Mayflies
Caddisflies
A scenic Winneshiek County creek near Decorah with healthy populations of both wild browns and rainbows in cold spring water — the name is, once again, a fair description.
- Limestone
Rules at a glance
- Free fishing
- Fly only
Water temperature for Rainbow Trout
Ideal17°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
Good — water temperature is working for you, but time of day is the limiting factor today.
Likely species
Mayflies
Caddisflies
- Little Black Caddis (East)Most likelyLower confidenceNearest relative#16–18–20 · Adult
- Green Caddis / Rock WormAlso possibleLower confidence#14 · Adult
- Tan Caddis / Spotted SedgeAlso possibleLower confidenceNearest relative#14–16 · Adult
- October CaddisAlso possibleLower confidenceNearest relative#6–8–10 · Adult
Hatch timeline · todayPeak at 7am
12pm(now) — Grasshopper (Eastern)
Stage: Terrestrials on topApproach: Dry flyActivity: 75%
Also:Reed Smut64%Trico (Eastern)47%
Peak emergence windowWeather boostEmergence building5 food groups active
Peak activity at 7am — Trico (Eastern) (Trico (Eastern), Degree-days at peak)
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 with Pro.
Start free trial14-day free trial. Cancel anytime.
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
SulphurHatch
2
3
2
Trico (Eastern)Hatch
2
3
3
2
Eastern Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Eastern Summer BWO (Drunella)Hatch
2
3
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Local fly shops: Driftless Fly Fishing Co.
Permits & access
Permit required — see local rules.
- Iowa DNR — verify regulations.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 1
Terrain map
About this water
Water quality · US Clean Water Act
- Aquatic life: Supporting
- Recreation: Impaired
What this classification means
Recreation: Bacteria/pathogen advisory — mind wading cuts and immersion.
EPA ATTAINS assessment unit 'Coldwater Creek' (IA 01-UIA-280), 2024 Integrated Report. Aquatic Life use: Fully Supporting. Listed impairment causes: Pathogens. 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) · IA 01-UIA-280
The full read · show the working · for Rainbow Trout · confidence 75%
How the 77 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time40 × 13%5.2
Pressure75 × 7%5.3
Insect activity50 × 12%6.0
Conditions total= 77
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via South Branch Root Riverproxy
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout Open all year → Open all year
Related guides
Booking & contacts
Coldwater Creek
A scenic Winneshiek County creek near Decorah with healthy populations of both wild browns and rainbows in cold spring water — the name is, once again, a fair description.
Water temperature for Rainbow Trout
Ideal17°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
Good — water temperature is working for you, but time of day is the limiting factor today.
Likely species
Mayflies
Caddisflies
- Little Black Caddis (East)Most likelyLower confidenceNearest relative#16–18–20 · Adult
- Green Caddis / Rock WormAlso possibleLower confidence#14 · Adult
- Tan Caddis / Spotted SedgeAlso possibleLower confidenceNearest relative#14–16 · Adult
- October CaddisAlso possibleLower confidenceNearest relative#6–8–10 · Adult
Hatch timeline · todayPeak at 7am
12pm(now) — Grasshopper (Eastern)
Stage: Terrestrials on topApproach: Dry flyActivity: 75%
Also:Reed Smut64%Trico (Eastern)47%
Peak emergence windowWeather boostEmergence building5 food groups active
Peak activity at 7am — Trico (Eastern) (Trico (Eastern), Degree-days at peak)
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 2 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey(1)
Hatch predictions
Top prey shown — see all 4 with Pro.
Start free trial14-day free trial. Cancel anytime.
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
SulphurHatch
2
3
2
Trico (Eastern)Hatch
2
3
3
2
Eastern Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Eastern Summer BWO (Drunella)Hatch
2
3
3
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Local fly shops: Driftless Fly Fishing Co.
Permits & access
Permit required — see local rules.
- Iowa DNR — verify regulations.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 1
Terrain map
About this water
A scenic Winneshiek County creek near Decorah with healthy populations of both wild browns and rainbows in cold spring water — the name is, once again, a fair description.
- Limestone
Water quality · US Clean Water Act
- Aquatic life: Supporting
- Recreation: Impaired
What this classification means
Recreation: Bacteria/pathogen advisory — mind wading cuts and immersion.
EPA ATTAINS assessment unit 'Coldwater Creek' (IA 01-UIA-280), 2024 Integrated Report. Aquatic Life use: Fully Supporting. Listed impairment causes: Pathogens. 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) · IA 01-UIA-280
The full read · show the working · for Rainbow Trout · confidence 75%
How the 77 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time40 × 13%5.2
Pressure75 × 7%5.3
Insect activity50 × 12%6.0
Conditions total= 77
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via South Branch Root Riverproxy
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout Open all year → Open all year
Related guides
Booking & contacts