Freestone · Mixed · Navarra, ES

Río Ulzama

Trinidad de Arre

A major Arga tributary flowing from mixed granite-limestone Sierra de Aralar north to Pamplona.

Today · Closed season
Pheasant Tail Nymph (sz 18)
Forecast · Today
Closed season
Out of season. Try elsewhere.
75% projected
Today's fly
Pheasant Tail Nymph (sz 18)
Pheasant Tail Nymph (sz 18)
Conditions on the water · Today
Live gauge
Level
Falling
0.14 m
Dropping after lift
Water temp15.4°C
ClarityClearing
Weather13°C
WindN 19 km/h
Pressure1028 hPa
Rain · recent0.2 mm
Rain · ahead3.0 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Ideal
15°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 19°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 3pm

12pm(now) — Black Gnat

Stage: On emergersApproach: Emerger or dryActivity: 43%
Also:Small Dark Olive21%
Peak emergence window6 food groups active

Peak activity at 3pm — Small Dark Olive (Small Dark Olive, 9 food groups active)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds as a supporter.

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Evidence
Survey-backed · regionalHigh confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · October highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
1
Daddy Long LegsHatch
2
3
2
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
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.
  • Gobierno de Navarra fishing licence required
  • The Ulzama is one of the easier day-trip trout options from Pamplona, but the exact tramo and permit logic still needs checking before travel.
What's coming
Plan ahead
5-day outlook
Water here around 19°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. Trinidad de Arre
  2. Terrain map of the venue
    Terrain map
About this water

A major Arga tributary flowing from mixed granite-limestone Sierra de Aralar north to Pamplona. Accessible from the city, offering excellent upper and middle trout water — limestone gorges alternate with open pastoral valleys. Brown trout throughout; trout in lower sections after spates. Fast snowmelt response with consistent summer base flow. Technical nymphing and dry fly in gorges; pool-and-run fishing in valleys. Popular weekend escape from the city.

  • Mixed
Water quality (WFD)
  • Ecology: Good
  • Chemical: Unknown

WFD classification · ES091MSPF544

The full read · show the working · for Brown Trout · confidence 80%
How the 0 is built — score × weight = contribution
Temperature24 × 28%6.7
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time75 × 13%9.8
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Limiting factor: Water temperature (19°C) is outside Brown Trout's preferred range (10–16°C)= 65
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 May → 30 June

    RSS Arga–Ultzama basin (922 permits in 2026). All catch-and-release. Extendable to 15 Jul by resolution. Daily basin permit required. Most accessible day-trip trout water from Pamplona.

Related guides
Pyrenees PlaybookSpanish riversEuro Nymphingsubsurface methods
Booking & contacts