Tailwater · Mixed · Northern California, US

Lower Stanislaus River

Lower Stanislaus River terrain map

Cold foothill tailwater below Goodwin Dam, which is itself a regulating afterbay for big New Melones up the canyon — so the flow you get at Knights Ferry is whatever the Bureau decides, not what the sky does.

Tomorrow · Slow going — pick your moments
Sowbug
Forecast · Tomorrow
Slow going — pick your moments
Slow going — pick your moments and do not force it.
90% projected
Today's fly
Sowbug
Sowbug
Conditions on the water · Tomorrow
Live gauge
Level
Steady
11.54 m
Water temp18.5°C
ClarityClear
Weather21°C
WindN 16 km/h
Pressure1015 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

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

Water temperature for Rainbow Trout
Warm — slow
19°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow 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 20.7°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Mayflies
Caddisflies
terrestrials
Hatch timeline · tomorrowPeak at 5pm

12pm(now) — Flying Ants

Stage: Terrestrials on topApproach: Dry flyActivity: 51%
Also:Trico41%Reed Smut29%
Peak emergence windowWeather boost4 food groups active

Peak activity at 5pm — Summer River Midge (Summer River Midge, 3 food groups active)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 4 guilds with Pro.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 with Pro.

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Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
2
2
2
2
2
1
Western Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Pale Morning DunHatch
2
3
3
2
TricoHatch
2
3
2
Black MidgeHatch
2
3
3
3
3
3
3
3
3
3
3
2

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

Ranked for today
Rainbow Trout fly box
Permits & access
Permit required — see local rules.
  • Open all year; barbless, with low-flow / steelhead closures — check CDFW
  • ESA-listed steelhead present: handle with care
  • Flow tracks Goodwin/New Melones releases.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here at 20.7°C — the fishing's alive, but these are cooler if you'd rather rest the warm water.
Lower Mokelumne River
55 km
~12°C
Rainbow trout
About this water

Cold foothill tailwater below Goodwin Dam, which is itself a regulating afterbay for big New Melones up the canyon — so the flow you get at Knights Ferry is whatever the Bureau decides, not what the sky does. It holds wild rainbows along with an ESA-listed steelhead run, so those fish get named and left alone. Drift-boat and walk-in water over clean gravel: caddis and PMD through the warm months, blue-wings when it cools, and an egg bite behind the autumn salmon. Check the release before you load the boat, because the river answers to the dam.

  • Mixed
Conservation note

Holds ESA-listed Central Valley steelhead. We name their presence and leave it there — no catch score on listed fish, no targeting nudge. Handle any you meet with real care.

Water quality · US Clean Water Act
  • Aquatic life: Impaired
  • Fish consumption: Impaired
What this classification means

Fish consumption: Consumption advisory (Mercury) — fish for sport, not the table.

EPA ATTAINS assessment unit 'Stanislaus River, Lower' (CAR5353000019980817151834), 2024 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Temperature, Mercury. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · CAR5353000019980817151834

The full read · show the working · for Rainbow Trout · confidence 80%
How the 23 is built — score × weight = contribution
Temperature17 × 28%4.8
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time55 × 13%7.2
Pressure75 × 7%5.3
Insect activity34 × 12%4.1
Limiting factor: Water temperature (20.7°C) is outside Rainbow Trout's preferred range (10–18°C)= 54
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–18 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Booking & contacts