Freestone · Mixed · Wallonia / Luxembourg Province

Semois

Semois venue image
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One of Wallonia's defining southern rivers, winding through wooded valleys and long glides with a mixed trout-and-grayling identity depending on section.

Prime · Brown Trout
Pheasant Tail Nymph · 14-18
Primelive now
About as good as it gets
River steady at a fishable height. On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
75% confidence
What moved it
  • Level0.65 m
  • Water temp15.1°C
  • ClarityClear
Today’s fly
Pheasant Tail Nymph
Pheasant Tail Nymph14-18
Upstream
Conditions on the water
Live gauge
Level
Steady
0.65 m
Water temp15.1°C
ClarityClear
Weather14°C
WindN 11 km/h
Pressure1021 hPa
Rain · recent0.7 mm
Rain · ahead0.7 mm

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

Water temperature for brown trout
Ideal
15°C est.ideal 10–16°C
0°14°28°
How to fish it · for brown trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — water temperature is working for you, but time of day is the limiting factor today.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 11 active hatches hour by hour with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

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
1
Grayling seasonSeason
2
1
1
2
2
2
2
2
2
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
1

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

Ranked for today
Brown Trout fly box
SB
Small Black Beetle
14-18 · Pattern
Upstream dry
Permits & access
Permit required — see local rules.
  • Walloon permit required, but some stretches may sit under additional society, forest-zone or local rights structures depending on section.
What's coming
Plan ahead
5-day outlook
Other water nearby · 2
Lesse
27 km
Brown trout · Grayling
Ourthe
44 km
80
Brown trout · Grayling
Gallery · 1
  1. Terrain map of the venue
    Terrain map
About this water

One of Wallonia's defining southern rivers, winding through wooded valleys and long glides with a mixed trout-and-grayling identity depending on section. More culturally important than flashy, and best treated as a core Belgian river rather than an afterthought behind the better-known East Belgium names.

  • Mixed
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Failing to achieve good
What this classification means

WFD re-coded 2026-06-18: prior id BERW06_SM01R was a wrong-basin code (no row in EEA WISE). Re-mapped to BERW17_SC28R 'Semois III' near the venue coordinate (49.85,5.08, Bouillon area). Status: EEA WISE 2022 (3rd RBMP). Confidence: medium — VERIFY reach against a map (Semois has 4 reaches I–IV). Source: discodata.eea.europa.eu.

WFD classification · BERW17_SC28R

The full read · show the working · for brown trout · confidence 75%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity51 × 12%6.1
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout3rd Saturday of March → 30 September
  • Grayling1 June → 28 February
Related guides
Grayling Playbookgrayling tacticsEuro Nymphingsubsurface methods
Booking & contacts