Boise River, South Fork

GAGE LOCATION

DAY/YEAR
GRAPHS

CURRENT
STAGE/FLOW

WHAT TIME

S. Fork Boise near Featherville

7 30 year

1.78 / 215

1 am

S. Fork Boise below Anderson Dam

7 30 year

3.57 / 601

11 pm Yest.

CITY

Mountain Home

NOAA

Accuweather

TWC

HATCH

NYMPH/
LARVA

PUPA/
EMERGER

DUN/
ADULT

EGG-
LAYER

Blue-winged olive

Flav

Pale morning dun

Green caddis

Caddis

Golden stonefly

Salmonfly

Cranefly

Midge

Sculpin

Hopper

Baitfish

Beetle

Ant

The river drops in September as the irrigation season ends. Flows of around 600 cfs are typical. That's a good flow for pontoon boats, but hard boats should avoid the river or use extreme care when the river is that low. It is a very wadable flow.

Pink alberts, flavs, and caddis (evenings) provide dry fly action. The pink alberts can be imitated with a size 14-16 pinkish-bodied Parachute Hares Ear, Light Cahill, or Sparkle Dun. The hatch is usually from 3:00 to evening; it usually ends in early September or even late August.

Look for flavs in shady areas after 7:30 p.m. Hatch activity can continue past dark.

For the caddis, try size 12-14 emerger and pupa patterns, such as a Sparkle Pupa or CDC Caddis. Good adult imitations include a Parachute Caddis, X Caddis, or Elk Hair Caddis.

Stonefly nymphs, such as a Kaufmanns Stonefly version of either salmonfly or golden stonefly nymphs will work well, too. Team your stonefly nymph with a small Pheasant Tail, Copper John, Prince, Brassie, etc. Another subsurface strategy is to toss cranefly larva patterns near the edges of the river. Cranefly adult patterns are also effective once those long-legged insects are flying about. For some good cranefly imitations, see Tying Adult Cranefly Patterns.

Later in September, expect hatches of blue-winged olives. The nymphs are always active before the hatch season starts, so a size 18 Pheasant Tail or gold-ribbed Hares Ear can get strikes when dead-drifted near the bottom. That strategy should work all month.

See the Rivers in General section for more September fly fishing tips.