Freestone · Granite · Morvan / Nièvre

Yonne (Upper, Morvan Headwaters)

Yonne (Upper, Morvan Headwaters) — Le pont Boffrand-Hupeau - Joigny
Contributor photo

Le pont Boffrand-Hupeau - Joigny

Zéphyrios (https://www.flickr.com/photos/147161025@N05) - CC0

The upper Yonne, before the Pannesière and Chaumeçon reservoirs and long before the broad navigable river of tourist Burgundy, is a proper Morvan trout stream.

Poor · Brown Trout
CDC Emerger · 16-18
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
90% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp22.9°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-18
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp22.9°C
ClarityClear
Weather29°C
WindW 11 km/h
Pressure1017 hPa
Rain · recent1.6 mm
Rain · ahead8.3 mm

No gauge on this water — readings are regional estimates from weather, not a live gauge.

Water temperature for brown trout
Warm — slow
23°C est.ideal 1016°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 22.9°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

Hatch predictions

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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 · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Autumn OliveHatch
1
2
1
GrannomHatch
1
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.
  • AAPPMA Château-Chinon / Fédération de la Nièvre
  • 1ère catégorie standard.
What's coming
Plan ahead
5-day outlook
Water here around 23°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
  1. Yonne (Upper, Morvan Headwaters) — Le pont Boffrand-Hupeau - Joigny
    Le pont Boffrand-Hupeau - Joigny
  2. Terrain map of the venue
    Terrain map
About this water

The upper Yonne, before the Pannesière and Chaumeçon reservoirs and long before the broad navigable river of tourist Burgundy, is a proper Morvan trout stream. It rises in the Mont Preneley bogs at the heart of the granite massif and runs down through the high Morvan woods towards Château-Chinon. The first thirty kilometres are small, cold, and stony — real wild trout country that happens to share its name with a river everyone thinks they already know. Fish it slowly. The Baetis are good from late March onwards, the caddis build from May, and the stoneflies in the rough water are worth imitating through spring. The trout are wild and small-to-medium — six to ten inches is the working average, with the odd surprise in the deeper pool-tails that you did not expect. Upper Morvan water runs cold until May, so the season starts slowly. Nymph in April, shift to dry fly once the first march browns show, and do not expect a river that looks anything like the Yonne of the schoolbook maps. This is a different animal altogether — honest, quiet, and almost entirely unpublicised.

  • Granite
Water quality (WFD)
  • EcologyHigh
  • ChemicalFailing to achieve good
What this classification means

WFD ecological status Good → High and chemical status Good → Failing to achieve good corrected to EEA WISE 2022 (3rd RBMP) classification for waterbody FRHR42A (was a stale earlier-cycle value). Source: EEA WISE SWB_SurfaceWaterBody (discodata.eea.europa.eu), verified 2026-06-18.

WFD classification · FRHR42A

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
Clarity95 × 18%17.1
Feeding Time75 × 13%9.8
Pressure80 × 7%5.6
Insect activity48 × 12%5.8
Limiting factor: Water temperature (22.9°C) is outside Brown Trout's preferred range (10–16°C)= 57
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
Seasons & zones
  • Trout2nd Saturday of March → 3rd Sunday of September
Related guides
Booking & contacts