Spate · Mixed · South Wales / Cardiff

River Ely

The River Ely flowing through green banks near Cardiff, Wales
Contributor photo

The River Ely, Cardiff, Wales

Jeremy Segrott, CC BY 2.0

Small Vale-of-Glamorgan river through Llantrisant and the western Cardiff suburbs to the Bay.

Poor · Brown Trout
CDC Emerger · 16-18
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
80% confidence
What moved it
  • Level0.25 mLast reading 19h ago
  • Water temp21.6°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-18
Upstream dry, in the film
Conditions on the water
Live gauge
Level
Steady
0.25 m
Last reading 19h ago
Water temp21.6°C
ClarityClear
Weather24°C
WindS 5 km/h
Pressure1021 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

Live readings — water temperature is an estimate where the gauge does not record it.

Water temperature for brown trout
Warm — slow
22°C est.ideal 10–16°C
0°14°28°
How to fish it · for brown trout
When
Through the open trout season. Spring olives and summer sedges through the middle reaches; modest fly life compared to the upper Taff.
Where
Upper and middle Ely above the Cardiff suburbs.
Method
Upstream dry to risers through summer; dry-dropper through the runs. Where the river slows through farmland, longer leaders and lighter tippet earn the takes. Spider patterns on the swing when olives are off the water.
Kit
9 ft #4. Floating line, 12 ft leader to 4 to 5 lb fluoro. Wading is usually easy on the lower reaches — the upper valley is rockier.
Why this works
⚠️ Water at 21.6°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots. Otherwise very poor — water clarity is in the right range.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 4 active hatches hour by hour with Pro.

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Evidence
Survey-backed · regionalModerate confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Sea trout runRun
1
2
2
2
2
2
2
1
Trout seasonSeason
1
2
2
2
2
2
1
Daddy Long LegsHatch
2
3
2
March BrownHatch
2
3
2
GrannomHatch
2
2
Large StoneflyHatch
2
3
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
BB
Black Beetle
14-18 · Pattern
Upstream dry, on top
What's coming
Plan ahead
5-day outlook
Water here around 22°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. The River Ely flowing through green banks near Cardiff, Wales
    The River Ely, Cardiff, Wales
  2. Terrain map of the venue
    Terrain map
About this water

Small Vale-of-Glamorgan river through Llantrisant and the western Cardiff suburbs to the Bay. Brown trout in the upper and middle reaches; sewin work up on the autumn lifts but in genuinely modest numbers. The Ely is the smallest of the three Cardiff-area rivers and the least known to fly anglers — an honest urban-recovery fishery rather than a destination.

  • Mixed
Water quality (WFD)
  • Ecology: Poor
  • Chemical: Unknown
What this classification means

NRW WFD Cycle 3 — Ely (conf Nant Clun to Ely, Cardiff): Poor ecological status. Corrected 2026-06-18 from a Nant-Dowlais tributary tag (was recorded Moderate). Source: NRW DataMapWales WFD Cycle 3 classification layer.

EA (England) · GB109057027260

The full read · show the working · for brown trout · confidence 80%
How the 17 is built — score × weight = contribution
Temperature9 × 28%2.5
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity53 × 12%6.4
Limiting factor: Water temperature (21.6°C) is outside Brown Trout's preferred range (10–16°C)= 58
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Sea trout3 March → 17 October
  • Trout3 March → 30 September

Sea trout: Variable seasonal (2026) — Small urban river; sewin work up on autumn lifts in very modest numbers. The Ely is the smallest of the three Cardiff-area rivers and the least established as a migratory fishery. All-Wales At Risk picture applies.

Related guides
Yorkshire & SpidersNorth Country methodsEuro Nymphingsubsurface methods
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