Tailwater · Mixed · Idaho

Big Lost River

River Livet venue image
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The Big Lost is a desert tailwater below Mackay Reservoir, and it earns its name — downstream it disappears into the lava sinks of the Snake River Plain, going nowhere on the map at all.

Species

A proper day on the water

River steady at a fishable height. A proper day for it.

75% confidence in this read
Water temperature for brown trout
Cool — slow
9°C est.ideal 10–16°C
0°14°28°
Why this score · for brown trout
  • Temperature8228% weight
  • Flow8022% weight
  • Clarity9518% weight
  • Feeding Time5013% weight
  • Pressure807% weight
  • Insect activity6212% weight
Conditions
Level
0.92 m
Water temp
9.0°C
Estimated
Clarity
Clear
Air temp
21°C
Wind
SW 18 km/h
Gentle breeze
Pressure
1012 hPa
Rain · 48h
0.0 mm
No meaningful rain
Rain · ahead
0.0 mm
No meaningful rain · next 48h

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

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
Good — water clarity is right today, though time of day could be better.
Through the year
0–3 scale · June highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Black MidgeHatch
2
3
3
3
3
3
3
3
3
3
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Western Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Pale Morning DunHatch
2
3
3
2

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

Gallery · 1
  1. Terrain map of the venue
    Terrain map
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.
Directions
Apple MapsGoogle Maps
About this water

The Big Lost is a desert tailwater below Mackay Reservoir, and it earns its name — downstream it disappears into the lava sinks of the Snake River Plain, going nowhere on the map at all. The river below the dam holds surprisingly good rainbows and a few big browns in cold, clear water, though the flow is entirely at the mercy of irrigation demand and can change overnight. It's lightly fished, out on its own in big sagebrush country. When the release is right it's a quiet little gem; when the farms need water it's a different river.

  • Mixed
Seasons & zones
  • TroutSaturday of Memorial Day weekend → 30 November