Stillwater · Granite · North Wales / Gwynedd, GB-WLS

Llyn Trawsfynydd Reservoir

Llyn Trawsfynydd from the shore, open water filling the foreground with moorland hills beyond.
Fair · Rainbow
Olive Damsel · 10-12
Fairlive now
Reasonable summer fishing likely at Llyn Trawsfynydd Reservoir
Good wave on — drift country. A useful wave. Work the productive shore.
54% confidence

Llyn Trawsfynydd Reservoir is often best in spring through autumn.

What moved it
  • WindN 13 km/hGentle breeze
Today's fly
Olive Damsel
Olive Damsel10-12
Retrieve, sub-surface
Conditions on the water
Live gauge
Wind
Gentle breeze
N 13 km/h
N
N
from the north
Wave20 cm ripple
Water temp—
Air temp19°C
CloudClear
Pressure1020 hPa
Rain · recent0.0 mm

Some readings unavailable — check directly before fishing.

How to fish it · for Rainbow
When
Conditions are not ideal but fishable at Llyn Trawsfynydd Reservoir. The ripple should help fish move and feed more confidently.
Where
Start with Olive Damsel (10-12) — on the point. Evening can produce explosive surface takes — try a foam beetle or booby on a long leader. Rainbows respond to more active retrieves — try short strips between pauses.
The plan
Plan A

Start with Olive Damsel (10-12) — on the point. Evening can produce explosive surface takes — try a foam beetle or booby on a long leader. Rainbows respond to more active retrieves — try short strips between pauses.

Plan B

If the main plan stalls, drop to a size 14–16 midge — switch to a washing-line or suspender rig and change drift line before you change food group.

Watch for

Watch for Sedge towards evening — this could be the best window of the day.

Bank

Bank-only venue. Fish from accessible margins, points, weed edges, and inflows.

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 5 with Pro.

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Through the year
0–3 scale · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
2
1
Daphnia SwarmHatch
2
3
3
3
2
Daddy Long LegsHatch
2
3
2
Lake OliveHatch
2
3
3
3
3
3
2
Silverhorns & LonghornsHatch
1
2
2
2
1

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

Ranked for today
Rainbow fly box
What's coming
Plan ahead
5-day outlook
Condition match
52%
Cloud25%
Wind65%
Temp60%

A reasonable day here, though cloud isn't quite in the sweet spot.

Other water nearby · 5
Afon Prysor
1.0 km
Brown trout
Llyn Eiddew Bach
5.0 km
Brown trout
Llyn Eiddew Mawr
6.0 km
Brown trout
Llyn Tecwyn Uchaf
6.0 km
Brown trout · Rainbow trout
Llyn Dubach y Bont
7.0 km
Brown trout
Gallery · 5
  1. Llyn Trawsfynydd from the shore, open water filling the foreground with moorland hills beyond.
    Llyn Trawsfynydd
  2. Llyn Trawsfynydd, Gwynedd — a still lake view with open water and the surrounding upland landscape.
    Llyn Trawsfynydd
  3. Llyn Trawsfynydd lake shore with open water and moorland backdrop under an overcast Welsh sky.
    Llyn Trawsfynydd
  4. The southern end of Llyn Trawsfynydd, open water, a grassy shoreline and the Rhinogydd hills beyond.
    The south end of Llyn Trawsfynydd
  5. Terrain map of the venue
    Terrain map
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Unknown
What this classification means

NRW WFD Cycle 3 (lake) — Llyn Trawsfynydd: Moderate ecological status. Re-tagged 2026-06-18 from a Dwyryd river reach to the reservoir's own lake waterbody. Source: NRW DataMapWales WFD Cycle 3 classification layer.

NRW (Wales) · GB31034870

Why this score
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 15 March → 5 October
Related guides
Big Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatchThermal Layers & Troutreading depth and temperature
Casting instructors near here
Booking & contacts
Clubs & associations