Upland Reservoir · Slate · Powys / Upper Severn headwaters

Llyn Clywedog

Open water of Llyn Clywedog reservoir from the shoreline, hills and sky reflected in the calm surface.
Fair · Rainbow
Coch-y-Bonddu Beetle · 10-14
Fairlive now
Reasonable summer fishing likely at Llyn Clywedog
Good wave on — drift country. A useful wave. Work the productive shore.
50% confidence
What moved it
  • WindW 9 km/hLight breeze
Today's fly
CY
Coch-y-Bonddu Beetle10-14
Upstream dry, on top
Conditions on the water
Live gauge
Wind
Light breeze
W 9 km/h
N
W
from the west
WaveRipple
Water temp
Air temp11°C
CloudOvercast
Pressure1014 hPa
Rain · recent0.0 mm

Some readings unavailable — check directly before fishing.

How to fish it · for Rainbow
When
Late spring start — May through September is the practical window. Buzzers May into June; sedges through summer; lures for the back-end. Mountain weather changes fast.
Where
Open water boat marks; the dam and the deeper bays. Clywedog's depth means fish go down quickly in summer warm.
Method
Floater with buzzers under indicator in late spring; midge-tip in summer; sweeping line with lures when fish hold 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 (8-12) — 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

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

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 2 with Pro.

Start free trial

14-day free trial. Cancel anytime.

Through the year
0–3 scale · July 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
59%
Cloud50%
Wind65%
Temp60%

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

Other water nearby · 5
Gallery · 2
  1. Open water of Llyn Clywedog reservoir from the shoreline, hills and sky reflected in the calm surface.
    Llyn Clywedog Reservoir
  2. Terrain map of the venue
    Terrain map
Water quality (WFD)
  • EcologyModerate
  • ChemicalUnknown
What this classification means

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

NRW (Wales) · GB30937446

Why this score
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
Directions
Seasons & zones
  • Trout Late MarchMid October
Related guides
Casting instructors near here
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