Seasonal Colorado Fly Fishing Information for Cheesman Canyon After the Hayman Fire

Despite the adversity of whirling disease, the Hayman Fire, and the water demands of three quarters of a million people living downstream, the South Platte River remains a world-class trout fishery abundant with some of the most finicky and challenging trout in the world. The picturesque, boulder-filled Cheesman Canyon section of the South Platte River is one of the prime stretches. From the base of the 221-foot Cheesman Dam, the river carves its way through a rose-colored granite canyon lined with ponderosa pine, blue spruce, and willow. Boulders as big as Volkswagen Beetles create structure for the river’s super-selective rainbows and browns. Mule deer, black bear, raccoons, mountain lions, rare butterflies, sagebrush lizards, and bald eagles all add to the experience

Hayman Fire

The Hayman Fire was the largest fire in Colorado history, burning more than 137,000 acres in four counties. The area surrounding Cheesman Reservoir was completely devastated and sediment flowing into Cheesman Canyon is a major concern. After the fire, the stream bottom became a graveyard of ash, soot, and silt. The water was gray and as thick as hydraulic oil, and the denuded landscape was left vulnerable to erosion and flash floods

High flows in the fall of 2003 helped free the center channel from the silt, soot, and ash, and the river began to clear. As the autumn season after the fire unfolded, I was astonished to see that the insect life below Cheesman Dam was thriving. Trout eagerly rose to significant numbers of midges, Tricos, and Blue-winged Olives, and anglers reported exceptional dry-fly fishing

The Colorado Division of Wildlife did its annual electro shocking in the fall of 2003, and, to everyone’s surprise, the fish count revealed that there were more fish in Cheesman Canyon than the previous year. The trout somehow survived the off-colored water, and to date they’ve shown no signs of stress. The thick-bodied rainbows are healthy and strong, and if you didn’t know any better, you would never suspect that they lived in almost unbearable conditions throughout the summer of 2003. These fish continue to fight against all odds, and their instinct to survive has amazed everyone

I expect that torrential downpours will be a problem for the next several seasons. Ash, soot, and silt—two feet deep in places—still clog the edges of the stream and flow fluctuations will continue to change the clarity of the stream for several years. Between May and August, heavy rains may wash debris into the river, changing the fishing conditions. Each time it rains, less and less debris is washed into the river. The South Platte will eventually rebound, but it will take time and positive conditions

Whirling Disease & SnailThe South Platte River was a self-sustaining rainbow trout fishery until the appearance of whirling disease. In the glory days, Cheesman Canyon boasted 5,500 fish per mile, with the bulk of the trout being impressive-size rainbows

Brown trout now fill the void where rainbows once thrived. According to a fall 2004 electroshocking survey, there are 3,700 to 3,900 trout per mile in Cheesman Canyon with a 70/30 ratio of brown trout to rainbow trout in the lower canyon and 50/50 ratio in the upper canyon

In April of 2005, New Zealand mud snails were discovered in the South Platte River upstream of Cheesman Reservoir. Only time will tell how this invasive species will affect the fishery

A Day’s Fishing

I typically begin a day’s fishing from the lower end of Gill Trail. You should stock a backpack with supplies for your trip into the canyon. Items you should consider are water, lunch, first-aid kit, sunscreen, rain jacket, and your normal fly-fishing apparel. I recommend wearing waders because the water is very cold

I hike in with all my fishing gear in my backpack and suit up at the river. Since the walk is rigorous, hiking in your waders and vest is uncomfortable, especially if you plan to fish the upper canyon

An ideal flow regime for Cheesman Canyon is between 250 and 400 cubic feet per second (cfs). Winter releases (November-February) average between 50 and 75 cfs. Anything over 700 cfs is high, and the fast, roily currents make for difficult fishing

