Stillwater · Old Red Sandstone · Wales / Brecon Beacons (Taff Valley)

Llwyn-on Reservoir

Llwyn-on Reservoir — Reflections

Llwyn-on is the largest of the three Taff reservoirs at a hundred and fifty acres and the most accommodating — fly, spinner or worm all permitted, which makes it a favourite with local anglers and a good water to bring a beginner to.

Fair · Rainbow
Diawl Bach · 12-14
Fairlive now
Reasonable summer fishing likely at Llwyn-on Reservoir
Good wave on — drift country. A useful wave. Work the productive shore.
62% confidence
What moved it
  • WindNE 11 km/hLight breeze
Today's fly
Diawl Bach
Diawl Bach12-14
Washing-line, sub-surface
Conditions on the water
Live gauge
Wind
Light breeze
NE 11 km/h
N
NE
from the north-east
Wave20 cm ripple
Water temp—
Air temp14°C
CloudClear
Pressure1023 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 Llwyn-on Reservoir. The ripple should help fish move and feed more confidently.
Where
Start with Booby (8-10) on a fast strip on floating line or static on sinking. 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. In the ripple, a bushy searching dry (Hopper, Shipman's, Elk Hair Caddis) outperforms flush emergers — it stays visible and holds the surface tension.
The plan
Plan A

Start with Booby (8-10) on a fast strip on floating line or static on sinking. 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. In the ripple, a bushy searching dry (Hopper, Shipman's, Elk Hair Caddis) outperforms flush emergers — it stays visible and holds the surface tension.

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

Evening tends to be the best period in summer — stay late if you can for a sedge or spinner fall.

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

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Beyond the hatch · worth watchingambient prey

Hatch predictions

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Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
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
Gammarus Scud (Olive)
Gammarus Scud (Olive)
10-14 · Gammarus Scud
Washing-line, sub-surface
Bays & launches · 1
Llwyn-on Reservoir — day ticket via Fishing PassportAccess varies
The largest of the three Taff Valley reservoirs at 150 acres — bookable on the Fishing Passport with day-ticket bag limits of four or six fish, or a junior two-fish permit.
What's coming
Plan ahead
5-day outlook
Condition match
66%
Cloud25%
Wind100%
Temp60%

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

Other water nearby · 5
Beacons Reservoir
7.0 km
Brown trout · Rainbow trout
Afon Cynon
9.0 km
Brown trout
Llyn Cwm Llwch
10 km
Brown trout
Talybont Reservoir
11 km
Brown trout
Bargoed Park
17 km
Brown trout · Rainbow trout
Gallery · 2
  1. Llwyn-on Reservoir — Reflections
    Reflections
  2. Terrain map of the venue
    Terrain map
About this water

Llwyn-on is the largest of the three Taff reservoirs at a hundred and fifty acres and the most accommodating — fly, spinner or worm all permitted, which makes it a favourite with local anglers and a good water to bring a beginner to. Stocked with rainbows and browns; the bag-limit permits run four or six fish. Bookable by day-ticket through the Fishing Passport. The Taff valley setting is broad and pastoral rather than dramatic, but the fish are honest and the access is straightforward.

  • Reservoir
  • Old red sandstone
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.
Related guides
Big Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatchThermal Layers & Troutreading depth and temperature
Booking & contacts