In this report
42 CFS: Why This Week Demands Your Full Attention to Water Temperature
The gauge is reading 42 CFS right now, and that’s a hard stop for daytime fishing on the Pueblo tailwater. This isn’t winter—it’s July, the air is hot, and thin water in the heat is a trout-welfare problem, not a tactical puzzle to solve with better presentation.
Here’s what 42 means on this water: the river is running at the extreme low end of summer stress. Anything under 50 CFS in July puts brown and rainbow holding water at genuine risk of temperature climb. You need a thermometer in your pack this week, full stop. If the water hits the mid-60s°F, you’re done fishing. Even at 62–63°F, you’re in the zone where every catch and release adds measurable stress. Fish are concentrated in the deepest, coldest pockets—usually tight to the dam-adjacent slots or in the darker deeper runs below town—and they’re not forgiving of bad drifts or heavy-handed wading.
When to fish, and what that looks like: Dawn until roughly 10 a.m., and again from about 7 p.m. onward, are your windows. That’s not a suggestion; it’s the margin between decent conditions and genuinely harmful ones. In between, the sun heats the gin-clear water fast, and trout retreat to micro-refuges you’ll spook more often than not. Carry that thermometer. Check it every 30 minutes.
The Hatch Window: Midges All Day, Tricos at First Light, Caddis in the Evening
This water runs on the dam’s schedule, not the freestone calendar. July on the Pueblo tailwater means the midge hatch is your primary and almost constant resource—it’s the reliable foundation of the whole week.
Midges (#20–24): Black Beauty, Mercury Midge, zebra midge, and RS2 emergers dominate the drift. They’re hatching throughout the day, and they’re especially thick in the early morning and late evening. At 42 CFS, the water column is thin and compressed; every midge emergence is concentrated in a narrow band. Fish the emerger phase hard—the RS2 in olive or black, fished just below the film, draws takes all week long. In the nymph phase, a #22–24 Mercury Midge or zebra midge on the point, with 18–20 inches of tippet below, will tick the bottom of the deeper holding slots.
Trico spinners (first light, #20–24): The fall starts just after sunrise and lasts roughly 90 minutes. The spinners are small, thin-bodied, and the fish key on them hard in the slack water where spinners pile up—the inside of bends, the slow edges behind larger rocks, anywhere current slows. A #22 or #24 Trico spinner imitation (parachute or shuck, your choice) with a long fine tippet (7X, sometimes 8X) is the right call. This is the most consistent early bite of the week if you’re on the water before 7 a.m.
Caddis (evening, #16–18): Evening hatches are solid on this tailwater. A #16–18 tan or olive elk-hair caddis fished dry, or a soft-hackle caddis pupa as a dropper behind a smaller midge emerger, will produce in the last two hours of light. The hatch is not huge like a freestone spring emergence, but it’s predictable and fish respond. The evening also gives you the advantage of cooler water and less spooky trout.
Rigging for Gin-Clear, Concentrated Fish
At 42 CFS, the water reads like a creek. Every angler stands out, every sloppy cast shows, and every trout within 30 feet knows you’re there. Adjust accordingly.
Your primary rig this week:
- Point fly: #22–24 Mercury Midge or zebra midge (nymph), or #22 RS2 emerger if you’re fishing just below the surface.
- Dropper: #18–20 PMD emerger, or a #20 Trico nymph (gray or olive), suspended 18–20 inches above the point on 5X tippet.
- Tippet: 6X for the main leader (from your fly line to the point fly), then drop to 5X or even 6X for the dropper to keep it from fouling and to preserve visibility in clear water.
- Weight and depth: A single small split shot, pinched onto the 5X dropper tippet 12 inches up from the point fly, will keep you in the bottom 18 inches of the water column without snagging constantly. If the bottom is scattered rock or silt, you might not need any weight at all—let the flies dead-drift and tick the bottom with minimal resistance.
Indicator or tight-line? At this flow, tight-line nymphing wins. You’ll feel subtle takes better, you’ll stay in contact with the bottom more consistently, and you won’t telegraph your position with a large bobber in gin-clear water. Use a high-visibility sighter (neon orange or yellow 2X mono, about 12 inches long) as a reference point, but fish the actual drift feel-first.
Where to Spend Your Time
Forget the flats and skinny-water areas this week. The sun-exposed edges will warm fast, and fish won’t be there during the day regardless.
Deep slots and tailout pockets: The deepest runs, especially those with current breaks and darker bottom (silt or slab rock rather than light sand), hold the coldest water. Fish these areas with methodical, tight drifts. Let the nymphs sit in the slot for two or three seconds of the drift before lifting out. Takes often come as the flies are just beginning to swing.
Dam-adjacent water: The cold release comes straight from the dam, and some of the most consistent fish live in the first mile below. Access varies by current regulations, so verify before you head down, but this zone historically holds big browns and rainbows precisely because the water stays cold. Approach carefully and fish slowly.
Evening runs with visible current: As the sun drops and water temperature begins to fall, fish move back into areas they abandoned mid-day. The transition from 6 p.m. onward is often the most active window of the day. Runs with moderate current (not the slowest water, not the heaviest current) and some depth are your best bet.
One Critical Logistics Note
Before you drive down, check the flow chart on this page. 42 CFS is current as of writing, but this water swings hard and fast—releases can jump or plummet in hours. A spike to 200+ CFS is not unusual and would make wading dangerous and fishing nearly impossible. A drop below 30 CFS would compound the temperature problem even more. Real-time is your friend this week. If flows jump above 300 CFS, the river becomes a wade hazard and the hatches get disrupted.
Carry water, a hat, and sunscreen. Fish the cool hours. Use the thermometer. This week, you’re not chasing trophy numbers—you’re practicing stewardship on a water under stress. Do it right, and the Pueblo tailwater will reward you with some of the finest small-fly work Colorado tailwater fishing has to offer.