In this report
Flow Is Low—Fish Are Concentrated, and So Is Pressure
The gauge is running at 79 CFS. That’s well below the 150–400 CFS band where Deckers fishes its best, and it means you’re dealing with a version of this water that rewards precision and punishes carelessness. The upside: fish have nowhere to hide, so they’re stacked in the deeper slots and current tongues. The downside is they’re also spooked easily, water temperature stays elevated longer into the afternoon, and the thin, clear current makes every sloppy cast visible.
This is honest-water fishing. Your approach matters as much as your flies.
Baetis and Midges—Fall’s Quiet Dual Hatch
September on the South Platte brings a return of Blue-Winged Olives—Baetis in the #20–22 size—and they’ll show up on overcast afternoons when cloud cover drops the light and water temperature slightly. Don’t expect a violent spinner fall or a dense cloud of duns; this is a measured autumn emergence, and the fish respond selectively rather than aggressively. It’s worth noting because it gives you a dry-fly window when the sun ducks behind weather, but it’s not the reason you’ll catch fish this week.
Midges are. They always are on this water, and they’re your bread-and-butter right now: black beauties, mercury midges, zebra midges, and RS2 emergers in #20–24. At 79 CFS, midges fished deep in the film and just subsurface are going to account for most of your grabs. They’re present all day, predictable, and—in low water—concentrated where the fish are holding.
Terrestrials still work: ants and small hoppers in #16–18 on the banks and in the shallow, slower edges where they drift naturally. But at this flow, don’t waste time on the very thin water along the margins. The real fish are in the medium-depth slots and the current tongues where the flow has enough velocity to hold them but isn’t so fast it demands constant energy.
How to Rig and Fish This Week
Dropper rig, tight-line or indicator—your choice depends on where the fish are sitting.
Use a heavier nymph as your anchor—a Barr’s Styrofoam body pattern or a tungsten #18 midge pupa works—and hang an 18-to-24-inch dropper of lighter stuff above it. That lighter fly should be your #20–22 Baetis nymph during overcast spells, or a #22 RS2 emerger or zebra midge when the light is hard. Tippet: 5X on the main line, 6X on the dropper. At 79 CFS, the fish are close and the water clarity is high; thinner tippet matters, especially if you’re fishing tight-line.
For tight-line: Use split shot pinched to the main tippet, roughly 12–18 inches above the point fly, to get the rig to the bottom quickly and keep it tracking the riverbed in the deep slots. Don’t overthink it; one or two split shot is usually enough in this low flow. Dead-drift is the standard—follow the rig with your rod tip, feel for the weight ticking the bottom, and set hard on any pause or slight resistance.
For indicator: A small yarn indicator or a tight-line setup with a strike indicator clipped 4–5 feet above your dropper gives you more visibility and lets you fish slightly slower water without worrying about detecting the take. The trade-off is that an indicator spooks fish in this clear, thin water if you’re not careful with your cast. If you go indicator, place it well upstream of your target water and let the rig settle before it drifts into the zone.
The water types worth your time:
—Riffle edges: where the faster, choppy water meets a slightly deeper slot on either bank. Fish hold just off the main current tongue, feeding on nymphs and emergers tumbling through.
—Deep runs: the 2-to-4-foot slots in the middle and along the far side of the channel. These are your bread-and-butter at 79 CFS. Fish them deep and slow, with emphasis on dead-drifting the emerger or midge pupa through the center of the slot.
—Behind and beside mid-channel rocks: small current shadows where fish rest out of the main push. Don’t ignore them just because the flow is low; they’re still holding fish, especially in the afternoons.
Avoid the thin, glassy water in the margins. It’s clear and cold-looking, but at 79 CFS it’s too exposed and too warm by midday.
A Stewardship Reality
At this flow and with September light still strong through the day, water temperatures are probably climbing into the mid-60s Fahrenheit by early afternoon. Deckers allows two trout over 16 inches, flies and lures only, which is more liberal than the catch-and-release-only rules upstream in the canyon. But if you’re keeping fish in these conditions, keep them early (morning and early afternoon) when the water is coolest, or release them if the water has warmed. Fish stress quickly in low, warm water, and a careless kept-fish in September on a 79-CFS day is a dead fish.
Verify current regs before you go—they can shift year to year.
Bottom Line
Low water, clear conditions, concentrated fish, and a manageable but not explosive hatch window. This is a week that rewards discipline: small, specific flies, accurate casts, gentle presentations, and patience in the right current seams. The Baetis hatch will give you an occasional dry-fly window on overcast days, but your real fishing happens below the surface with midges and emergers worked methodically through the deep slots. Park at one of the accessible sections along CO-67, fish the riffles and runs nearest the road, and focus on the medium-depth water. September is crowded here on weekends, and low flows make every angler visible—go early or midweek if you can.