Karst Spring · Limestone · Karlovac County / Risnjak NP

Kupa (Risnjak National Park)

Risnjak National Park venue image
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The Kupa rises as a powerful karst spring at the foot of Risnjak mountain near Razloge — one of the classic Dinaric karst spring rivers.

Poor · Brown Trout
CDC Emerger · 16-20
Poorlive now
Not the day for it
River dropping into shape after a lift. Take your time — read the water before you cast.
90% confidence
What moved it
  • LevelProxyvia River Kolpa
  • Water temp23.0°C
  • ClarityUnfishableColouring up
Today’s fly
CDC Emerger
CDC Emerger16-20
Proven pattern for this period
Conditions on the water
Proxy gauge
Level
Falling
Proxy
via River Kolpa
Water temp23.0°C
ClarityUnfishable
Weather20°C
WindNE 8 km/h
Pressure1018 hPa
Rain · recent5.5 mm
Rain · ahead1.5 mm

No gauge on this water — conditions are inferred from River Kolpa. The trend transfers, the absolute level does not.

Water temperature for brown trout
Warm — slow
23°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.
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 2 active hatches hour by hour with Pro.

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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
Brown SedgeHatch
2
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Blue Winged OliveHatch
2
3
3
3
3
2
Mayfly (Green Drake)Hatch
2
2

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.
  • Croatian freshwater fishing licence required
  • Risnjak NP permit required for the source area
  • Check Croatian Angling Federation for beat permits.
What's coming
Plan ahead
5-day outlook
Water here around 23°C. Nothing cooler within range — carry a thermometer.
Gallery · 1
  1. Terrain map of the venue
    Terrain map
About this water

The Kupa rises as a powerful karst spring at the foot of Risnjak mountain near Razloge — one of the classic Dinaric karst spring rivers. Cold, blue-green, emerald-clear limestone water with wild brown trout, grayling, and hucho in the deeper holding pools. The source reach in Risnjak NP is among the finest wild-trout water in Croatia.

  • Limestone
The full read · show the working · for brown trout · confidence 90%
How the 0 is built — score × weight = contribution
Temperature2 × 28%0.6
Flow80 × 22%17.6
Clarity0 × 18%0.0
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity43 × 12%5.2
Limiting factor: Water is unfishable — too coloured for Brown Trout= 39
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via River Kolpaproxy
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.
A drop and clear would lift the flow and clarity scores.
Related guides
Hucho / Danube Salmonspecialist apex-predator guideGrayling Playbookgrayling tacticsEuro Nymphingsubsurface methods
Booking & contacts