Stillwater · Limestone · North Wales / Denbighshire

Alwen Reservoir

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

Alwen Reservoir

Robin Mulligan - CC BY 2.0

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
Good summer conditions for Alwen Reservoir
Good wave on — drift country. A useful wave. Work the productive shore.
64% confidence
What moved it
  • WindSW 11 km/hLight breeze
Today’s fly
OD
Olive Damsel10-12
Retrieve, sub-surface
Conditions on the water
Live gauge
Wind
Light breeze
SW 11 km/h
N
SW
from the south-west
Wave20 cm ripple
Water temp—
Air temp13°C
CloudBroken
Pressure1021 hPa
Rain · recent0.0 mm

Some readings unavailable — check directly before fishing.

How to fish it · for rainbow
When
Current conditions suit Alwen Reservoir well for summer tactics. 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.

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
88%
Cloud100%
Wind100%
Temp60%

Conditions are ideal for Alwen Reservoir — wind, cloud and temperature all line up.

Other water nearby · 5
Llyn Brenig
3.0 km
Rainbow trout · Brown trout
Tyn Y Fron Fishing
16 km
Rainbow trout · Brown trout
Llyn Crafnant
21 km
Brown trout · Rainbow trout
Tan-y-Mynydd Trout Fishery
21 km
Rainbow trout · Brown trout
Llyn Coedty (Coedty Reservoir)
23 km
Brown 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.
  • Cloud cover (cloud) suits the fishery well.
  • Buzzer is in its seasonal window, boosting the chance of targeted feeding.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout15 March → 5 October
Related guides
Big Stillwater Playbookreservoir tacticsReservoir Entomologymatching the hatchThermal Layers & Troutreading depth and temperature
Booking & contacts