Fly fishing report · West

Big Wood River

A Big Wood River report for Ketchum and the Wood River Valley, RiverReports/USGS flow checks, IDFG reach rules, hatches, flies, Highway 75 access, and spring-closure planning.

Check flow & weather

Today's river scoreHigh source confidence

Caution

Best option: Wade.

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Updated Jul 13, 11:17 PM UTCUsually refreshes about every 45 minutes

Recommended approachWade

Mode scores adjust the river-wide score for the risks of wading, bank fishing, or floating.

Wade · Best fit66/100

Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

Bank / edge66/100

Bank and edge fishing remains a practical low-commitment option if access is legal and footing is safe.

Float66/100

A float is in play where this report supports boat access and wind, releases, and shuttle logistics are manageable.

Confirm before you leave

Flow and weather right now.

Use the flow trend to confirm the score before you leave. Weather can change the safest and most productive fishing window.

River strategy

Check the reach rules before fishing the Ketchum water.

The Big Wood is a classic Sun Valley trout river, but rules vary by reach and season. Use the Ketchum gauge, then confirm open dates, gear rules, and access before fishing.

Use the Big Wood near Ketchum RiverReports and USGS gauge first.
Check IDFG rules for closures and catch-and-release/barbless-hook sections.
Spring runoff can make wading dangerous and clarity poor.
Lower irrigation and intermittent-flow reaches are not the same plan as Ketchum water.

Why this score moved

FlowUse caution

USGS shows 115 cfs with a stable over about 6 hours trend. same-date USGS history (1948-2025, 39 readings) puts normal around 207 cfs and the lower quartile near 122 cfs; today's flow is below normal for the date. This is below normal, so edge depth, temperature, and pressure matter.

HeatUse caution

The NWS forecast is near 87F. Fish early and verify water temperature where trout stress is possible.

Best mode nowUse caution

Wade: Wading is in play only where your chosen access has clear footing, legal entry, and no forced crossings.

SeasonHelps score

Summer: Post-runoff PMDs, caddis, green drakes, stones, and terrestrials can be excellent.

Public alertsHelps score

No active NWS alert was returned for this forecast point.

Read the water

What changes the plan.

The Big Wood is strongest after runoff drops, water stays cool, and reach rules are open. In high water, warm low water, or closed sections, use a legal alternative.

Low clear summer

Use stealth, longer leaders, and smaller dries or droppers.

Good medium flow

Dry-droppers, caddis, PMDs, and nymph rigs can cover riffles and banks.

Runoff

Avoid unsafe wading and wait for clarity to return.

Warm or low water

Fish early, use a thermometer, and stop if trout recovery is poor.

Field plan

Fish it with intention.

Best flows

Use the RiverReports Ketchum chart and USGS 13135500 together. Stable or slowly falling post-runoff flows create the easiest fly-fishing window; runoff, very low warm water, or lower-valley intermittent conditions should push you toward a different reach or another river.

When to skip

Skip the Big Wood when the reach is closed, when IDFG special-rule language does not match your plan, when runoff makes crossings unsafe, when low warm water stresses trout, or when the only visible access is private bank.

Local plan

Start with the Ketchum and upper Wood River Valley corridor, then decide whether Hailey or lower-valley water is actually suitable that day. Match flies to the flow and temperature instead of treating the whole Big Wood as one uniform river.

Backup water

If the Big Wood is closed, high, warm, or crowded, compare the Big Lost River or Boise River after checking current rules and flows. Smaller tributary ideas should be researched separately before fishing.

Hatches & flies

Bring a flexible box.

TimingWhat to watchUseful flies

SpringBWOs, midges, early caddisBWO emerger, zebra midge, caddis pupa, pheasant tail

Reviewed family · report says “BWO emerger”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide

Reviewed pattern · report says “zebra midge”Zebra MidgeLook for a very slim tapered thread body, evenly spaced contrasting wire rib, a small bead, and no tail or wing. The reviewed classic is black with silver wire and a silver bead. Red, olive, brown, glass-bead, jig-hook, resin-coated, or tailed forms must remain labeled variations rather than replacing the classic identity.See photos & how to fish it + 2 more reviewed guides in the Fly Box

Early summerGreen drakes, PMDs, caddis, golden stonesGreen drake dry, PMD, elk hair caddis, stonefly nymph

Reviewed family · report says “Green drake dry”Green Drake PatternsGreen Drake is a hatch family, not one fly. Large nymph, low emerger or cripple, upright dun, and spent-wing forms remain distinct.See family guide

Reviewed family · report says “PMD”Pale Morning Dun PatternsPMD names an insect group, not one fly. Pale nymphs, trailing-shuck emergers, upright or low-riding duns, cripples, and spent-wing spinners stay visibly separate.See family guide + 2 more reviewed guides in the Fly Box

Late summerTerrestrials, tricos, caddisAnt, beetle, hopper, trico spinner, small caddis

Reviewed family · report says “Ant”Ant PatternsAnt patterns can be foam, fur-bodied, winged, or sunken. The narrow waist and paired body lobes matter more than one material recipe.See family guide

Reviewed family · report says “beetle”Beetle PatternsBeetle flies range from simple foam shells to hair-bodied and sunken forms. A rounded back and compact profile distinguish the family from ants and hoppers.See family guide + 3 more reviewed guides in the Fly Box

FallBWOs, midges, October caddisBWO dry, RS2, October caddis, streamer

Reviewed family · report says “BWO dry”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide

Reviewed pattern · report says “RS2”RS2Start with the beadless architecture: two dark-dun Microfibett tails separated behind a slim, tightly twisted and visibly segmented dubbed abdomen; a fuller thorax; and saddle-hackle web clipped into a short angled wing bud. Rim Chung's original-style form uses natural beaver dubbing and hackle web. CDC- or Antron-wing ties, beads, curved hooks, flash, and tailless Avatar-style flies must remain labeled variations.See photos & how to fish it + 2 more reviewed guides in the Fly Box

Confirm the section is open before fishing in spring.

Fish dry-droppers along banks and broken riffles in summer.

Use lighter tippet and small dries in low clear water.

Move around the valley instead of forcing one pressured access point.

Avoid lower intermittent-flow reaches when they do not support a safe trout plan.

Access & responsibility

Know the entry. Know the exit.

IDFG lists Big Wood River rules by reach, including seasonal closures and special catch-and-release/barbless-hook water. Check current Idaho rules before fishing.

Ketchum and upper valley

The main report focus, using the Big Wood near Ketchum gauge.

Highway 75 reach context

IDFG special rules can apply by milepost and section; check current language.

Wood River Valley USFS access

Useful upper-valley public-land and campground context.

Hailey and lower valley

Different flow, access, and temperature considerations than Ketchum water.

Transparent sources

Check the facts behind the plan.

Last material review: 2026-05-31

flowRiverReports: Big Wood River near Ketchum flowUSGS monitoring location: Big Wood River near Ketchum regulationIDFG Big Wood River Fishing Planner backgroundIDFG Big Wood River Working Group accessUSFS Wood River Valley Area safetyNational Weather Service forecast point near Ketchum

Common questions

Before you leave.

What Big Wood reach does this page cover?+

It focuses on the Ketchum and upper Wood River Valley trout fishery, with lower-valley cautions.

Which gauge should I use?+

Use USGS 13135500, Big Wood River near Ketchum, shown with RiverReports and official USGS context.

Are there spring closures?+

Some Big Wood sections have seasonal closures or special rules. Check IDFG before fishing.

What makes the Big Wood good in summer?+

Post-runoff hatches, clear riffles, and terrestrial banks can be excellent when water remains cool.