Spate · Mixed · South Wales / Cardiff / Caerphilly

River Rhymney

The River Rhymney flowing past Bedwas in South Wales, a gently curving rural river stretch bordered by trees.

Down the Rhymney Valley from the head of the South Wales coalfield through Bedwas and the eastern Cardiff suburbs to the Severn estuary.

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.
90% confidence
What moved it
  • Level0.18 mLast reading 13h ago
  • Water temp22.3°C
  • ClarityClear
Today's fly
CDC Emerger
CDC Emerger16-18
Upstream dry, in the film
Conditions on the water
Live gauge
Level
Steady
0.18 m
Last reading 13h ago
Water temp22.3°C
ClarityClear
Weather29°C
WindW 17 km/h
Pressure1019 hPa
Rain · recent0.0 mm
Rain · ahead0.1 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

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 valley; fly life improving with catchment recovery.
Where
Middle Rhymney through the valley above the Cardiff suburbs. Pool tails and runs through farmland.
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 22.3°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayPeak at 6am

Hatch predictions

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Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

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Evidence
Survey-backed · regionalHigh confidence

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

Through the year
0–3 scale · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Salmon runRun
1
2
2
2
2
1
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

Wild-river first principles. Early-season nymphs and practical searching, then dry flies, emergers and spiders as hatches and surface activity improve.

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 Rhymney flowing past Bedwas in South Wales, a gently curving rural river stretch bordered by trees.
    The River Rhymney at Bedwas, South Wales, looking west along a quiet rural stretch.
  2. Terrain map of the venue
    Terrain map
About this water

Down the Rhymney Valley from the head of the South Wales coalfield through Bedwas and the eastern Cardiff suburbs to the Severn estuary. Another industrial-recovery story — wild brown trout through the middle valley, sewin on the autumn lifts, the salmon side a genuine rumour rather than a fishery. Like its neighbours the Taff and Ely, the Rhymney is more interesting than its postcode would suggest, and the recovery work continues.

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

NRW WFD Cycle 3 — Rhymney (conf Nant Cylla to Chapel Wood, Bedwas): Good ecological status. Corrected 2026-06-18 from a Nant-Glandulas tributary tag (was recorded Moderate). Source: NRW DataMapWales WFD Cycle 3 classification layer.

EA (England) · GB109057027280

The full read · show the working · for Brown Trout · confidence 90%
How the 10 is built — score × weight = contribution
Temperature5 × 28%1.4
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time70 × 13%9.1
Pressure80 × 7%5.6
Insect activity55 × 12%6.6
Limiting factor: Water temperature (22.3°C) is outside Brown Trout's preferred range (10–16°C)= 57
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.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Salmon 1 May → 17 October
  • Sea trout 3 March → 17 October
  • Trout 3 March → 30 September

Sea trout: Variable seasonal (2026) — Recovering industrial valley river; sewin work up on autumn lifts in modest numbers. All-Wales At Risk picture applies. The Rhymney's value as a fishery is in its recovery, not in destination angling.

Related guides
Yorkshire & SpidersNorth Country methodsEuro Nymphingsubsurface methods
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