Check the closure before you load the boat
As of late September 2026 the top of this river is shut. FWP put a 24-hour drought closure on the Beaverhead from Clark Canyon Dam to Pipe Organ FAS starting September 1, after outflows from Clark Canyon Reservoir were cut to 50 cfs on September 1 and to 25 cfs on September 10. The regular spawning closure on that reach runs October 1 through the third Saturday in May, and FWP says it stays in place regardless of conditions, so in practice the upper river will not reopen until the May 2027 opener. The Barretts gauge read between 55.7 and 92.6 cfs over the two weeks to September 24. Below Pipe Organ the river is still legal to fish under the season rules further down this page, but at these flows it is a wading proposition only.
Clark Canyon Dam to Barretts: fifteen miles of willows
Frontier Anglers in Dillon calls the stretch from the dam to Barretts Diversion fifteen miles of trophy trout water, and it is the reason people drive here. It is narrow and willow-lined the whole way, rarely more than 70 feet bank to bank according to Sunrise Fly Shop, so casts are short and tight to the brush. The first seven miles, dam to Pipe Organ, are the most crowded and hold the most fish; Frontier says that reach carries the highest numbers in the Jefferson drainage. Sunrise names two runs guides talk about, the Axel Hole and the Slick, and both shops warn about floating moss starting a little above Henneberry in summer.
Access comes off the I-15 frontage roads south of Dillon. High Bridge FAS is a hand launch about 14 miles south of town, reached from the recreation road exit. Henneberry FAS, a couple of miles down the same road, has a gravel ramp, day use on the east bank and dispersed primitive camping on the west, plus walk-in parking about a mile upstream. Pipe Organ FAS, off the Dalys exit, has a concrete ramp just over the bridge, and Grasshopper FAS, at the Grasshopper exit about 11 miles south of Dillon, has another. Corrals FAS, 9 miles south of town on the frontage road, is walk-in only.
What the Barretts gauge is telling you
There is no hydropower at Clark Canyon; the dam stores water for irrigators and they decide the release. Frontier's reports read like an irrigation ledger: 100 cfs in early July 2026, 245 a few days later, about 550 by mid-July, 711 at the end of July 2025. The Barretts gauge sits below the mouth of Grasshopper Creek, so it reads the dam release plus whatever Grasshopper is adding. In spring 2025 Frontier described about 100 cfs from Pipe Organ to Grasshopper and about 150 below it, which is the gap you should expect between the release and this number in a normal spring.
For wading, the shop numbers line up well. Frontier says 125 to 200 cfs through fall and winter is optimal for the fish, that 450 is not too much for wading, and that wading High Bridge to Barretts gets hard around 680. Sunrise calls 376 a great wading flow and a decent floating one; at 148 Frontier found the upper river a difficult float. That is where the 125 to 450 cfs range above comes from. Since the dam went in, July and August are the high months at Barretts, with post-dam means of 807 and 636 cfs, while the Dillon gauge averages under 200 in the same months because water leaves the river at Barretts. Frontier's point about water temperature holds: the release comes off the bottom, so heat is rarely what closes the upper river. Low water is.
Dillon, the Barretts Diversion and the lower river
Below Barretts the Beaverhead winds past Dillon and down the valley to Twin Bridges, where it meets the Big Hole to form the Jefferson. In town, Poindexter Slough, Selway Park off Selway Drive, Cornell Park and Blacktail Meadows give walk-in access. Past the Highway 91 South (Tash) Bridge and Selway Bridge the river runs through ranch ground and the fishing is more about big browns in the undercuts than numbers. This is the reach that gets hoot-owl restrictions in hot summers: in July 2024 it was under 2 p.m. to midnight closures from the Highway 41 bridge near Dillon to the mouth, and FWP lifted the 2025 hoot-owl and full closures on the lower Beaverhead, Ruby and Jefferson on September 5.
Rainbows go back everywhere; browns depend on the reach
The 2026 FWP regulations put the Beaverhead in the Central District but override most of the defaults. Rainbow trout are catch-and-release on the entire river. Clark Canyon Dam to Pipe Organ Bridge is open only from the third Saturday in May through September 30; the 2026 opener was May 16. From the dam to High Bridge FAS, brown trout are catch-and-release and you must use artificial lures with single-pointed hooks. From High Bridge to Barretts Diversion you may keep 5 brown trout daily, all under 18 inches. From Barretts Diversion to the mouth the season is April 1 through September 30 and browns are catch-and-release. On Saturdays from the third Saturday in May through Labor Day, High Bridge FAS to Henneberry FAS is closed to float fishing by nonresidents and to float outfitting, and outfitter use on the river has been capped since 1997. Pipe Organ to Barretts has no season exception, so the district rule of open all year applies there. A Montana conservation license, fishing license and the AIS Prevention Pass are required; nonresidents pay $31.50 all in for a single day.
Sowbugs, PMDs, Yellow Sallies and late crane flies
Most Beaverhead fish are caught under an indicator. The staples in Frontier's reports are small sowbugs in 18 and 20, soft-hackle and hot-bead sowbugs, San Juan worms in natural and burgundy, Zebra Midges and baetis nymphs such as the Psycho May and olive Micro May. Sunrise has winter anglers on a #16 Shop Vac and #18 Micro May under an attractor. The Mother's Day caddis usually shows the first week of May and lasts about a week.
Summer is three overlapping hatches. Frontier says PMDs, Yellow Sallies and caddis run most of the season and hang on into the first week of September, with larger caddis taking over in mid-September; Sunrise puts the peak of PMDs and Sallies earlier, into July. Tricos start around the first week of August and run into early October between the dam and High Bridge, and the big riffle crane flies come in late August and September, when skating a crane fly across the tailouts is a legitimate plan. Dry fly fishing lasts until the cold weather near the end of November.