In this report
107 CFS and a Cool Advantage — Early Fall on the Pueblo Tailwater
We’re sitting at 107 CFS on the gauge right now, and that’s genuinely good news for September on this water. Here’s why it matters: the Pueblo tailwater doesn’t follow the same seasonal logic as a freestone. In summer, low flow is a water-temperature curse — thin water heats fast in the sun, and trout get stressed. But we’re past that danger zone. At 57°F, the water is already cooling into fall, and at this flow you’ve got stable, cold conditions that will only get better. The dam is releasing enough to keep the channel moving and maintaining good oxygenation without the volatility that hammers this tailwater in other seasons. Before you drive down, check the flow chart — these releases can swing — but if it’s still in this ballpark, you’re looking at a genuinely fishable window.
The wading is manageable at 107. You won’t be stumbling through waist-deep channels; you’ll be picking your way through thigh-deep to knee-deep water in most of the main current. The key is feeling for the deep slots and the inside bends where browns and rainbows hold in cooler water, especially as the day warms slightly in afternoon. Early morning and dusk are prime, but unlike mid-summer, you don’t have to abandon the river at 11 a.m. — the water temperature is in your favor.
Baetis and Midges Driving the Menu
September on this tailwater brings back the small mayflies. Baetis (fall blue-winged olives) are the seasonal mainstay — look for #20–22 emergers and dries on overcast afternoons, particularly around mid-day when cloud cover keeps light low and water temperature stable. They’re not a blizzard like a spring hatch; they’re a steady, reliable presence that will produce fish if you’re watching the water and matching the size.
But do not sleep on midges. They’re the year-round foundation of this tailwater, and September is no exception. Black Beauty, Mercury Midge, and zebra midges in #20–24 will catch fish every single day, in every condition, whether there’s a visible hatch or not. These aren’t backup flies — on the Pueblo tailwater, midge nymphs are often the call, especially in the first few hours after dawn and in the slower, deeper holding water where big browns hunt.
Terrestrials are still worth a cast too. An ant or small hopper in #16–18 can bring up a careless fish in the afternoon, but don’t bank on it — it’s a bonus, not a primary plan.
How to Rig and Fish This Week
The dropper setup: Start with a heavier anchor — a Barr’s-style Tungsten or similar #18–20 nymph, something that will tick bottom without constant adjustment. Tie 18 to 20 inches of 5X tippet below that, then attach a #20–22 midge emerger (RS2, Barr’s Emerger, or similar) as your dropper. This lets you fish two depth zones at once: the heavy nymph touching substrate in the deep slots, the emerger suspended just off bottom where Baetis and more actively feeding trout often intercept.
If you’re not getting consistent bottom contact, add a small split shot — not above the dropper, but right at the base of your tippet where the dropper knot sits. That keeps your presentation clean and your bottom-feeding fly in the zone without overweighting the rig.
Indicator vs. tight-line: At 107 CFS, a small strike indicator (pencil-thin, about 12 to 15 feet up from your flies) gives you feedback in slower glides and around the inside bends. If you’re fishing faster current or tight against a bank, tight-lining with your rod tip high and a slight mend every few seconds works beautifully — you’ll feel takes more directly, and you’ll stay in contact with the bottom.
Tippet and leader: 5X is your workorse — it’s fine enough to get a natural drift through gin-clear tailwater water (and at 107, the water is transparent), but stout enough to handle the browns that live here. Drop to 6X only if you’re seeing refusal on smaller flies; this water can demand it on slow, overcast days, but 5X covers most scenarios.
Where to spend your time: Fish the deep, cool slots — the inside bends where the current slows, the pocket water behind mid-channel rocks, and the slightly deeper flats immediately downstream of faster runs. Avoid the thin, bright water over light gravel; the fish have moved to deeper, shadier lies as the season shifts. Early in the day, focus on the deeper runs that intercept dawn insects. As the sun climbs and the afternoon BWO hatch window opens (usually around 1 to 3 p.m.), switch to slower, shallower edges where drifting emergers will be more visible to feeding trout.
Water Temperature and Fish Welfare
Carry a thermometer. At 57°F, we’re in good shape, but September can still warm quickly on a clear afternoon, especially if flows drop further. If the water edges toward the low 60s (62–63°F), shift your effort to the early morning, the later evening, and the deepest, shadiest water. Midges will still work in the afternoon heat, but don’t spend hours targeting rising fish in thin, sunlit water once the water temperature climbs — give the trout a break and let them recover in cool, deep holding lies.
Before You Drive Down
The Pueblo tailwater’s flows are dam-driven and can swing dramatically week to week. Check the gauge before you leave — if it’s dropped below 70 or climbed above 300, your water-type and wading strategy will shift. At 107, you’re looking at a stable, fishable window, but that can change. A quick look takes 30 seconds and saves a wasted drive.