Stillwater · Limestone · North Wales / Denbighshire

Alwen Reservoir

Wide landscape view of Alwen Reservoir, North Wales, the open water set among upland moorland and hills.

Alwen is a working reservoir in the Vale of Clwyd — workhorse water rather than pilgrimage site, but none the worse for it.

Fair · Rainbow
Olive Damsel · 10-12
Fairlive now
Reasonable summer fishing likely at Alwen Reservoir
Water temperature is the limiting factor today, not the wave. Fish dawn or dusk if you go at all, and handle everything with extra care.
54% confidence

Alwen Reservoir is often best in spring through autumn.

What moved it
  • WindSW 9 km/hLight breeze
Today's fly
OD
Olive Damsel10-12
Retrieve, sub-surface
Conditions on the water
Live gauge
Wind
Light breeze
SW 9 km/h
N
SW
from the south-west
WaveRipple
Water temp—
Air temp27°C
CloudBroken
Pressure1021 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 Alwen Reservoir. The ripple should help fish move and feed more confidently. Very warm conditions — trout have a narrower safe zone of cool, oxygen-rich water. Fish only at first light or last light, use barbless hooks, keep fish in the water during release, and stop if fish struggle to recover.
Where
Start with Diawl Bach (12-14) — on the bob / top dropper — slow figure-of-eight retrieve. Evening can produce explosive surface takes — try a foam beetle or booby on a long leader. Rainbows respond to more active retrieves — try short strips between pauses.
The plan
Plan A

Start with Diawl Bach (12-14) — on the bob / top dropper — slow figure-of-eight retrieve. Evening can produce explosive surface takes — try a foam beetle or booby on a long leader. Rainbows respond to more active retrieves — try short strips between pauses.

Plan B

Fish early and late, try deeper during the heat of the day with a fast-sinking line.

Watch for

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

Bank

Bank-only venue. Fish from accessible margins, points, weed edges, and inflows.

Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 3 with Pro.

Start free trial

14-day free trial. Cancel anytime.

Through the year
0–3 scale · August 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

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
69%
Cloud70%
Wind100%
Temp25%

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

Other water nearby · 5
Llyn Brenig
3.0 km
Rainbow trout · Brown trout
Llyn Clywedog (Saron)
7.0 km
Brown trout
Tyn Y Fron Fishing
16 km
Rainbow trout · Brown trout
Llyn Elsi
16 km
Brown trout
Llyn Bodgynydd
19 km
Brown trout · Rainbow trout
Gallery · 5
  1. Wide landscape view of Alwen Reservoir, North Wales, the open water set among upland moorland and hills.
    Alwen Reservoir
  2. Llyn Alwen reservoir in Conwy, North Wales, the open water and surrounding landscape in winter light.
    Llyn Alwen
  3. Llyn Alwen reservoir in Conwy, North Wales, the open water and moorland shoreline in winter conditions.
    Llyn Alwen
  4. Alwen Reservoir dam during a spill event, water cascading over the overflow weir.
    Alwen Reservoir dam
  5. Terrain map of the venue
    Terrain map
About this water

Alwen is a working reservoir in the Vale of Clwyd — workhorse water rather than pilgrimage site, but none the worse for it. Managed by Welsh Water for public fishing, it produces reliable rainbow and brown trout on buzzers and nymphs from spring through to autumn. The smaller scale (compared to Vyrnwy) means fish are concentrated and accessible; bank fishing is the standard method. Olives and buzzers hatch from April, sedges from June. The limestone geology supports consistent fertility. A no-fuss, straightforward day on the water with a realistic chance of sport — exactly what many fly fishers want.

  • Reservoir
  • Limestone
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Unknown
What this classification means

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

NRW (Wales) · GB31133976

Why this score
  • Wind conditions (ripple) closely match what this water fishes best in.
  • Buzzers are in their seasonal window, boosting the chance of targeted feeding.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 15 March → 5 October
Related guides
Big Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatchThermal Layers & Troutreading depth and temperature
Casting instructors near here
Booking & contacts
Clubs & associations