In this report
107 CFS in August — a Low-Water Alert and a Tactical Shift
At 107 CFS, the Pueblo tailwater is running below the threshold where summer trout thrive. This is not a comfortable flow for fish in hot weather, and it’s not the kind of low that fishes well on this dam-release system. The water will warm fast in the thin channels, and the trout will spend the hottest hours bunched in whatever deep, cool holding water they can find. Check the live flow chart before you drive down — 107 today may not be what you find when you arrive, and even a 30-CFS swing changes the game on a system this volatile.
What matters most this week: fish early, fish cool water, fish small and precise, and watch your thermometer.
Water Temp and Fish Welfare — Lead with This
Carry a thermometer. At 107 CFS in August, the shallower flats and the sun-exposed runs will climb into the mid-60s°F by late morning, and that’s when the trout shut down and stress. Your window is dawn through roughly 10:00 a.m., and again in the last couple of hours before dark. If the water hits 65°F, move to the deepest slots and the longest, slowest pools where groundwater chill holds the coldest refuge. If it climbs past that, stop. A stressed trout hooked and played in warm, thin water is a trout you may not put back alive, and the Pueblo tailwater’s summer health depends on anglers respecting that boundary.
What’s Hatching — Midges and Midge-Sized Mayflies
August on the Pueblo is a midge-dominant season, full stop. The year-round staple — Black Beauty, Mercury Midge, zebra midge, RS2 emergers in #20–24 — is your bread and butter. Tricos (#20–24) will show in scattered spinner falls in early morning, but they’ll be thin; don’t wait for them. Afternoon caddis (#16–18) can appear in the slower water as the day cools, but it won’t be a blitz, and at this low flow the fish are already exhausted from the heat.
The real player is the midge. Midges hatch all day on a tailwater — quietly, consistently, in the film and just below — and on a system this cold and clear, a #22 RS2 emerger or a small midge pupa will out-fish the larger patterns. At 107 CFS, the water is gin-clear, which means the trout can see your tippet from a mile away. Respect that.
Terrestrials — ants, beetles, hoppers — can work on a warm afternoon, but they’ll only shine during the tiny window when fish are actively feeding in the upper water column. In this flow and heat, terrestrials are a desperation play, not a primary tactic.
Rigging for Low, Clear Water
Your leader needs to be long, thin, and honest. Start with a 9-foot leader to 6X or 7X tippet. The trout are spooky and the water is transparent; you want every ounce of invisibility you can get. At 107 CFS, the deep slots are your only real holding habitat, and you’re going to need to get your flies down without heavy obvious rigs.
Best setup: A weighted midge pupa (#22 RS2 or Barr’s Black Beauty) as your point fly, fished 18 to 24 inches below a small indicator or fished tight-line. If you go the indicator route, use a small one (euro-style pencil indicator or a pinch of yarn) — big bobbers spook fish in clear water. Tight-line nymphing is often better on this water anyway; it lets you feel the take on a light fly and adjust on the fly.
Carry split shot in the smallest sizes. You’re not trying to slam the bottom; you’re trying to tick it occasionally and work the fly just off the substrate where the current is slowest. A single BB or two 000s placed 12 inches above the fly will get you there without deadening the drift or dragging bottom constantly.
If the afternoon warms and the caddis hatch actually shows, keep a #18 tan or olive caddis dry on a second rod or readily available — but don’t chase it if you’re not seeing consistent risers in the deeper, cooler runs. In this heat, surface activity will be sparse.
Where to Fish This Week
Forget the thin, exposed flats and the runs that get direct sun. The trout aren’t there at midday. Focus on the deep slots — the longer, slower pockets where the water depth shields the trout from temperature swing and where the current is gentle enough that a midge pupa doesn’t need a ton of drift to look natural. These are typically found where the river bends or narrows, or just downstream of obstructions that break the force of the release. On a tailwater this size, these slots are your entire productive zone in August low water.
The slower pools — the broad, deep flats where the current almost stalls — are less likely to hold concentrations than the small, defined slots, but they’re worth a drift on the midge pupa. The key is depth: if you can’t reach 3–4 feet, move on.
Avoid the bright, shallow tail-outs unless you’re fishing the first 30 minutes of legal light.
A Note on Access and Stewardship
The Pueblo tailwater is a special-regulation tailwater and heavily used. At low flows, trout are already stressed by heat and crowding. If you hook a fish, play it quickly and handle it carefully — wet your hands, keep it in the water, and don’t handle it at all if you can avoid it. If the water genuinely hits 66–67°F, call it and come back in the evening or wait for a cool spell and higher flow.
This week is a grind. The flow is marginal and the heat is against you. Your reward is solitude, clear water, and the chance to test your finesse skills on a river that demands them. Come early, fish small, and leave enough to live.