A legendary waterway among Idaho fly fishing destinations, the Big Wood River is known not only as one of the state’s best trout streams but also as one of its most beautiful. Named for the stately cottonwood trees that line its banks, the Big Wood River was a favorite stomping ground of author and angler Ernes Hemingway. It remains an outstanding place to fish, despite being in the middle of one of Idaho’s biggest tourism areas—the Sun Valley. With conditions that make it both beginner-friendly and challenging, it’s not hard t o see why the Big Wood River’s popularity endures.
The Lay of the Land
From its headwaters just west of Galena Peak in the Boulder Mountains, the Big Wood River flows southeast towards the Sun Valley. The upper portion of the river is fast, narrow, and strewn with boulders, and it’s perfect for anglers who enjoy fishing pocket water.
From the point where the Big Wood River merges with the North Fork, it widens significantly and slows down a bit. From here through the Sun Valley to Ketchum, Hailey and Bellevue, the river takes on the characteristics of a more typical freestone stream, with classic configurations of long runs, fast riffles and deep pools. This 25-mile stretch is the most popular, and it’s perfect for wading.
One of the Big Wood River’s best features is that it’s too small for drift boats, leaving even the most popular sections to anglers willing to walk and wade. With a map and a little willingness to explore, you can also easily reach some sections that are excellent and relatively unpressured.
The final section of the Big Wood River is the tailwater below Magic Reservoir. The conditions below the dam depend heavily on the amount of snowmelt and how much of the river has been diverted for irrigation, but an excellent tailwater fishery is available here when conditions permit.
Trout Species
Rainbow trout are the most abundant trout species in the Big Wood River, inhabiting virtually all of its 137 miles. They tend to run small in the upper river, but rainbows in the Sun Valley section average 12 to 14 inches, and individuals over 18 inches are frequently landed.
Brown trout are also available in the lower part of this section around Bellevue, and in the Magic Reservoir tailwater. They reach sizes comparable to rainbows, but true giants are rare. Fly fishers have also been known to catch some healthy cuttbows here, and there are some beautiful brook trout close to the Big Wood’s headwaters and in some of its tributaries.
The Idaho Department of Fish & Game doesn’t stock the Big Wood River, so it’s a near-certainty that any fish you catch will be wild. The trout here are noted for their spectacular coloration, especially rainbows, which display the large white-tipped fins typical of wild fish.
Matching the Hatch
Hatches on the Big Wood River are prolific and widely varied, and while generic fly patterns can often yield modest success, being able to match the current hatch at any given moment will serve anglers well. There are plenty of opportunities throughout the year to mimic a range of mayfly species, and some solid caddis hatches happen here too.
Blue Winged Olives are arguably the most important mayfly hatch, taking place from March through June and again from September into early November. Pale Morning Duns and Green Drakes hatch in June, followed by smaller Western Green Drakes starting in July, and Tricos and Great Red Quills starting in August.
When it comes to caddisflies, Spotted Sedges typically hatch from June to August, and Green Sedges hatch from July to October. Multiple species of Golden Stoneflies hatch throughout the warmer months, and midges are available year-round, but are of special importance to anglers in winter.
Fly Selection
One of the great things about the Big Wood River is that its conditions are equally accommodating to nymphing and dry fly fishing. Though the former is more consistently effective, this river rewards skilled dry fly anglers who match any of its abundant hatches.
BWO Parachutes, Sparkle Duns and classic Pheasant Tail Soft Hackles in sizes 16 to 22 are all great dry fly choices when Blue Winged Olives are hatching in spring or fall. Golden Stones and Yellow Sallies are important in summer, so be sure to have a big, chunky stonefly imitation handy; Yellow Stimulators and Chubby Yellow Sallies in sizes 8 to 12 are safe bets.
Summer is also the season of terrestrials, making size 6 to 10 Hoppers and size 12 to 16 foam Black Ant patterns effective. Some of the larger trout in the Big Wood River also dine on minnows regularly, so don’t leave home without a few Sculpins or Muddler Minnows in sizes 6 to 12.
Nymphing is the way to go when trout aren’t rising, and a lot of traditional patterns—Hare’s Ear, Copper John, Pheasant Tail, Prince Nymph—can be effective. Sizes 14 to 18 are generally just about right. Particularly effective on the Big Wood River are the Caddis Pupa and Green Rockworm nymphs, which mimic the bright-green larva and pupa of the Green Sedge caddisfly. They’re essential in late summer and early fall.
Lastly, midge flies are good any time, but especially in winter when little else is hatching. Tiny Zebra Midge nymphs as small as size 24 are the best bets to catch trout from January through March.
Big Wood River Access
The upper portion of the Big Wood River is paralleled by Route 75 and the Harriman Trail—an 18-mile hiking and biking route—both of which provide ample access. This part of the river meanders in and out of National Forest land, and there are several Forest Service campgrounds on or near the river.
The Hulen Meadows Bridge and Adams Gulch Road each allow river access in the Sun Valley area. The Big Wood River flows directly through the city of Ketchum, where there are numerous riverside parks and public access sites including Hemingway/Northwood Natural Area and Ketchum Rotary Park. The Wood River Trail offers access to several sections of the river.
Downriver through Hailey and Bellevue, some of the top spots to fish the Big Wood River include Draper Wood River Preserve and Howard Preserve. Numerous bridge crossings also provide informal access sites throughout the area.