Tailwater · Mixed · Idaho

Big Lost River

A river meanders through a wide agricultural valley with a viewing bench and interpretive sign in the foreground and snow-covered mountains behind
Prime · Brown Trout
Sparkle Dun · 14-18
Primelive now
About as good as it gets
River steady at a fishable height. On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
90% confidence
What moved it
  • Level0.82 mLast reading 13h ago
  • Water temp10.3°C
  • ClarityClear
Today's fly
SD
Sparkle Dun14-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
0.82 m
Last reading 13h ago
Water temp10.3°C
ClarityClear
Weather27°C
WindS 7 km/h
Pressure1016 hPa
Rain · recent5.9 mm
Rain · ahead4.8 mm

Live readings — water temperature is an estimate where the gauge does not record it.

Water temperature for Brown Trout
Ideal
10°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — conditions well-balanced, with water temperature particularly in your favour.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 4 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 3 guilds with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Western Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Pale Morning DunHatch
2
3
3
2
TricoHatch
2
3
2
Black MidgeHatch
2
3
3
3
3
3
3
3
3
3
3
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
  • Idaho licence
  • Flow is irrigation-controlled and can change overnight
  • Special-regulation reaches apply — check Idaho Fish & Game.
What's coming
Plan ahead
5-day outlook
Gallery · 2
  1. A river meanders through a wide agricultural valley with a viewing bench and interpretive sign in the foreground and snow-covered mountains behind
    The Big Lost River winding through its valley near Mackay, Idaho, below the snow-capped Lost River Range
  2. Terrain map of the venue
    Terrain map
Water quality · US Clean Water Act
  • Aquatic life: Impaired
What this classification means

EPA ATTAINS assessment unit 'Big Lost River - McKay Reservoir Dam to Beck and Evan Ditch' (ID17040218SK011_05), 2022 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Temperature. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · ID17040218SK011_05

The full read · show the working · for Brown Trout · confidence 90%
How the 87 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time85 × 13%11.1
Pressure80 × 7%5.6
Insect activity65 × 12%7.8
Conditions total= 87
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
Directions
Apple MapsGoogle Maps
Seasons & zones
  • TroutSaturday of Memorial Day weekend → 30 November
Related guides
Euro Nymphingsubsurface methods
Booking & contacts