South Park Stillwaters

In the giant valley of South Park, surrounded by what seems to be an endless sky, the reservoirs of Antero, Spinney Mountain, and Elevenmile provide an angling paradise within easy striking distance of the Front Range. The three reservoirs are within a 20-minute drive of one another, with quality trout feeding in large schools during the spring, summer, and fall.

For fly anglers, the season starts when the ice begins to melt around the edge of the reservoir or opening day when the ice has disappeared completely. Spring is one of the best times of the year to pursue large trout, with openings of warm water supplying food and triggering the fish into pre-spawn mode. This window of edge-fishing opportunities can vary depending on the weather, sometimes only lasting a few weeks during warm springs, and longer if the season remains cold.

After ice-off the water continues to warm, causing vegetation growth and insect activity as the season draws closer to June/July and the sun penetrates the water. These are the most productive months to pursue trout on all three reservoirs. The hatches are complex and huge in number, causing a feeding frenzy.

This activity lasts late into the month of August, until the water starts to cool and the insect activity begins to slow down. While you can still effectively pursue trout, you often need to fish deep. Once the water reaches a cooler temperature in late September, the browns start becoming active in their eagerness to migrate. This can produce some exceptional results from these nocturnal predators in overcast or low-light conditions.

Spinney Mountain Reservoir

What sets Spinney Mountain Reservoir apart from others in the state are the regulations. For the first five years after Spinney’s opening, it was an unbelievable trophy trout reservoir. This was caused by an abundance of high-protein scuds that inhabit every bit of this stillwater. However, with a big bag limit and heavy angling pressure, it did not take long for the state to realize it had to enforce stricter regulations to save a unique stillwater fishery.

This large body of water is approximately 46 feet at its deepest point, making it mostly an ideal depth for fly fishers to reach the trout. You can only use flies and lures, and there is no night fishing or ice fishing. The reservoir is closed from when it freezes over until opening day in April or May. All this in addition to bag limits of one trout over 20 inches makes Spinney a well-kept treasure.

Over the last five years the numbers and size of the trout have increased, and should continue to do so for years to come. The key to this success is managing the pike population to a minimum, allowing the trout to continue to reproduce and grow to their full potential.

There is no road that provides access to the entire reservoir, and there are many locations that boats cannot navigate to effectively, requiring a substantial hike. You can either park in the first parking lots after you enter the state park and start hiking northwest around the shoreline, or you can park at the south end of the reservoir to explore the far side.

If there is a good chop on the water, try hanging a three-fly rig on 3X or 4X fluorocarbon that includes a size 16 or 18 Prince Nymph, a size 16 or 18 Copper John in copper or red, a size 16 scud, size 12 to 16 Mayer’s Mini Leech Jig, or size 12 to 16 Znail, all 12 to 18 inches apart in that order. Depth control is an important consideration, so use a large, clear Thingamabobber and constantly adjust it to test different depths.

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In calmer conditions a damselfly like a size 12 or 14 Blue Damsel, a hopper-size 10 to 14 Fat Albert, or a Callibaetis imitation such as a size 12 to 16 Parachute Adams can produce awesome dry-fly action if it is one of those lazy summer days early in the morning. Or, if you are up for some heart-pounding action, lob a large attractor pattern and watch these fish crush what they think is an easy meal!

This reservoir sits in what used to be some of the most productive ranchland in the area (mostly Sam Hartsel’s ranch, for which the town is named), and it is teeming with hoppers. With such an abundant food source living along its shores, the opportunistic fish in this reservoir can’t resist large meals.

Unlike in a river where the current carries hoppers to waiting trout, in a lake you have to get your hopper in front of cruising fish.

Throw a hopper in a lake sometime and you’ll see that it kicks its legs every once in a while, but doesn’t make much progress. Your hopper should do the same, so twitch it to make it appear alive, and then let it sit for ten seconds. Keep it in the zone along an edge or a drop-off where trout are likely to be feeding. It’s also effective to use the hopper as an indicator, and hang a Callibaetis nymph or a chironomid pattern off the bend of the hook.

ElevenMile Reservoir

Unlike its neighboring stillwaters, Elevenmile Reservoir is a trophy trout factory known to grow fish in large numbers, some of them up to 20 pounds. With water depths reaching 100-plus feet, some of these fish feel no angling pressure for a majority of their lives. Elevenmile Reservoir supplies the Front Range with an astonishing amount of water storage, and trout migrate upstream from the reservoir annually in the spring and in the fall. This is how the section of South Platte River between Elevenmile and Spinney Mountain Reservoirs got the nickname “Dream Stream.”

