In this report
Flow at 298: Right Where You Want It, But Don’t Waste the Window
The gauge is sitting at 298 CFS—dead center in the band where Cheesman Canyon fishes like it’s supposed to. That’s the spread where fish move freely between the tight pocket water and the deeper slots, where your drifts don’t drag, and where you can actually see what’s holding where without the canyon becoming a technical puzzle that only rewards obsession. This isn’t a marginal day masquerading as good, and it isn’t a day where you’re fighting current or chasing scattered fish. It’s the real thing: stable, fishable, and honest.
At this flow, the canyon’s character shows itself clearly. The giant granite boulders that define Cheesh create defined current seams and eddy pockets—the water doesn’t blast through; it works around the stone. That means the trout aren’t bunched into a few slots out of desperation. They’re distributed across the canyon in a way that rewards both reading and persistence. You’ll find fish in the soft water behind mid-stream rocks, in the shallow glides where the gradient eases, and in the deeper slots where the pocket water gets serious. All of those holds are in play right now.
Temperature-wise, June on a tailwater below Cheesman Dam means cool releases from the reservoir—typically in the low to mid-50s. At 298 CFS, the water isn’t warming fast, so fish are active and feeding through the day. This is a window where you can fish without the kind of afternoon shutdown that hits later in summer. Use it.
PMD Emergence into Caddis: The Week’s Rhythm
June is PMD season, full stop. Ephemerella Pale Morning Duns are the marquee hatch on this water, and they’re already happening. Expect emergence to begin late morning—typically around 10:00 a.m. on a stable, warm day—and build through the early afternoon. Sizes run #16–18, and they come off in waves depending on sun angle and water temperature. On the tailwater, that emergence can be surprisingly consistent because the water temperature holds steady.
The hatch isn’t a blitz. Cheesman Canyon is pocket water—hatches here are localized affairs. You’ll see Pale Morning Duns coming off in slow motion in the quieter slots and behind the big rocks, not in a cloud like you’d see on a freestone. Fish will respond to emergers first (often more eagerly than dries), then shift to dries as the bugs thicken mid-hatch. The key is that the hatch window is visible—you’re not guessing. Watch the water. When you start seeing spinners, the emergence is building.
In the evenings, caddis (#14–16) begin to show, particularly in the slower water and in the tailouts of deeper pools where current eases. This isn’t a heavy emergence, but it’s real enough that evening fishing—if you can stay on the water—becomes worthwhile. Evening light in the canyon is extraordinary and the air cools, so fish become less spooky.
Underneath both hatches, and frankly all day, midges (#20–24) are the constant. Zebra Midges, RS2 emergers, and Black Beauties should be part of every rig. On a tailwater, especially in a canyon where the trout are educated, midge-sized nymphs will out-fish larger patterns on most drifts. The Pale Morning Duns and caddis are the conversation starters; the midges are the reliable workhorse.
The Rig That Works This Week
Build your anchor around a heavier midge pattern or a small, weighted Barr’s-style nymph (Copper John, #18–20). Go with a #20 Zebra Midge or an RS2 emerger in black or gray. Weight this point fly enough to feel bottom in the deeper slots—you’re not necessarily crawling, but you want contact with the substrate in the 3–5-foot runs.
Drop a #18 PMD emerger or nymph 16–18 inches above it. Use a small split shot placed 2–3 inches above the dropper—this positioning lets the dropper ride slightly higher in the water column while keeping the anchor weighted. In pocket water at this flow, that’s where PMD nymphs will hang during the emergence window.
When the surface action starts and you’re seeing dries, keep the anchor on the bottom but switch the dropper to a #18 PMD dun (or a #17 emerger that still rides the film)—a yellow or olive body, standard parachute or CDC. Fish this tandem through the slower water behind rocks and in the tail-outs of deeper runs. The heavy nymph below will still catch opportunistic fish, but the dropper becomes your primary contact point.
Tippet: 4X to the first fly, then a 12–14 inch section of 5X down to the dropper. The 4X is necessary on this water—not because you’re throwing large flies, but because the trout here are wild, heavy, and used to light pressure. A 4X won’t spook them on a 298-CFS day, and it gives you enough margin when a 16-inch fish takes hard in pocket water. 5X on the dropper keeps the drifts natural and gives you a better strike-to-hookup ratio on the emerger when fish are focused on rising bugs.
Where to Focus Your Time
In pocket water like Cheesman Canyon, the character of the water matters more than its location. Look for three specific scenarios this week:
Soft water behind mid-stream boulders: These are the most reliable holds at 298 CFS. The current splits around the rock, and trout sit in the cushion of slower water directly downstream of the stone. Approach from below or from the side, and make short, precise drifts. Your fly should enter the soft water and drift 2–3 feet before it swings out of the eddy. This is where you’ll see the most consistent rises during the PMD hatch.
Shallow-to-moderate runs with a visible rocky substrate: Where you can see gravel and small cobble through the water and the depth runs 2–4 feet, trout are often feeding. These aren’t the deepest holes, but they’re where bugs live and where fish position to intercept drifting nymphs. The current is moderate—not sluggish—so your midge-emerger combo will fish naturally without constant adjustment.
Deep slots between larger boulders: These form naturally where the canyon pinches and the gradient kicks up. At 298 CFS, these slots are manageable to wade into, and they hold the biggest fish. The water is 5–8 feet deep in places. Anchor your heavy nymph here, add a bit more weight if needed, and work the drift methodically. You’re targeting the bottom-holding fish that rely on depth for security. These fish will often take the point fly with absolute conviction.
Access and the Hike In
The Gill Trail (#610) is the only way in — the Forest Service lists #610 as a five-mile trail, but that’s the whole thing running up to the reservoir; the walk from the lot to fishable water is about 1.3 miles, with the canyon proper starting around the 1-mile mark. Early June in Colorado means the trail can still have snow in shaded sections at higher elevations, depending on the snowpack. Check conditions before you commit. The steep sections and loose terrain are manageable in dry conditions but treacherous when wet or icy. Budget 30–45 minutes to reach fishable water, more if the pace is slower.
At 298 CFS, the canyon is wading-friendly. The flows haven’t pushed into the 350+ range where wading becomes technical. Still, the giant boulders mean footing is your constant concern—a good wading staff isn’t optional; it’s a necessity. The rock is smooth and slick even when dry.
This is a catch-and-release-only, artificial-flies-only canyon, the first such designation in Colorado history. The trout are wild and large, which means they’re educated. Every other angler on the water is a signal to the fish. Fish deliberately, keep your shadow off the water, and use light tippet. Respect the privilege of being here.
The Bottom Line
298 CFS is the kind of flow where Cheesman Canyon feels like itself—not simplified, not brutal, just clear and honest. The PMD hatch is live, midge fishing is consistent, and the canyon’s pocket structure is fully accessible. You have a real fishing day ahead. Use it.