Reading the river flow at a glance
The Semois has a wide navigable range: paddling is allowed from 2.20 m³/s up to 50 m³/s. Between those two limits, flow mainly changes how comfortable the trip is. The table below places each band.
| Flow (m³/s) | Conditions | Navigation | What it means |
|---|---|---|---|
| 0 to 2.2 | Too low | Forbidden | The rocky riverbed and aquatic life are protected. |
| 2.2 to 5 | Very calm | Take care | Rocky bottom sometimes visible; better for experienced paddlers. |
| 5 to 15 | Ideal | Allowed | Clear water, suits all levels, families included. |
| 15 to 30 | Steady current | Allowed | Faster trip; beginners should stay alert. |
| 30 to 50 | Strong current | Take care | Powerful current, not recommended for children under 8 or complete beginners. |
| Over 50 | Flood | Forbidden | No trips. |
Where the measurement comes from
The flow shown comes from the SPW station at Membre-sur-Semois (reference 9434, “Membre Pont”). The official status applies to the stretch of the Semois downstream of the Linglé bridge. It is based on the Walloon Government decree of 19 March 2009 (Article 6). The SPW sets and publishes this status every day.
A sunny day can therefore stay closed if the 72-hour average is too low, and a rainy day can be allowed. Check the reading on the morning itself, then again before you set off.
Cold water: what the level does not tell you
An ideal flow does not guarantee warm water. In spring and autumn the water stays cold even when the air feels mild. A capsize then quickly becomes an ordeal.
- Keep your life jacket fastened, even on calm stretches.
- Pack a fleece and dry clothes in a waterproof barrel.
- Bring a waterproof jacket for showers: rain chills you faster.
- In a headwind, expect more effort; in fog, stay together and spot obstacles earlier.
After rain, before you book
After heavy rain, flow climbs then drops back within a few days. Aim for the window when the river falls back below 30 m³/s, where the current becomes comfortable again for a mixed group. Conversely, after a long dry spell, watch the lower limit: navigation can be suspended to protect the rocky riverbed.
The general rules (life jacket, age, what to do if things go wrong) are set out on the paddling rules page. To choose a route, see the Semois route and the prices.
If the level changes along the way
Flow can change during your trip, especially in rainy weather. Watch the river from the moment you launch: water turning cloudy, a faster current, branches being carried along. These are signs of a rise. If that happens, head for the nearest bank, land only where access is obvious and work out where you are before setting off again. Using the official landing points also avoids damaging the banks.
Comparing with other rivers
If the Semois is closed or too strong, look at the Ourthe water level or the Amblève: their ranges and stations are different.