After I make my way into the canyon, I choose my fishing location mainly based on the current releases from Cheesman Dam. There are constricted areas (such as Lower Narrows, Hell’s Half Acre, Upper Narrows) that fish best during lower flows. The wider sections of the stream (such as Meat Hole, Steel Riffles, Rocky Road, Cleo’s Camp, Indicator Pool) fish best when flows are higher than 250 cfs. Don’t get trapped into fishing the same hole over and over again based on prior success. This rationale limits your growth as an angler

Summer (June-August)

May and June are typically the start of runoff and higher than normal flows, which can range between 600 and 1,200 cfs. In some cases Cheesman Reservoir “spills” (part of the water comes over the spillway), and water temperatures rise because of the warm surface water flowing over the spillway. If this occurs, the fish move into fast, oxygenated water until the water is once again drawn from the bottom of the reservoir. This is the best time to fish aquatic worms and scuds because they get dislodged as a direct result of the increased water volume

There is a three- to four-week period during runoff that I call the “stupid period” because the fish eat anything that resembles a worm if dead-drifted correctly. In time, the trout get wise to these worm imitations, and worms tend to work best early in the season during the high flows. I switch to a small version of a San Juan Worm (tied on a #18 scud hook with micro chenille) when the trout become suspicious of larger versions

Beginning in mid-May, you’ll see sporadic caddis hatches. The best time to experience this surface action is during the late afternoon to the evening, when the fish are “looking up” in shallow riffles and pockets for caddis. A #16 Elk-hair Caddis can be effective in the last two hours of daylight

Throughout June, pale olive midge larvae become important between 8 and 11 A.M. Cheesman trout are stuffed with these larvae this time of year. To imitate these midges, use 8/0 Light Cahill thread on a #18 scud hook and gold wire for a rib

Mid-June through July, Pale Morning Duns (PMDs) begin to hatch. Flows can make or break the dry-fly fishing but nymphing always produces fish. This is the time to switch to a #18 Pheasant-tail Nymph or a #18 PMD Barr Emerger. You don’t always have to fish a #22 or smaller to catch Cheesman trout

In flows less than 300 cfs, plan on excellent dry-fly fishing with adult PMDs. The hatch starts shortly after 11:30 A.M. and lasts until around 1:30 P.M. During higher flows (300-500 cfs) the hatch starts later in the day. After the PMDs, there is often an excellent midge hatch, and the fish continue to feed on the surface for another hour or two

Flies of choice are the #18 Cannon’s Bunny Dun (PMD), #18 Stalcup’s Biot CDC PMD, and a #18 Parachute PMD. Look for the subtle rises of fish in the slow tailouts and deep pool.

The Trico spinner fall begins during the first part of August and is the best dry-fly activity of the season. The duns hatch by 8 A.M., and the spinner fall takes place around 10:30. This spinner fall offers the ultimate dry-fly challenge; it’s like hitting from the blue tee markers in the game of golf. Long leaders (12- to 15-foot) and accurate presentations are required to catch these super-selective surface feeders.

Drowned Tricos are effective after the hatch. Stalcup’s CDC Trico is the best choice when trying to imitate these submerged aquatic insects.

Autumn (September-October)

Autumn brings some of the most consistent dry-fly fishing. By the first week of October, the evenings get cool, so male Tricos don’t hatch the night before and the duns become important. Many anglers confuse Trico duns for Blue-winged Olives, but for practical purposes any #22-24 adult mayfly imitation catches fish.

The best Trico fishing is in the lower canyon between mid-August and the end of September. The best midge hatches of the year start around 8:30 A.M. and last until around 10:30 A.M., then I switch to a Trico dun and fish drys during the Trico hatch. My favorite Trico pattern for the canyon is a #24 Stalcup’s CDC Trico Compara-dun.

Toward the end of September the fall Blue-winged Olive (Pseudocloeon) begins to follow the Trico hatch shortly after 1 P.M. Use small mayfly nymphs (#22-24 RS IIs or Pheasant Tails) or a #24 Parachute Adams if you see trout feeding on duns.

