Stillwater · Alluvial · Isère / Nord-Isère (Trept), FR

Domaine des 3 Lacs du Soleil

Domaine des 3 Lacs du Soleil terrain map

The Domaine des 3 Lacs du Soleil is a private three-lake complex at Trept in the Nord-Isère, about an hour from Lyon, and the Grand Lac is the fly-only reservoir — the other two waters are for bait and coarse fishing and are not what a fly angler comes here for.

Fair · Rainbow
Medium nymphs · 14–16
New ruleReported 20 Aug 2026

Severe drought restrictions (alerte renforcée) in force

VigiEau lists this venue's surface-water zone (Bourbre, dépt 38) at alerte renforcée, under an official préfectoral drought arrêté. Fishing is not itself banned by it, but water levels are low — go gently on stressed fish.

Arrêté préfectoral n°37806 ↗

Temporary notices from official orders and recent fishery reports — they clear automatically once out of date.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

Fairlive now
Reasonable autumn fishing likely at Domaine des 3 Lacs du Soleil
Water temperature is the limiting factor today, not the wave. Fish dawn or dusk if you go at all, and handle everything with extra care.
59% confidence

Domaine des 3 Lacs du Soleil is often best in spring through autumn.

What moved it
  • WindSE 19 km/hGentle breeze
Today's fly
MN
Medium nymphs14–16
Search the runs and pockets, dead-drift near the bottom.
Conditions on the water
Estimate
Wind
Gentle breeze
SE 19 km/h
N
SE
from the south-east
Wave40 cm chop
Water temp19.0°C
Air temp20°C
CloudOvercast
Pressure1020 hPa
Rain · recent0.0 mm

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

How to fish it · for Rainbow
When
March–May and September–October
Where
Start with Medium nymphs (12-14) on a slow, natural presentation — check locally for the preferred method. Rainbows respond to more active retrieves — try short strips between pauses. If that does not produce, switch depth or speed before changing the pattern entirely.
The plan
Plan A

Start with Medium nymphs (12-14) on a slow, natural presentation — check locally for the preferred method. Rainbows respond to more active retrieves — try short strips between pauses. If that does not produce, switch depth or speed before changing the pattern entirely.

Plan B

A fry-imitating pattern stripped through the margins can save a blank in autumn.

Watch for

Keep an eye on changing conditions — wind shifts and cloud breaks can trigger short feeding spells.

Bank

Bank-only venue. Fish from accessible margins, points, weed edges, and inflows.

Sub-surface · on the nymphunder the surface

Hatch predictions

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

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 5 as a supporter.

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14-day free trial. Cancel anytime.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Black MidgeHatch
2
3
3
3
3
3
3
3
3
3
3
2
Reservoir BuzzerHatch
2
3
3
3
3
3
2
Lake OliveHatch
2
3
3
3
3
3
2
Silverhorns & LonghornsHatch
1
2
2
2
1

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

Ranked for today
Rainbow fly box

More balanced than the mountain-river pack. French nymphing still matters, but there is more room for dries, spiders and general searching flies.

MN
Medium nymphsTop
14–16 · Nymph
Search the runs and pockets, dead-drift near the bottom.
DR
dries
12–16 · Fly
A dependable searching pattern for these waters.
BU
buzzers
10–14 · Buzzer
Static or slow on a long leader — the staple stillwater chironomid.
ST
streamers
8–10 · Streamer
Strip it for fish chasing fry or in coloured water.
Permits & access
Permit required — see local rules.
  • Commercial fly-only on the Grand Lac (the other lakes are bait/coarse only)
  • Day tickets required
  • Black bass and perch no-kill.
What's coming
Plan ahead
5-day outlook
Condition match
49%
Cloud50%
Wind65%
Temp25%

Conditions are away from Domaine des 3 Lacs du Soleil's sweet spot — it usually fishes best in ripple wind with cloud skies.

Water here around 19°C. Nothing cooler within range — carry a thermometer.
About this water

The Domaine des 3 Lacs du Soleil is a private three-lake complex at Trept in the Nord-Isère, about an hour from Lyon, and the Grand Lac is the fly-only reservoir — the other two waters are for bait and coarse fishing and are not what a fly angler comes here for. The Grand Lac is stocked with rainbow trout as the main target, with perch and black bass both present and both managed as no-kill, which is the sort of mature policy that used to be unheard of in French commercial fisheries and is now slowly becoming standard at the better venues. The water is alluvial and warms up in summer more than an upland reservoir does, so the early season (March–May) and the autumn shoulder (September–October) are the productive windows. This is the closest serious fly-only commercial fishery to Lyon and it functions as the Rhône-Alpes equivalent of Coyolles: your reliable weekend casting venue when the rivers are out of shape.

  • Fishery
  • Alluvial
Why this score
  • autumn conditions with overcast skies and breezy wind.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout Year-round → Year-round
Related guides
Small Stillwater Playbookstillwater tacticsThermal Layers & Troutreading depth and temperaturePyrenees PlaybookFrench rivers
Booking & contacts
Permits & access
  • Commercial Trout Fishery
    Commercial managed trout fishery. Contact venue directly for day ticket availability and pricing.
  • Official website