Freestone · Mixed · Haute-Savoie

Nom

A rushing forest river, the Nom, flowing over rocks and fallen branches through golden autumn trees near Thones, Haute-Savoie, France.
Marginal · Brown Trout
Small Perdigón · 16-20
New ruleReported 1 Aug 2026

Severe drought restrictions (alerte renforcée) in force

The Arve aval zone (Dept 74) is at alerte renforcée — the second-highest French drought tier — under a préfectoral arrêté. Fishing itself is not named as prohibited, but water is severely restricted and flows are likely very low; fish with care and check locally.

Arrêté préfectoral n°37507 ↗

Temporary notices from official orders and recent fishery reports — they clear automatically once out of date. Always confirm locally before travelling.

Marginallive now
Slow going — pick your moments
River temperature is the limiting factor today, not the flow. Fish dawn or dusk if you go at all, and handle everything with extra care.
80% confidence
What moved it
  • LevelProxyvia Borne
  • Water temp19.6°C
  • ClarityVery colouredColouring up
Today's fly
Small Perdigón
Small Perdigón16-20
Euro-nymph
Conditions on the water
Proxy gauge
Level
Rising
Proxy
via Borne
Water temp19.6°C
ClarityVery coloured
Weather22°C
WindSE 7 km/h
Pressure1019 hPa
Rain · recent0.0 mm
Rain · ahead5.3 mm

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

Water temperature for Brown Trout
Warm — slow
20°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 19.6°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 6pm

Hatch predictions

Today's headline hatch shown — see all 9 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
Survey-backed · regionalModerate confidence

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

Through the year
0–3 scale · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout 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
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here around 20°C — probably warm enough to stress Brown Trout . These are likely cooler.
Borne
20 km
~16°C
Brown trout · Grayling
Gallery · 2
  1. A rushing forest river, the Nom, flowing over rocks and fallen branches through golden autumn trees near Thones, Haute-Savoie, France.
    Le Nom @ Circuit Jean-Jacques Rousseau @ Thones
  2. Terrain map of the venue
    Terrain map
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Unknown
What this classification means

WFD ecological status Good → Moderate corrected to EEA WISE 2022 (3rd RBMP) classification for waterbody FRDR539B (was a stale earlier-cycle value). Source: EEA WISE SWB_SurfaceWaterBody (discodata.eea.europa.eu), verified 2026-06-18.

WFD classification · FRDR539B

The full read · show the working · for Brown Trout · confidence 80%
How the 30 is built — score × weight = contribution
Temperature30 × 28%8.4
Flow55 × 22%12.1
Clarity15 × 18%2.7
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity51 × 12%6.1
Limiting factor: Water is very coloured — too coloured for Brown Trout= 45
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Borneproxy
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.
A drop and clear would lift the flow and clarity scores.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 2nd Saturday of March → 3rd Sunday of September
Related guides
Pyrenees PlaybookFrench riversEuro Nymphingsubsurface methods
Booking & contacts
Clubs & associations