the valley floor.

The Middle Bummer’s Flat Project consists of 260 hectares of marsh and rangeland that is an extension of an existing Ducks Unlimited project. Bummer’s Flat consists of three separate marsh compartments along the Kootenay River that have been managed under a Ducks Unlimited Canada conservation agreement.

Just before the Kootenay River reaches Kootenay Lake, it passes through the Creston Valley Wildlife Management Area (CVWMA) a 17,000 acre wetland of international significance. The CVWMA’s mission is to manage the wetlands for conservation and natural species diversity through research, education and public support.

Protected areas in Montana and Idaho
Natural areas and lands designated to protect wildlife and associated habitats include the Dancing Prairie (TNC), Myrtle Creek Game Preserve (managed by USFS), Cabinet Mountain Wilderness Area (USFS), and several Natural Research Areas (RNA’s) that are managed by the USDA Forest Service. Other wildlife management areas include the Kootenai National Wildlife Refuge (USFWS), Lost Trail National Wildlife Refuge (USFWS), Woods Ranch Wildlife Management Area (MFWP), West Kootenai Wildlife Management Area (MFWP), Kootenai Falls Wildlife Management Area (MFWP), Boundary Creek Wildlife Management Area (IDFG), and McArthur Lake Wildlife Management Area (IDFG). Lands specifically managed for ESA-listed or sensitive species include USFS management zones for grizzly bear, woodland caribou, wolverine, and lynx.

Dams

The production of hydroelectric energy is an important industry in the sub-basin. Along with the Libby Dam/Libby Reservoir complex, by far the largest human-made structure in the watershed, six smaller hydroelectric dams are located in the U.S. part of the sub-basin on the Elk, Bull, Moyie, and Goat Rivers and Smith and Lake Creeks . In addition there are five hydroelectric dams on the lower Kootenay River in British Columbia.

Libby Reservoir, formed by impoundment of the Kootenai River in 1972, is a 90-mile-long storage reservoir with a surface area of 188 km2 (46,500 acres) at full pool. It is operated by the Army Corps of Engineers (USACOE) and located in Lincoln County, northwest Montana, approximately 27 km (17 mi.) upstream from the town of Libby. The Montana portion of the reservoir is bordered mainly by the Kootenai National Forest. The majority of the private property is located near the town of Rexford on the eastern side of the reservoir. The land along the Canadian portion of the reservoir is mostly private. Kikomun Provincial Park is located on the east bank of the reservoir, 10 miles south of the town of Wardner, BC.

The primary benefit of the project is power production. The surface elevation ranges from 697.1 m (2,287 feet) to 749.5 m (2,459 feet, full pool). The typical operation schedule for Libby Dam and Libby Reservoir begins in July, when the reservoir fills to full pool. Drawdown begins in September and reaches minimum pool elevation in April. Historically, the USACOE operated Libby Reservoir to reach full pool in July and began drafting in September to reach a minimum pool elevation by April and frequently by March 15. Presently, operations are dictated by a combination of power production, flood control, recreation, and special operations for the recovery of ESA-listed species, including Kootenai River white sturgeon, bull trout, and Snake River salmon stocks in the lower Columbia River.