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The tailwater below Green Mountain Reservoir is running stable and cold, with excellent clarity and deep, structured seams that hold consistent winter trout. Expect narrow but meaningful midday feeding windows, especially when sunlight finds its way into the canyon. This is classic Blue River winter tailwater fishing: precise, technical, demanding, and deeply rewarding.
Updated: December 10, 2025
The Blue River below Green Mountain is a winter stronghold when other freestones lock up. Cold bottom-release flows, clear water, and pocket-filled canyon structure give trout exactly what they need to sit tight and feed selectively. Think slow drifts, light weight, and tiny bugs. Heavy steps and rushed presentations will cost you fish.
This week's update focuses on the Blue River Green Mountain tailwater, one of the most consistent winter fisheries on the Western Slope. Trout are feeding deliberately on midges and small baetis, holding deep in troughs and soft seams, and rewarding anglers who approach with subtlety and patience.
Listen to the Audio Overview
Conditions Summary
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Flow: ~350 to 450 CFS below Green Mountain Reservoir, stable early-winter release
Water Temperature: Mid 30s to low 40s
Air Temperature: Mid 20s to upper 30s
Clarity: Very clear
Crowds: Light
Best Window: 11 a.m. to 3 p.m.
Fishing Type Focus: Winter nymphing with small midges and baetis
Weather
Expect cold canyon mornings, pockets of midday sun, and rapid cooling once shadows return. Highs in the upper 20s to high 30s with lows dipping into the teens. Light wind can affect drifts but also encourages midge movement. Midday warmth drives the only consistent feeding window.
Top Flies in Your Box This Week
- Black Beauty 20 to 24
- Zebra Midge (black or red) 20 to 22
- Mercury Midge 20 to 22
- RS2 (black or gray) 20 to 22
- WD-40 20 to 22
- Juju Baetis 20 to 22
- Small Pheasant Tail 18 to 20
- Scud (olive or gray) 14 to 18
Pro Rig of the Week: Green Mountain Deep Slot Rig
- Indicator: Small yarn or minimal air-lock
- Lead Fly: Small Pheasant Tail 18 to 20 or Scud 14 to 16
- Dropper: Black Beauty or Zebra Midge 20 to 22
- Weight: One small to medium split shot adjusted carefully
- Target Water: Deep canyon troughs, inside bends, and slow winter seams
Hatch Chart for December
| Bug Type | Size | Notes |
|---|---|---|
| Midges | 20 to 26 | Primary winter forage; trout feed almost entirely subsurface |
| Baetis nymphs | 20 to 22 | Active on cloudy warm afternoons |
| Scuds | 16 to 18 | Occasionally important in tailwater transitions |
| Winter stoneflies | 18 | Rare but possible in sunny microclimates |
Download the Blue River Hatch Chart.
Access Points
Blue River Below Green Mountain Dam ⭐⭐⭐⭐⭐
The premier tailwater stretch with deep seams, canyon structure, and consistent winter flows. Ideal for technical nymphing with small patterns.
Rating: Five gold stars
BLM Access – Canyon Stretch ⭐⭐⭐⭐☆
Mixed pocket water and longer troughs that hold trout during the coldest months. Less pressured than the dam section and excellent for mobile anglers.
Rating: Four gold stars
Confluence Area Downstream ⭐⭐⭐⭐☆
Where the river flattens and widens slightly, offering soft edges and slower winter lanes. Productive on days with light cloud cover.
Rating: Four gold stars
Stop Here After the River
Angry James Brewing Co. (Silverthorne)
A warm, relaxed local brewery perfect after a day in the cold canyon. Expect big mountain vibes, community tables, and comfort-focused après energy.
What to order: The Resolute IPA and the rotating food truck’s signature warm dish.
Local Regulations and Notes
- Watch for changing dam release flows before entering canyon water
- Shelf ice can form along shaded edges
- Wading is technical; use caution on slick canyon rock
- Keep distance from other anglers due to narrow channel geometry
Companion Article
Colorado Winter Trout Feeding Behavior in Clear, Low-Flow Rivers
FAQ
Q: Is the Blue River below Green Mountain Reservoir good in winter?
A: Yes. Stable tailwater flows make it one of the most reliable cold-season fisheries in Colorado.
Q: What flies catch the most fish here?
A: Small midges, baetis nymphs, and subtle emergers are the bread and butter.
Q: Do streamers work?
A: Occasionally. Small leeches can move fish in deep slots on overcast days.
Q: How technical is this section?
A: Very. Clear water and slow current require stealth and precision.
Q: What is the best time of day?
A: Midday, when sunlight and slight temperature bumps activate midges.
Q: Can I sight-fish?
A: Yes in many sections, but trout spook easily in winter clarity.
Q: Is the Blue River below Green Mountain good in winter?
A: Yes. It is one of the most consistent and least crowded winter tailwaters in Colorado.
Q: How technical is this stretch compared to Dillon Dam?
A: Slightly less pressured, but still technical. Depth control and drift quality matter.
Q: Are dry flies an option right now?
A: Rarely. Subsurface midge patterns dominate winter success.
Q: What leader and tippet setup works best?
A: Long leaders with 5X to the lead fly and 6X to the midge dropper.
Q: Do scuds matter here in winter?
A: Yes. Scuds are an important secondary food source in this tailwater.
Q: When does the bite shut down?
A: Typically mid-afternoon once shadows and colder air settle into the canyon.