Freestone · Limestone · Jura

Héria

Héria terrain map
Terrain map

The Héria is classic Jura water on a small scale: a limestone stream with the clarity and temperature stability of a proper chalk river, where the trout live long enough to learn every fly in the box and are perfectly happy to show you they've done so.

Poor · Brown Trout
CDC Emerger · 16-20
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 temp22.0°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-20
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp22.0°C
ClarityClear
Weather21°C
WindE 10 km/h
Pressure1016 hPa
Rain · recent0.0 mm
Rain · ahead11.3 mm

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

Water temperature for brown trout
Warm — slow
22°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°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayQuiet day

Hatch predictions

See the full hour-by-hour hatch timeline with Pro.

Start free trial

14-day free trial. Cancel anytime.

Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

Start free trial

14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

Start free trial

14-day free trial. Cancel anytime.

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
GrannomHatch
2
2
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
1

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Gammarus Scud (Olive)
Gammarus Scud (Olive)
12-16 · Gammarus Scud
Dead-drift, sub-surface
What's coming
Plan ahead
5-day outlook
Water here around 22°C. Nothing cooler within range — carry a thermometer.
About this water

The Héria is classic Jura water on a small scale: a limestone stream with the clarity and temperature stability of a proper chalk river, where the trout live long enough to learn every fly in the box and are perfectly happy to show you they've done so. The fish are wild, the water is transparent, and the upstream dry-fly drill is the only way to fish it with any self-respect. Work upstream in short, precise casts, keep out of the water when you can, and treat every presentation as if it's your only one. Olives in spring, caddis through June and July, terrestrials in the low water of late summer. This is not a numbers river. It's a river where you go home remembering three fish in detail because each of them required something specific from you.

  • Limestone
Water quality (WFD)
  • EcologyGood
  • ChemicalUnknown

WFD classification · FRDR11905

The full read · show the working · for brown trout · confidence 90%
How the 12 is built — score × weight = contribution
Temperature6 × 28%1.7
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity45 × 12%5.4
Limiting factor: Water temperature (22°C) is outside Brown Trout's preferred range (10–16°C)= 48
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.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
  • Trout2nd Saturday of March → 3rd Sunday of September
Related guides
Booking & contacts