Stillwater · Mixed · Black Mountains, South East Wales (Bannau Brycheiniog / Usk catchment)

Grwyne Fawr Reservoir

Calm reflective water of Grwyne Fawr Reservoir surrounded by grassy Black Mountains hillsides under a partly cloudy sky.

The most remote of Wales's reservoir fisheries — a 30-acre stone dam impoundment high in the Black Mountains, walk-in only, with genuinely wild, unstocked brown trout running small (8oz-2lb) in a dramatic, isolated valley.

Fair · Trout
Daddy Long Legs · 10-12
Fairlive now
Reasonable autumn fishing likely at Grwyne Fawr Reservoir
Good wave on — drift country. A useful wave. Work the productive shore.
62% confidence

Grwyne Fawr Reservoir is often best in spring through autumn.

What moved it
  • WindSW 9 km/hLight breeze · Gusts to 31 km/h
Today's fly
Daddy Long Legs
Daddy Long Legs10-12
Upstream dry, on top
Conditions on the water
Estimate
Wind
Light breeze · Gusts to 31 km/h
SW 9 km/h
N
SW
from the south-west
WaveRipple
Water temp8.9°C
Air temp11°C
CloudOvercast
Pressure1019 hPa
Rain · recent0.0 mm

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

Head to
Wind driftW wind
Eastern end

A westerly has held for two days, running warmer than the water (12°C air against 9°C water). Expect fish at the eastern end — the bank it is blowing into — where the drift piles food, colour and warmth together. This reads the upper water, though — a bottom bait at range feels it far less than a floater or a fish in the margins. Treat it as a tiebreaker between good swims rather than an override — features and angling pressure usually count for more.

How to fish it · for Trout
When
Settled weather with some breeze — this is an exposed, high-altitude water
Where
Start with Daddy Long Legs (10-12) on a As per local method. If that does not produce, switch depth or speed before changing the pattern entirely.
The plan
Plan A

Start with Daddy Long Legs (10-12) on a As per local method. If that does not produce, switch depth or speed before changing the pattern entirely.

Plan B

A fry-imitating pattern stripped through the margins can save a blank in autumn.

Watch for

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

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 2 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 4 as a supporter.

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Through the year
0–3 scale · October highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Heather FlyHatch
2
2
Daddy Long LegsHatch
2
3
2
Claret DunHatch
2
3
2
Murrough (Great Red Sedge)Hatch
2
3
2

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

Ranked for today
Trout fly box

Traditional wild-trout llyn fishing. Wet flies and dabblers stay central, with buzzer, caddis, terrestrials and occasional small fry patterns becoming important as the season warms.

BU
Bumble
10-12 · Pattern
Fish it in the film
Bays & launches · 1

Walk-in only — nearest car park is Blaen-y-Cwm, with a track following the Grwyne Fawr river up the valley to the reservoir.

Glanusk EstateEnquiry
Remote, unstocked wild brown trout water controlled by the same estate that holds Usk river beats downstream.
Visit official site ↗
What's coming
Plan ahead
5-day outlook
Condition match
73%
Cloud50%
Wind100%
Temp60%

A good match for Grwyne Fawr Reservoir — most conditions are close to what it fishes best in.

Other water nearby · 5
Llynfi
8.0 km
0
Brown trout · Grayling · Chub
Talybont Reservoir
18 km
Brown trout
Llyn Cwm Llwch
24 km
Brown trout
Beacons Reservoir
27 km
Brown trout · Rainbow trout
Arrow
27 km
Brown trout · Grayling
Gallery · 2
  1. Calm reflective water of Grwyne Fawr Reservoir surrounded by grassy Black Mountains hillsides under a partly cloudy sky.
    Grwyne Fawr Reservoir
  2. Terrain map of the venue
    Terrain map
About this water

The most remote of Wales's reservoir fisheries — a 30-acre stone dam impoundment high in the Black Mountains, walk-in only, with genuinely wild, unstocked brown trout running small (8oz-2lb) in a dramatic, isolated valley. The dam itself is worth knowing the story of: authorised by an Act of Parliament in 1910, it took 16 years to build (delayed by the First World War) via a 12-mile narrow-gauge railway that was reportedly never formally approved for its route, serving a workers' settlement nicknamed 'Tin Town' that housed up to a thousand people and was dismantled within weeks of the dam's completion in 1928. It's now controlled by Glanusk Estate, the same estate that holds Usk river water downstream.

  • Reservoir
  • Mixed
Why this score
  • Wind conditions (ripple) closely match what this water fishes best in.
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
  • Reservoirs of this kind fish well at this time of year.
Related guides
Scotland Playbookloch & river fishingThermal Layers & Troutreading depth and temperatureEuro Nymphingsubsurface methods
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