Because it’s so deep, this reservoir is best at ice-off or in the fall. Every year ice-off comes at a different time, and you can monitor it by keeping track of when the ice fishing stops by checking the report at the 11 Mile Marina (11milesports.com). Some years it can be brief, some years it is longer, but if you have cabin fever and are going to battle the crowds on the Dream Stream anyway, you may as well investigate. This is the time when these monsters cruise the warm shallows in search of food without the lurking predator pike.

There are three year-round food supplies for the trout in Elevenmile: crayfish, freshwater scuds, and four-season chironomid midges. These three abundant food sources keep the trout healthy in even the toughest ice and snow conditions, and the months that follow. Following the midges from late spring through the summer and early fall are three additional food supplies: Damselflies, caddis, and Callibaetis mayflies.

Once ice-off is over, the trout disperse, and finding them can be a challenge in this vast, deep water. If you want to hike, park at the Cross Creek fishing access and head on the trail south along the reservoir. There are some awesome drop-offs in this area.

The browns stage in these places, and we have seen rainbows as long as a coffee table cruising the shelf line. Alternatively, on the other side of the reservoir, Rodgers Mountain fishing access can be productive.

Local Insights 

One of the best ways to succeed on any fishing adventure is through preparation, and that all grows out of local knowledge. You learn through observation and through trial and error when you are on the water, but in order to properly prepare you need to have conversations with other anglers, and networking is a great way to learn. 

Tyler Swarr, aquatic biologist for the Upper South Platte Basin, has shared a wealth of knowledge with me, and I credit him with much of the success of these fisheries. The operations at North Delaney Butte Lake and Antero normally provide all of the brown trout eggs for Colorado hatcheries.

“The brown trout spawning operation at Antero has been going on since 2012 and is conducted to take pressure off of the North Delaney Butte brown trout spawning operation by reducing the amount of time it takes for us to meet our brown trout egg request,” says Swarr.

“We did not take eggs from Antero in 2015 through 2017, as the reservoir was drained in 2015 and the fishery was in a rebuilding phase. We had modest success spawning in 2018 and saw an increasing trend in the number of mature trout showing up in the nets compared to 2017.

“Eggs taken from the spawning operations are brought to the hatcheries, and the fish are typically grown to about 3 inches long before being stocked out. A portion of the browns hatched from the North Delaney and Antero spawning operations are stocked back into those lakes to ensure there will be a reproductive cohort in two to three years. The remaining fish are stocked across the state.”

Rob Robinson, owner and operator or the Chaparral Park General Store, literally eats, sleeps, and breathes Spinney Mountain Reservoir. He always has useful advice for stillwater fishermen: “I think of Spinney Mountain Reservoir in two sections, the west (plateau) side of the stillwater with average depths ranging from 2 to 8 feet. This is a great feeding area for large trout that cruise in search of midges, dragonflies, damsels, Callibaetis, and caddis on and below the surface. This is highly oxygenated, fertile water due to the influence of the South Platte River.

“The east and deepest side of the reservoir plummets down to 45 feet at the dam providing great cover, oxygen, and food during all seasons. The depth near the dam allows the trout to avoid predators like pike and prevents the chance of winter kill. The best feature of this side of the lake is the Homestake Pipeline that, at peak flow, can deliver 75 cubic feet per second of fresh, cold, oxygenated water.”

Depth also plays a vital role: “Elevenmile Canyon Reservoir is around 130 feet deep near the dam, but shallows up considerably as you move toward the inlet with the Dream Stream,” says Swarr. “The variety of depth and large boulders provide a diversity of habitat for trout living in the reservoir. The depth also reduces the likelihood of winter kill. Fish the shallows to catch Snake River cutthroats. Cuttbows are throughout the reservoir, but the browns are mostly in deeper water.”

Antero Reservoir

Antero is one of the best fly-fishing stillwaters in the U.S. With depths only reaching 18 feet at its deepest point, conditions are ideal for anglers to get their flies to the trout from almost anywhere on the water. While Antero has constantly produced a wealth of quality fish, it has been opened and closed twice since 2002, once to rid the reservoir of invasive species, and another time to repair the earthen dam.

