Stillwater · Limestone · North Wales / Denbighshire, GB-WLS

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.

Good · Rainbow
Booby · 10-12
Goodlive now
Reasonable autumn fishing likely at Alwen Reservoir
Useful ripple, fishable wave. Fishable ripple — drift the productive shore.
70% confidence

Alwen Reservoir is often best in spring through autumn.

What moved it
  • WindSE 22 km/hModerate breeze
Today's fly
Booby
Booby10-12
Washing-line, sub-surface
Conditions on the water
Estimate
Wind
Moderate breeze
SE 22 km/h
N
SE
from the south-east
Wave40 cm chop
Water temp11.5°C
Air temp13°C
CloudOvercast
Pressure1014 hPa
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
The buzzer is on at Alwen Reservoir.
Where
Start with Cormorant (10-12) — on the bob / top dropper. 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.
The plan
Plan A

Start with Cormorant (10-12) — on the bob / top dropper. 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

Buzzer may strengthen through the middle of the day as conditions warm.

Bank

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

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
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
57%
Cloud50%
Wind30%
Temp100%

A reasonable day here, though wind 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
Llyn Elsi
16 km
Brown trout
Llyn Bodgynydd
19 km
Brown trout · Rainbow trout
Llyn Bychan
20 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 (windy) are not ideal for this water.
  • 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
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
Boards & regulators