Winter (November-February)

Anglers fish Cheesman Canyon all year but access in the winter is sometimes difficult due to ice and snow covering the treacherous terrain. The canyon receives little sunshine, so dress accordingly.

Until the third week of November you can expect excellent midge hatches in the mornings followed by a tremendous Blue-winged Olive hatch every afternoon between 1 and 3 P.M., and another productive midge hatch around 4 P.M. Fall Blue-winged Olives (#24) are the last mayfly hatch of the year. Depending on the year, it’s not uncommon to see Tricos hatching until the second week of November as well.

The lower canyon has superb dry-fly fishing. The Emerald Pool, the Meat Hole, and the Ice Box always have lots of rising fish this time of year. A #26 Parachute Adams or a #24 Griffith’s Gnat will fool “risers” with regularity at this time of year. Brown trout continue to spawn (which typically starts the third week of October), and egg patterns fished in 18-24 inches of riffled water are deadly.

As Thanksgiving approaches, the trout slip into their slow and deep wintering holes. Dry-fly enthusiasts find a few rising fish in the Ice Box 365 days a year. This is challenging fishing because the fish have a long time to inspect your artificial offering in this deep slow pool. The head of the Ice Box is more forgiving because there are a few distinct seams and more riffled water.

Only an angler who is a master of minutia is effective in the winter months; in fact, December and January offer the toughest fishing of the year. Mercury Blood Midges (#22) are effective, as are #22 Mercury Midges, #22 Mercury Black Beauties, #22 South Platte Brassies, and a #24 Poly Wing RS II Emerger.

Spring (March-May)

By March the big spring midge becomes a major factor. The midge is big by South Platte standards—as a matter of fact, anything over a #18 is gigantic in Cheesman Canyon. It’s common to see two sizes of midges hatching at once. The second midge is the standard small midge, usually about a #24, so I typically fish a #18 Bead-head Black Beauty with a #24 standard gray RS II or a #22 Mercury Black Beauty.

Dry-fly fishing is productive in slow, slack areas such as the Ice Box or the Emerald Pool. A Cannon’s Suspender Midge (#24) or a small Parachute Adams (#26) are great choices.

By the third week of March the rainbows begin to spawn, and this annual ritual can last into June in the lower canyon. One of the biggest areas of spawning activity is in the Steel Riffles, so take extra care not to step on the redds in this section. As you might imagine, egg patterns become effective in the shallow riffles and quick, deep runs.

April is Blue-winged Olive time and the awakening of Cheesman Canyon trout. Flows begin to rise gradually, and fish move into the riffles and start to look for Baetis nymphs. Mercury Baetis, Mercury Pheasant Tails, and Sparkle-Wing RS IIs (#20-22) become the standard fly selection, but midges continue to be an integral part of the trout’s diet when Blue-winged Olives are not hatching. I favor a #22 Mercury Midge with a #22 Sparkle Wing RS II rig for the canyon.

In the spring, you’ll find rising fish in the Meat Hole, Emerald Pool, Ice Box, Jamboree, Blitz, and Rainbow Pools just after 1:30 P.M. Overcast days provide optimum fishing conditions most conducive to rising trout. Prior to the hatch, nymphing is fabulous with small mayfly nymphs. When the hatch begins, the fish move from the deep slots into prime feeding lanes toward the front of the runs where they feed exclusively on mayflies for about two hours. Seasoned anglers make a fly change: two mayfly nymphs, typically consisting of a #20 Mercury Baetis (or Mercury Pheasant Tail), and a #20 Sparkle Wing RS II. I fish with little weight because the fish are suspended and feeding aggressively. Usually one BB is enough lead but in swifter currents, you may need to add some soft weight over the split-shot. This is some of the best nymphing of the year.

These strategies and flies are by no means the only way to approach this fine trout stream, but they have worked well for me over the years.

(Article reprinted with permission of Fly Fisherman)