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.

Species

A side-water session, not the main event

Low and clear — careful approach country. Long leader, small flies, slower casts.

75% confidence in this read
Water temperature for brown trout
Cool — slow
5°C est.ideal 1016°C
0°14°28°
Why this score · for brown trout
  • Temperature2828% weight
  • Flow8022% weight
  • Clarity9518% weight
  • Feeding Time5013% weight
  • Pressure807% weight
  • Prey Activity2312% weight
Conditions
Level
0.28 m
Water temp
5.4°C
Estimated
Clarity
Clear
Air temp
4°C
Wind
S 14 km/h
Gentle breeze
Pressure
1014 hPa
Rain · 48h
0.2 mm
No meaningful rain
Rain · ahead
9.1 mm
Light rain · next 48h

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

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
Fair conditions. Clarity is favourable (95), Prey activity is weakest (23).
Through the year
0–3 scale · May 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.

Gallery · 1
  1. Terrain map of the venue
    Terrain map
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.
Directions
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
Seasons & zones
  • Trout3rd Saturday of March → 30 September
  • Grayling1 June → 28 February
Other water nearby · 3