Today’s reading, river by river
Start with the measurement: the table below compares each river with its threshold and updates automatically.
| River | Flow | Water | Paddling |
|---|---|---|---|
| Semois | 7.1 m³/s | 12.4 °C | Allowed |
| Ourthe | 5.6 m³/s | 12.1 °C | Prohibited |
| Amblève | 5.1 m³/s | 10.0 °C | Allowed |
| Lesse | 3.4 m³/s | 13.1 °C | Allowed |
| Meuse | 48.0 m³/s | 12.4 °C | Low water |
The principle: two thresholds, one window
For each river that is open to paddlers, a minimum and a maximum flow define when navigation is allowed. Below the minimum, the riverbed breaks the surface and boats get damaged. Above the maximum, the flood current is powerful and unpredictable. The window in between protects both people and wildlife habitats.
Every river has its own thresholds: the same flow gives a different water depth on a wide, gently sloping river than in a narrow valley.
Thresholds by river
| River | SPW station | Minimum | Maximum | Difficulty |
|---|---|---|---|---|
| Semois | 9434, Membre | 2.2 m³/s | 50 m³/s | Grade I, family-friendly |
| Lesse | 8221, Gendron | 1.5 m³/s | 52 m³/s | Grade I-II |
| Ourthe | 5921, Tabreux | 2.5 m³/s | 65 m³/s | Grade I-II |
| Amblève | L6510, Stavelot | 1 m³/s | 21 m³/s | Grade II-III, whitewater |
| Viroin | 9021, Treignes | 1.6 m³/s | 23 m³/s | Grade I-II |
These values are guidelines: flow changes all the time, which is why you should check the reading on the day of your trip.
Who decides, and on what basis?
Non-motorised boats are regulated by the Walloon Region. The reference text is the Walloon Government decree of 19 March 2009:
- Annex 1 lists the rivers open to boats, and Article 3 allows navigation on those rivers only;
- Annex 2 sets the minimum and maximum flows;
- Annex 3 defines the signage for put-in points;
- the status for the day follows from these thresholds (Article 6).
The measurements come from the SPW hydrometric network. If there is any discrepancy, SPW decrees and data prevail.
River by river
Semois
A family river, 40 to 80 cm deep along much of the routes. The start points mentioned are Alle-sur-Semois and Poupehan. Its navigable range is wide, from 2.2 to 50 m³/s.
Lesse
Between Houyet and Dinant it runs through a tighter valley and stays navigable from 1.5 m³/s. Above 52 m³/s, navigation is suspended.
Ourthe
It winds through the areas around Durbuy and La Roche-en-Ardenne. Its large catchment gives it the highest ceiling, 65 m³/s.
Amblève
The most sporty of the group, with whitewater around Coo and in the Stavelot gorges. The threshold measured at Stavelot applies to the stretch from the Warche confluence to the Cheneux bridge. It is not recommended for beginners or young children.
Viroin
A small tributary of the Meuse in the Viroin-Hermeton Nature Park. Its level rises and falls quickly, so keep a close eye on it.
Meuse
A large-scale waterway, the Meuse is monitored separately from these thresholds. See the Meuse at Waulsort page.
Why river flow changes so fast
Flow responds to rain falling across the whole catchment, sometimes several days earlier and tens of kilometres upstream. After a storm it can double within hours. In a dry summer, a river can drop below its minimum even in glorious weather. Check again on the morning of your trip, and call it off if the river is outside its range.
Several stretches run through Natura 2000 areas or reserves where herons, kingfishers, otters and beavers cope badly with disturbance. The thresholds also help protect them.
Where to check before you set off
Each river page shows the reading from the SPW station, refreshed every 15 minutes, with the allowed or forbidden status:
- Semois, navigable from 2.2 to 50 m³/s
- Lesse, from 1.5 to 52 m³/s
- Ourthe, from 2.5 to 65 m³/s
- Amblève, from 1 to 21 m³/s
Ready to go? See the Semois route or the Lesse to Dinant trip.