Cheesman Canyon Hatch Report — June 6, 2026

We’re running 244 CFS on the South Platte through Cheesman Canyon, and this is legitimate fishing water. You’re looking at flows that have dropped from late spring runoff but remain stable enough to keep the river moving with real current. At this level, the canyon presents the kind of balanced conditions tailwater anglers dream about—enough water volume to push food and oxygen through the system, but low enough that fish aren’t glued to the deepest holding water. The dam outlet will still carry significant push, but the mid-canyon sections are opening up nicely.

This flow regime favors subsurface feeding over surface activity for the next week. Fish are positioned in moderate-depth runs rather than tight to the bank, and they’re eating nymphs with conviction. The water temperature is climbing into the upper 50s by mid-day, which activates aquatic insects and accelerates metabolism. Expect solid nymph fishing from first light through mid-morning, a lull during the brightest mid-day hours, and another window starting in late afternoon.

What’s Hatching

Pale Morning Duns dominate the schedule right now. Look for Ephemerella inermis and Ephemerella flavilinea throughout the canyon. Fish nymphs in sizes 16–18 before emergence; as soon as water temperature climbs above 55°F in the afternoon, tie on dry patterns in the same sizes. A reliable combo: Pale Morning Dun Nymphs (tan or olive bodies, sizes 16–18) fished in the column, followed by a Parachute Adams or PMD pattern on top as a loose cover fly.

Caddisfly larvae remain extremely productive. The Hydropsyche species (tan caddis larvae, sizes 14–16) are active in the drift. Fish these as a heavy nymph in the first position of your rig. They’ll work all day—the hatch timing isn’t as locked-in as mayflies, and fish eat the naturals constantly.

Terrestrial insects are beginning to show up in smaller numbers. Ants and small beetles aren’t dominant yet, but having a size 18 Cinnamon Ant in your box is smart opportunistic fishing, especially if the wind picks up.

Small stoneflies (Acroneuria and Calineuria, sizes 14–16) continue to produce. The nymphs are present in good numbers, and occasional adults are on the water in late afternoon. A small black stonefly nymph fished on a tight line through deeper runs will catch fish all session long.

Best Water This Week

Moderate-depth pocket water and broken runs are your primary target at this flow. These are the cobbled, choppy sections where the river pushes around larger rocks but doesn’t form true pools. Fish position themselves just downstream of obstructions, using the current break to hold position while feeding. A 244 CFS flow gives you excellent access to these pockets without blowing fish off—the current is fast enough to turn over food, but not so violent that fish have retreated to the deepest refuges. Nymph rigs work exceptionally well here because the uneven bottom provides plenty of drift depth variation within a single cast.

The soft inside seams along bank structures are consistently productive. Where the main current meets slower water along the canyon walls or along gravel banks, fish lie in the interface. These aren’t slack-water refuges; they’re current-edge holds. Cast your nymph upstream and slightly toward the bank, letting it drop naturally. Fish will be holding 2–4 feet from the bank edge. The softer water allows longer, more controlled drifts than the heavier runs, and you’ll get good depth coverage without excessive weight.

The outflow zone immediately below the dam remains a solid but crowded option. The initial push of oxygenated water carries suspended food, and fish stack up within the first 300 yards. Expect heavier fly pressure here than elsewhere in the canyon. The current is forceful enough at this volume that you’ll need adequate weight to get your nymphs down quickly. This is a good zone if you want numbers early in the session, but you’ll fish better presentations in the sections downstream once you’re warmed up.

Tactics

Fish a two-fly nymph rig: Caddis Larva (size 16) as your point fly, with a Pale Morning Dun Nymph (size 16–18) suspended 18–24 inches above it on a short dropper. Use a 3x or 4x fluorocarbon tippet; at this flow, visibility is good enough that 4x works fine unless you’re in glass-smooth pools. Add a small split shot 12 inches above the point fly—two BB-sized lead weights is typical for these flows.

Employ a tight-line nymph approach: cast quartering upstream, mend once to eliminate slack, and follow your rig with the rod tip. You’re not dead-drifting passively; you’re detecting the moment the nymph bumps bottom or a fish takes. High-stick through pocket water to maintain contact and adjust on the fly.

Switch to a small dry-dropper setup (size 16 Parachute Adams with an 18-inch tippet dropping to a PMD Nymph) if you see surface activity in the afternoon, even scattered rises. You’ll catch more fish on the nymph, but the dry gives you cover and visual reference.

Practical Notes

The Gill Trail gets muddy in places after cooler mornings. Bring appropriate footwear if there’s been recent precipitation—ankle support matters on the technical approach hike, especially when carrying a full pack. Traction is critical.

Water temperature will be warmest in the last two hours before sunset. If you have limited time, plan accordingly. Morning fishing is solid, but the back half of the afternoon often produces better surface opportunities.