In this report
80 CFS: Fish Are Locked in Tight, and You’ll Pay for Every Mistake
The gauge is reading 80 CFS, and that’s a significant problem for Deckers right now. We’re sitting almost half where this water wants to be — well below the 150 CFS floor of the ideal range — and that means the South Platte here is running clear, shallow, and unforgiving. The riffles that usually provide cover and current relief are now thin lanes of pocket water. The deeper runs that hold fish through the day have lost volume and depth. And the fish? They’re concentrated in whatever slow water remains, which makes them hypersensitive to your footfall, your shadow, and your drag.
This is not the week to walk heavy or to fish upstream in a straight line. Every step telegraphs through water this thin. The tradeoff is honest: low, clear water is technical and demands precision, but it also means you can see exactly where trout are holding — if you’re willing to slow down and look.
Blue-Winged Olives Are Your Primary — But Timing Matters in September
September brings the return of fall Baetis activity, and on Deckers that typically shows up in earnest on overcast afternoons, usually between 1 and 4 p.m., sometimes stretching toward dusk if clouds hold. The duns are small — #20 to #22 — and they’re one of the few dry-fly opportunities this week that won’t feel like a complete lottery. Tricos are fading now, which simplifies things considerably.
The real work, however, is subsurface. At 80 CFS and with water temperature almost certainly in the low 50s, midges remain the backbone hatch here — Black Beauty nymphs, Mercury Midges, zebra patterns, and RS2 emergers, all tied #20 to #24. Midges don’t care that the water is thin. They’re year-round on tailwaters (yes, Deckers is a freestone on this reach, but it’s fed by cold outflow from Cheesman Canyon miles upstream, and that cold, stable temperature keeps midge populations consistent). On low water like this, a midge-focused nymph rig will outproduce a dry-fly search by a factor of three or four.
Terrestrials — ants and small grasshoppers — still pull fish in pocket water, especially on warmer afternoon hours, but again, the presentation has to be clean and drag-free, which is harder to achieve on thin, fast current with a size #16 pattern than it is to achieve with a tiny #22 nymph on a dead drift.
Rig Tight and Fish Tight
Here’s the actual setup for this flow:
Use a two-fly nymph rig with a heavier pattern as your anchor and a smaller emerger as your dropper. Lead with a #20 Barr’s Ugly Bug or a chunky #18 Black Beauty — something with enough tungsten to stay down in the 2 to 3 feet of depth you’ll find in the slower seams. Tie a #22 RS2 emerger or Mercury Midge 14 to 18 inches above it on a 4-inch piece of 5X tippet.
At 80 CFS, you don’t need split shot if you’re using a weighted anchor, but you will need to fish tight line or with a small indicator — I prefer an inch-long yarn indicator here, positioned 5 to 6 feet above your anchor fly. The reason: low water is thin water, and any slack in the line means you’ll miss the refusal you didn’t see. Tight line or shallow-set indicator keeps you in contact, and contact wins on finicky water.
Tippet: go 5X on the main strand, 5X on the dropper. At 80 CFS, fish are not running big, and they’re not thrashing in heavy current. 5X gives you sensitivity and a natural presentation without being so light that you’ll break on a snag or a trout that actually commits.
Where to Focus — and Where to Walk Past
The thin riffles at Deckers are almost worthless at this flow. They’re loud and splashy, and they hold very little water depth. Walk past them unless you see actual feeding fish.
Target the slower inside bends where the current slows to a crawl — the kinds of seams that are usually too soft to fish in normal flows but that become oases at 80 CFS. These pockets hold the majority of the trout right now because they’re the only places where a fish can rest without burning calories fighting current.
The deeper slots between fast water — the places where a current tongue breaks and water recirculates — are also worth methodical work. These spots rarely hold huge numbers, but they often hold better fish because they’re less obvious and get less pressure.
Avoid the wide, shallow glides unless you spot actual risers. In thin water, shallow glides are as spooky as they are unproductive.
Water Temp and Fish Welfare
Low water in early September creates a temperature risk, especially if we get a warm day. The South Platte running this lean warms faster than it does at 200+ CFS. If you see thermometer reading above 60°F — and especially if you’re fishing in direct sun — shorten your outing and focus on the shadier sections and deeper water. These trout are pre-spawn browns in some cases, and they’re already under stress. Respect that.
Verify current regulations before you go; the 2-trout over-16-inch limit and flies-and-lures-only rule are the baseline, but regs can shift. CO Parks and Wildlife’s website is your source.
The Week Ahead
This is not a week to bring friends or expect a productive day based on hours of effort. It’s a week to practice presentation, to fish slower than feels necessary, and to remind yourself why precision matters. The water will improve, but right now, patience and accuracy are your only real edges.