The most recent opening in 2017 supplied great specimens up to 10 pounds. To help control the sucker population, Colorado Parks and Wildlife also added tiger muskies to the mix of species. With an early opener, CPW did its part by not allowing boats on the reservoir in order to provide less stress for potential growth. These trout can grow at a pace of 1 inch per month.

Regulations previously allowed a four-trout limit, with only one exceeding 20 inches, but now the limit is two trout, allowing the smaller trout a chance to grow to their full potential. Hopefully in the near future the regulations will only allow flies and lures, giving these giants a fighting chance every time they are returned to the water.

Antero sits over an existing spring-fed stock pond that was used in the early days on the homestead. This “reservoir within a reservoir” creates a depression where large trout feel safer. The rest of the water is quite shallow until right before the dam.

South Park Tactics

A typical summer day on the reservoirs begins with chironomids and scuds in the early morning hours followed by damsels, Callibaetis, and dragonflies into mid- or late afternoon. Protein-rich meals of baitfish, crayfish, and eggs are often on the menu.

As with any river or large body of water, determining the best imitation can sometimes seem overwhelming. With the number of good flies to choose from for stillwaters, I prefer to carry productive imitations of the four main food groups to narrow down my selection. The four main food sources in these stillwaters are scuds, chironomids, mayflies, and damselflies. The advantage to this is you will build confidence in flies that always produce, taking the mystery out of fly selection. Learning the time when the insects are most active will help you determine which fly of the four is right for the job.

During the spring and fall, the ideal time to be on the water can be early morning or late evening. In addition to cloud-filled, stormy days, this gives the trout cover while hunting the shallows for food and territory. These shallow environments also heat the water temperatures rapidly.

In the spring in the late afternoon hours, the winds tend to pick up in this valley, blowing whitecaps into the bays surrounding these reservoirs and at the dams. These are must-fish situations because the entire surface warmth on the water is blown into the bay, along with a huge food supply stirred up from the bottom of the reservoir. Anglers beware: The same storm that stirs up the food can get ugly really quickly!

The first and most common way to present your flies in many stillwaters is to suspend them below an indicator capable of suspending heavy rigs, with a 9- to 12-foot 2X or 3X fluorocarbon leader attached to two pieces of 18- to 24-inch tippet material matching the leader strength connecting the two flies. This allows you the chance to adjust to different depths throughout the day by merely moving your indicator.

One trick I use is weighted flies with split-shot on the bottom—essentially a drop-shot rig for stillwaters. This gives a slow rise and fall to your flies, keeping them more visible to cruising trout. I slowly strip in a few feet of line periodically in between pauses. This resembles the movement made by emerging insects.

A second effective way to present your flies is with a 15-foot 2X or 3X fluorocarbon leader. For deepwater situations, use a shorter leader of 6 to 7 feet attached to a sink-tip or full-sink line to get the flies deep and remain there during the retrieve.

Using a hand-over-hand retrieve allows damsel, Callibaetis, and crayfish patterns to look natural to the trout, giving them a chance to attack a slower-moving fly. If the fish are aggressive, the advantage to these rigs is the ability to change to a fast retrieve with multiple pauses. This will allow you more ways to manipulate your imitations to look like the meal the fish are pursuing while adjusting to the water depth.

The pursuit of rising trout in stillwater is not only a challenge, but also an incredibly rewarding visual experience. The key is to use a long monofilament leader with an 18- to 24-inch fluorocarbon tippet to keep the trout from detecting the fly line.

Unlike their river-dwelling counterparts, trout rising in stillwaters are always on the move, and you cannot present in the same place with every cast. Instead, the key is to see the direction of the trout’s head to know where it is searching. Once you determine this, lead the fish by 2 to 3 feet, giving it a chance to locate its next meal. This will result in more sips followed by a rewarding acrobatic leap into midair.

The wonderful thing about our sport is the vast areas we pursue, the prized catch, and the challenge that goes along with the hunt. This is what makes these three stillwater gems worth pursuing. These are some of the strongest trout in this vast valley, and it all begins with the promise in spring of another wonderful year of rod-bending madness.

* Landon Mayer is a Colorado fly fishing guide and Fly Fisherman contributing editor. He lives with his wife Michelle and their four children in Florissant, Colorado. Portions of this story were excerpted from the book “The Hunt for Giant Trout: 25 Best Places in the United States to Catch a Trophy” (Stackpole Books, 2018).