Stillwater · Slate · Denbighshire / Hiraethog moors, GB-WLS

Llyn Brenig

Broad landscape view across Llyn Brenig reservoir on a clear day, moorland hills reflected in calm open water.

919-acre upland reservoir on the Hiraethog moors above Cerrigydrudion.

Fair · Rainbow
Olive Damsel · 10-12
Fairlive now
Reasonable summer fishing likely at Llyn Brenig
Good wave on — drift country. A useful wave. Work the productive shore.
54% confidence
What moved it
  • WindNW 19 km/hGentle breeze
Today's fly
Olive Damsel
Olive Damsel10-12
Retrieve, sub-surface
Conditions on the water
Live gauge
Wind
Gentle breeze
NW 19 km/h
N
NW
from the north-west
Wave40 cm chop
Water temp
Air temp18°C
CloudOvercast
Pressure1019 hPa
Rain · recent0.0 mm

Some readings unavailable — check directly before fishing.

How to fish it · for Rainbow
When
Cold-water upland — buzzers come on later than the southern reservoirs, May through July. Sedges into September; back-end lures before October close. Wait for the air to warm.
Where
Open water boat marks; the dam end and the eastern bays. Brenig's altitude means weather drives the fishing more than season alone.
Method
Floater with buzzers under indicator in late spring; midge-tip with team of three through summer; lures on intermediate when fish are deep.
Kit
10 ft #7 boat rod; floating, intermediate and fast-intermediate lines; 6 to 8 lb fluoro. Drogue and a long-handled net.
The plan
Plan A

Start with Olive Damsel (10-12) — on the point. Rainbows respond to more active retrieves — try short strips between pauses. If that does not produce, switch depth or speed before changing the pattern entirely.

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.

Either bank or boat

Good ripple suits both bank and boat. Bank: work inflows, dam walls, and points. Boat: broadside drift covering wind lanes.

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 3 guilds with Pro.

Start free trial

14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 5 with Pro.

Start free trial

14-day free trial. Cancel anytime.

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

Boat-friendly, competition-influenced, often wind-driven, with strong top-of-water periods but also classic deep searching and washing-line phases.

What's coming
Plan ahead
5-day outlook
Condition match
77%
Cloud70%
Wind65%
Temp100%

A good match for Llyn Brenig — most conditions are close to what it fishes best in.

Other water nearby · 5
Gallery · 6
  1. Broad landscape view across Llyn Brenig reservoir on a clear day, moorland hills reflected in calm open water.
    Llyn Brenig Reservoir
  2. Upland reservoir landscape at Llyn Brenig showing open water amid moorland under a wide sky.
    Llyn Brenig
  3. Wide panoramic view of Llyn Brenig reservoir showing the full breadth of open water under a cloudy sky.
    Llyn Brenig from the western shore
  4. Golden sunrise light over the open water of Llyn Brenig reservoir, North Wales.
    Sunrise over Llyn Brenig
  5. Fishing boats moored on the shore of Llyn Brenig reservoir with open water and moorland hills behind.
    Boats on Llyn Brenig
  6. Terrain map of the venue
    Terrain map
About this water

919-acre upland reservoir on the Hiraethog moors above Cerrigydrudion. One of Wales's premier stillwater trout fisheries — boat and bank. Stocked with brown and rainbow trout, with wild browns breeding in feeder streams. Competition venue. Excellent buzzer, Diawl Bach and damsel fishing. Visitor centre and boats from sailing club end.

  • Reservoir
  • Slate
Water quality (WFD)
  • EcologyModerate
  • ChemicalUnknown
What this classification means

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

NRW (Wales) · GB31133923

Why this score
  • Temperature (moderate) is in the sweet spot for summer fishing.
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
Directions
Seasons & zones
  • Trout 26 March15 October
Related guides
Casting instructors near here
Booking & contacts
Clubs & associations