Border river with huchen, grayling, and brown trout, warm limestone karst character. A southern Alpine experience on a river shared between nations.
- River
- Limestone
Water temperature for brown trout
Warm — slow23.0°Cideal 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
⛔ Water at 23°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayQuiet day
Hatch predictions
Today's headline hatch shown — see all 4 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
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
1
2
2
2
2
2
1
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Alpine RhithrogenaHatch
1
2
2
1
Large Dark OliveHatch
1
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
- Fishing licence + permit
- Shared with Croatia.
What's coming
Plan ahead
5-day outlook
Water here at 23.0°C. Nothing cooler within range.
Gallery · 6
The Kolpa's clear water 
The Kolpa in its gorge 
Boulders on the Kolpa 
The Kolpa at Primostek 
Canoe on the Kolpa Terrain map
About this water
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · SI21VT50
The full read · show the working · for brown trout · confidence 90%
How the 4 is built — score × weight = contribution
Temperature2 × 28%0.6
Flow80 × 22%17.6
Clarity75 × 18%13.5
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity45 × 12%5.4
Limiting factor: Water temperature (23°C) is outside Brown Trout's preferred range (10–16°C)= 53
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
Directions
Seasons & zones
- Trout1 March → 30 September
- Grayling16 May → 30 November
- Hucho1 October → 14 February
Related guides
Booking & contacts
River Kolpa
Contributor photo
The Kolpa's clear water
Klemen Čotar - CC BY-SA 4.0
Border river with huchen, grayling, and brown trout, warm limestone karst character.
Water temperature for brown trout
Warm — slow23.0°Cideal 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
⛔ Water at 23°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayQuiet day
Hatch predictions
Today's headline hatch shown — see all 4 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
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
1
2
2
2
2
2
1
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Alpine RhithrogenaHatch
1
2
2
1
Large Dark OliveHatch
1
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
- Fishing licence + permit
- Shared with Croatia.
What's coming
Plan ahead
5-day outlook
Water here at 23.0°C. Nothing cooler within range.
Gallery · 6
The Kolpa's clear water The Kolpa in its gorge Boulders on the Kolpa The Kolpa at Primostek Canoe on the Kolpa Terrain map
About this water
Border river with huchen, grayling, and brown trout, warm limestone karst character. A southern Alpine experience on a river shared between nations.
- River
- Limestone
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · SI21VT50
The full read · show the working · for brown trout · confidence 90%
How the 4 is built — score × weight = contribution
Temperature2 × 28%0.6
Flow80 × 22%17.6
Clarity75 × 18%13.5
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity45 × 12%5.4
Limiting factor: Water temperature (23°C) is outside Brown Trout's preferred range (10–16°C)= 53
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
Directions
Seasons & zones
- Trout1 March → 30 September
- Grayling16 May → 30 November
- Hucho1 October → 14 February
Related guides
Booking & contacts