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.

Marginal · Rainbow
Booby · 10–12
A patient day, if you fancy it
Good wave on — drift country. Slow going — pick your moments and do not force it.
42% confidence
limited data
What moved it
  • WindS 13 km/hGentle breeze · Gusts to 23 km/h
Today's fly
Booby
Booby10–12
Washing-line, sub-surface
Conditions on the water
Estimate
Wind
Gentle breeze · Gusts to 23 km/h
S 13 km/h
N
S
from the south
Wave20 cm ripple
Water temp6.3°C
Air temp1°C
CloudOvercast
Pressure1018 hPa
Rain · recent0.0 mm

No gauge on this water — readings are regional estimates from weather, not a live gauge.

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 Autumn Buzzer (12–14) — on the bob / top dropper — slow figure-of-eight retrieve. Early in the day, try buzzers on a slow figure-of-eight or a booby on a fast-sink line near the bottom. Rainbows respond to more active retrieves — try short strips between pauses.

Plan B

Slow down everything. A booby on a fast-sinking line, left static, can pick up deep fish.

Watch for

Keep an eye on changing conditions — wind shifts and cloud breaks can trigger short feeding spells.

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 2 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 as a supporter.

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Through the year
0–3 scale · November highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
Reservoir BuzzerHatch
2
3
3
3
3
3
2
Daphnia SwarmHatch
2
3
3
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.

Buzzer team todayfor the conditions now
Point
Bloodworm
Not in this water's box
#10
How to fish it
Slow-sink line · slow figure-of-eight, pausing to let the flies hang

Fly recommendations

Point fly shown — supporters see the whole team, sizes and why.

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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
54%
Cloud70%
Wind65%
Temp25%

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

Other water nearby · 5
Alwen Reservoir
3.0 km
Brown trout · Rainbow trout
Llyn Clywedog (Saron)
4.0 km
Brown trout
Tan-y-Mynydd Trout Fishery
19 km
Rainbow trout · Brown trout
Llyn Elsi
19 km
Brown trout
Llyn Garth
20 km
Brown trout · Rainbow trout
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

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. Fished all year: stocked weekly from March to September, then winter fishing on a three-fish permit, with pike (all returned) from October to February from pegs or boats. Closed for ten days in early March for stocking. Visitor centre and boats from sailing club end.

Surface area
3.7 km² (908 acres)
Length
4.0 km (2.5 mi)
Width
1.6 km (1.0 mi)
Area © OpenStreetMap contributors. Length and width: Wikipedia, Llyn Brenig
  • Reservoir
  • Slate
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Unknown
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
  • winter conditions with overcast skies and breezy wind.
  • Reservoirs of this kind fish hard at this time of year.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 14 March → 2 March
  • Pike 1 October → 28 February
Related guides
Fly Fishing in North and Mid Walesfeatured in this guideBig Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatch
Casting instructors near here
Booking & contacts
Boards & regulators
At a glance

Llyn Brenig is a reservoir in Denbighshire / Hiraethog moors, Wales. The catchment geology is recorded as slate, and the water sits at about 415 m above sea level. Species listed for this water: rainbow trout, brown trout and pike. The trout season is recorded as running from 14 March to 2 March. The pike season is recorded as running from 1 October to 28 February. Best window recorded for anglers: May to September (prime); late March–April fishable but cold and slow-hatching. Core methods listed: washing line; buzzer; drifting wet flies. Its Water Framework Directive ecological status is recorded as moderate. Nearby waters in our listings include Alwen Reservoir at 3.0 km, Llyn Clywedog (Saron) at 4.0 km and Tan-y-Mynydd Trout Fishery at 19 km.