Mayflies
Caddisflies
Gammarids
- Ecology: Moderate
- Chemical: Unknown
WFD classification · NL60_GEUL
Rules at a glance
- Permit required
Water temperature for Brown Trout
Warm — slow17°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.
Likely species
Caddisflies
- Large sedgesMost likelyNearest relative#8–10 · AdultBig waked sedge in the last light and after dark.
- Net-spinning caddisAlso possibleLower confidenceNearest relative#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- CapererAlso possibleLower confidence#10–12 · AdultBig autumn sedge; fish dry at last light.
- Green SedgeAlso possibleLower confidenceNearest relative#10–12–14–16 · NymphFree-living green caddis larva; fast stony riffles.
Hatch timeline · todayPeak at 17:00
Hatch predictions
Today's headline hatch shown — see all 12 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 3 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 as a supporter.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Fly box · Brown Trout
Permits & access
Permit required — see local rules.
- VISpas available to non-residents
- Can be purchased online or from tackle shops
- Valid for most affiliated waters nationwide.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
The Geul river near Valkenburg, Limburg Terrain map
Water quality (WFD)
The full read · show the working · for Brown Trout · confidence 90%
How the 0 is built — score × weight = contribution
Temperature73 × 28%20.4
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity76 × 12%9.1
Conditions total= 78
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Roerproxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 1 March → 30 September
Related guides
Booking & contacts
Geul
Water temperature for Brown Trout
Warm — slow17°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.
Likely species
Caddisflies
- Large sedgesMost likelyNearest relative#8–10 · AdultBig waked sedge in the last light and after dark.
- Net-spinning caddisAlso possibleLower confidenceNearest relative#12–14–16 · PupaWidespread riffle net-spinner; evening emergence.
- CapererAlso possibleLower confidence#10–12 · AdultBig autumn sedge; fish dry at last light.
- Green SedgeAlso possibleLower confidenceNearest relative#10–12–14–16 · NymphFree-living green caddis larva; fast stony riffles.
Hatch timeline · todayPeak at 17:00
Hatch predictions
Today's headline hatch shown — see all 12 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 3 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 as a supporter.
Start free trial14-day free trial. Cancel anytime.
Evidence
Survey-backed · regionalHigh confidence
Backed by regional invertebrate surveys; no sampling on this exact reach yet.
Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Fly box · Brown Trout
Permits & access
Permit required — see local rules.
- VISpas available to non-residents
- Can be purchased online or from tackle shops
- Valid for most affiliated waters nationwide.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 2
The Geul river near Valkenburg, Limburg Terrain map
Water quality (WFD)
- Ecology: Moderate
- Chemical: Unknown
WFD classification · NL60_GEUL
The full read · show the working · for Brown Trout · confidence 90%
How the 0 is built — score × weight = contribution
Temperature73 × 28%20.4
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity76 × 12%9.1
Conditions total= 78
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Roerproxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 1 March → 30 September
Related guides
Booking & contacts