Freestone · Mixed · Colorado

Boulder Creek (Boulder Canyon)

Boulder Creek flowing swiftly through a rocky canyon lined with pine trees and granite boulders in Boulder Canyon, Colorado.

Boulder Creek up in Boulder Canyon is the quintessential Front Range small-water quick-hit — a tumbling little freestone right beside CO-119 that holds eager browns and rainbows and asks nothing more than a short cast and a willingness to scramble.

Poor · Rainbow Trout
Parachute Adams · 12-18
Poorlive now
Not the day for it
River high but settled. Not much stacked in your favour today. Worth an hour if you are nearby, not worth the special trip.
90% confidence
What moved it
  • Level1.48 mLast reading 1h ago
  • Water temp22.9°C
  • ClarityClear
Today's fly
Parachute Adams
Parachute Adams12-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
1.48 m
Last reading 1h ago
Water temp22.9°C
ClarityClear
Weather30°C
WindE 12 km/h
Pressure1011 hPa
Rain · recent0.0 mm
Rain · ahead1.6 mm

Live readings — water temperature is an estimate where the gauge does not record it.

Water temperature for Rainbow Trout
Warm — slow
23°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 22.9°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Hatch timeline · todayQuiet day

Hatch predictions

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Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 3 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water 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
2
2
2
2
2
1
Western Green DrakeHatch
2
2
Flav (Small Western Green Drake)Hatch
2
3
2
Mahogany DunHatch
2
2
American March BrownHatch
2
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.
  • Colorado licence
  • Wild Trout special-regulation section in Boulder Canyon — verify CPW rules.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Probably above the Rainbow Trout safety line — these are likely cooler, but carry a thermometer.
Big Thompson River (canyon, below Lake Estes)
46 km
~10°C
Brown trout · Rainbow trout
Gallery · 2
  1. Boulder Creek flowing swiftly through a rocky canyon lined with pine trees and granite boulders in Boulder Canyon, Colorado.
    Boulder Creek, Boulder Canyon
  2. Terrain map of the venue
    Terrain map
About this water

Boulder Creek up in Boulder Canyon is the quintessential Front Range small-water quick-hit — a tumbling little freestone right beside CO-119 that holds eager browns and rainbows and asks nothing more than a short cast and a willingness to scramble. It's small enough to wade in tennis shoes and flashy enough to muddy up after a storm, with a Wild Trout section in the canyon for those who want to keep it honest. Nobody's driving across the state for it, but for an after-work hour out of Boulder it's hard to beat, and the upper canyon thins the crowd nicely.

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

EPA ATTAINS assessment unit 'Boulder Creek, mainstem and tributaries.' (COSPBO02b_G), 2024 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Metals Other Than 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) · COSPBO02b_G

The full read · show the working · for Rainbow Trout · confidence 90%
How the 6 is built — score × weight = contribution
Temperature3 × 28%0.8
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time45 × 13%5.9
Pressure75 × 7%5.3
Insect activity54 × 12%6.5
Limiting factor: Water temperature (22.9°C) is outside Rainbow Trout's preferred range (10–18°C)= 51
Can you trust it?
Water temperatureair-to-water estimateestimated
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
  • Trout1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Booking & contacts