In this report
72 CFS: Ultra-Technical Water, Fish Under Pressure
The gauge is reading 72 CFS — well below even the low end of what makes Cheesman Canyon genuinely approachable for most anglers. This is not a crisis, and it’s not unusual for early October. But it is a condition that demands respect and a hard honest look at what you’re actually walking into.
At this flow, you’re operating in experienced-angler-only territory. The pocket water that defines the canyon — those glass-clear slots between granite boulders — shrinks. Holding water compresses. Fish that would spread across a wider range of depth and current at 265–305 CFS are now concentrated in the deepest runs and behind specific rocks. Every fish you approach has been looking at fake flies for months. The water is transparent enough to read a newspaper through. Wading becomes a study in slow, deliberate placement and long leaders.
The upside: the trout are there, and they’re large. The downside is that they’re also educated and spooky. If you’re comfortable on small, technical water — if you’ve built your skills on 5X tippet and tiny nymphs — this is your kind of week. If you haven’t, the hike in to the canyon entrance is still beautiful, but the fishing will be humbling.
Midges and Fall BWOs — Size Matters More Than Species
October on a tailwater below Cheesman Dam means midges first, always. They’re the year-round protein here, and at 72 CFS, when fish are concentrated and selective, they’re the foundation of what will work.
Fish a #20–24 midge dropper. Black Beauty, Mercury Midge, and Zebra Midge patterns all move fish — the color and exact pattern matter less than presentation and size. The #20 Zebra Midge is probably your safest call: it’s visible enough to track, realistic in profile, and proven. Pair it with a #20 or #22 RS2 emerger as your second dropper — the emerger shape and the way it sits in the film triggers takes even when the pupa gets refuses.
Gray-sky conditions might bring fall BWO activity, and you should carry #20–22 BWO dries. But “might” is the operative word. The midge is the reliable hatch. The BWO is the bonus.
On this flow, color shifts toward the subtle: dark olives, blacks, and grays. Avoid anything bright. A #20 black midge on point, an RS2 emerger 14 inches below on 5X, and a tiny gold-bead dropper another 10 inches down will be your bread-and-butter rig. The gold bead is there for visibility — yours, not the fish’s — and to anchor the rig without adding split shot if you can get away with it.
Rigging for 72 CFS: Weight, Tippet, and the Tight-Line Game
At this flow, you need to get down without spooking fish. That means careful weight placement and zero wasted motion.
Use a single split shot — a size BB at most — positioned 18 inches above your point fly. This keeps weight off the furthest downstream tippet section and lets you make shorter, more controlled casts. A longer leader helps enormously: 12 feet of 4X main tippet, then a 2-foot section of 5X to your point fly, then 5X droppers. The extra length gives you the reach to place the rig in the sweet pocket without your line or body being visible to the fish.
Tight-line nymphing is better than an indicator at this flow. An indicator at 72 CFS is like announcing yourself. Mend tight, keep tension on the line, and feel the tick. You’re fishing 18 inches to maybe 2.5 feet of depth in the main channels — the pockets won’t be deeper, and the fish won’t move far to take. Dead-drifts of 3–4 feet are plenty. When the line twitches, set immediately. Fish are taking out of reflex, not confidence.
If you must use an indicator, use a small, dark one — a tiny pinch of putty or a small yarn wrap, not a strike thingamajig. But honestly, tight-line is cleaner here.
Where to Spend Your Time
At 72 CFS, the working water is specific. Skip long stretches of marginal glide. Target the deep slots between and behind the giant boulders that define the canyon — the pockets where current funnels and depth is genuine. These are the only places holding fish at this flow. The shallow flats and marginal seams are wasted effort.
The tight, bouldery sections hold better than the wider, slower runs. Work the granite-pocket water carefully. Make short, controlled drifts. Wade deliberately and position yourself downstream and across from the fish, not directly behind. This is where the canyon’s teaching reputation comes from: the water won’t forgive sloppy footwork or lazy casting.
One Stewardship Note
At 72 CFS and early October, water temperature is dropping but still worth monitoring. If the canyon is running above 55°F, fish are less stressed and will recover quickly from a tough landing. If it’s closer to 50°F or lower, play fish to hand quickly and handle them minimally. The hike is long, the fishing is demanding, and these are wild trout — land them efficiently and release them fast.
Bring water and a thermometer. The canyon walls keep it cool, but a thermometer takes the guesswork out of whether you should extend your session or call it early.