Upland Reservoir · Slate · Powys / Upper Severn headwaters, GB-WLS

Llyn Clywedog

Open water of Llyn Clywedog reservoir from the shoreline, hills and sky reflected in the calm surface.
Good · Rainbow
Daddy Long Legs · 10-12
Goodlive now
Good autumn conditions for Llyn Clywedog
Good wave on — drift country. Drift fishing weather — three flies on a long leader.
69% confidence
What moved it
  • WindSE 7 km/hLight breeze
Today's fly
Daddy Long Legs
Daddy Long Legs10-12
Upstream dry, on top
Conditions on the water
Estimate
Wind
Light breeze
SE 7 km/h
N
SE
from the south-east
WaveRipple
Water temp12.5°C
Air temp14°C
CloudBroken
Pressure—
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
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 Daddy Long Legs (10-12) on a As per local method. 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

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

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 3 guilds as a supporter.

Start free trial

14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 5 as a supporter.

Start free trial

14-day free trial. Cancel anytime.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
2
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.

Ranked for today
Fly box · Rainbow
BU
Bumble
10-12 · Pattern
Fish it in the film
What's coming
Plan ahead
5-day outlook
Condition match
77%
Cloud70%
Wind65%
Temp100%

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

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)
  • Ecology: Moderate
  • Chemical: Unknown
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
  • Temperature (cool) is in the sweet spot for autumn fishing.
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
  • Reservoirs of this kind fish well at this time of year.
Directions
Seasons & zones
  • Trout Late March → Mid October
Related guides
Casting instructors near here
Booking & contacts