Thousands of cfs, set in Seattle
Everything on this river starts with the outflow from Libby Dam, and the Army Corps of Engineers Seattle District publishes it. Its Libby Dam page carries a flow update with reservoir elevation, inflow, outflow and the scheduled hourly changes, and links the Northwest River Forecast Center outflow forecast under the code KBDM8. The numbers are posted in kcfs, thousands of cubic feet per second, and they move in big steps: 4.0 kcfs at the end of April 2025 ramping to 10.5 on May 1, 20 to 25 kcfs through much of May 2024, a step down to 7 kcfs in late June 2025, 20 and 21 kcfs over Christmas 2025. The gauge on this page sits just below the dam and reads those releases almost directly.
Dave Blackburn's Kootenai Angler in Libby, guiding here since 1982, labels 4,000 cfs the minimum flow, says at 8,000 some wade fishing is possible with caution, calls 13,000 mid-range and 25,000 the maximum. Big Sky Fishing puts prime floating between 8,000 and 12,000 cfs. That gives the 4,000 to 12,000 range on this page: wade near the bottom of it, float the top of it. Big Sky also warns that unannounced releases can raise the river fast, so a wading plan needs an exit. Long-term means are lowest in March and April, about 6,200 and 6,500 cfs, and highest in December, near 16,100, when the reservoir is drawn down for winter. In the two weeks to September 24, 2026 the river held between 6,180 and 6,860 cfs.
Libby Dam to Libby: the upper seventeen miles
The dam is 422 feet high and backs Lake Koocanusa ninety miles upstream, forty-two of them in Canada. It was dedicated in August 1975 and runs five turbines. Below it the river picks up the Fisher River almost immediately, and Highway 37 follows the water most of the way to Libby, seventeen miles downstream, so the bank is easy to reach from the road. A boat ramp about a mile below the dam is the standard put-in, with several more ramps before town. Four miles down is Jennings Rapid, a short Class III. Kootenai Angler notes the tailwater averaging 56 degrees in late September, which is why hoot-owl closures do not come here.
China Rapids, Kootenai Falls and the Troy water
Below Libby the river runs twenty-two quiet miles to China Rapids, another Class III, and two miles later goes over Kootenai Falls, the largest undammed falls in Montana. Take out above the falls; the portage is not optional, and the two miles below hold several Class IV rapids with no exit once you commit. On foot, the falls and the Swinging Bridge downstream are reached by trail from the parking area on U.S. 2. From the falls to the Idaho line the river passes Troy, and a campground and ramp at the Yaak River confluence give good access on a lower river that flows mostly through private ground. The state record rainbow, 33.1 pounds and 38.62 inches, came from the Kootenai at the David Thompson Bridge on August 11, 1997.
The 28-inch rule, the brown trout order and closed fish
The Kootenai sits in FWP's Western District and has its own entry in the 2026 regulations. From Libby Dam to the Highway 37 bridge near the Fisher River, the season is June 1 through February 28, you may keep 1 rainbow a day with a 28 inch minimum, and lures and flies must have single points, no doubles or trebles. From the Highway 37 bridge to the Idaho border the river is open all year, the rainbow limit is 4 including 3 under 13 inches and only 1 over 18, and fishing is closed June 1 through September 30 within 150 yards of the Quartz Creek mouth. Brown trout have no limit; any brown caught between the dam and Kootenai Falls must be killed and the whole fish taken to FWP within 10 days, and browns caught above the falls must be reported within 24 hours at 406-752-5501. Bull trout and white sturgeon are closed to angling and must be released at once. Kokanee snagging is open from Kootenai Falls to 0.8 miles below the Swinging Bridge from September 15 through November 30. The U.S. Fish and Wildlife Service counts 760 Kootenai sturgeon in 2000, down from about 7,000 in the late 1970s, living from the falls downstream.
Redbands by the month
Kootenai Angler points out that the Kootenai drainage holds the only native rainbows in Montana, the Columbia redband, and its monthly calendar is the best guide to them. March and April bring blue-winged olives, the little Iron Dun, Skwalas, little yellow stones and midges while the rainbows spawn. Grannom caddis and Western March Browns appear mid-May to early June, PMDs begin in mid to late June, and for a week or two big black ants cover the water. July and August are the dry fly months: heavy afternoon and evening PMD and tan caddis hatches, green drakes in early to mid July, and hoppers. In September and October the water clears to twenty feet of visibility, olives blanket overcast days, and dries run from a size 8 Cinnamon Sedge down to a 24 Little Blue Quill. Big Sky Fishing adds that leaders of 12 to 15 feet are normal and that the biggest fish below the dam eat five-inch streamers and kokanee imitations.