North Fork of St. Vrain Creek – 04/01/2019

Time: 11:30AM – 4:00PM

Location: Buttonrock Preserve

North Fork of St. Vrain Creek 04/01/2019 Photo Album

A cold front including a minor accumulation of snow moved into Colorado on Friday evening, and I put a hold on my 2019 fishing plans. On Sunday I reviewed the weather forecast for the week beginning on April 1, and I noticed highs in the fifties and sixties in Denver for most of the week. Jane and I made plans to ski on Tuesday, so I was not interested in taking a long trip on Monday, and I evaluated the nearby Front Range options. The most decisive factor was weather, as a high of 58 degrees in Denver translates to relatively cold temperatures at higher altitudes.

I narrowed the choices down to the North Fork of St. Vrain creek, Boulder Creek and the Cache la Poudre in Ft. Collins. Lyons, CO, Boulder, CO, and Ft. Collins all registered forecast highs in the low to mid fifties. The North Fork of St. Vrain Creek is a tailwater, and for this reason it received the nod. I was a bit concerned about flows of 18 CFS, but I reasoned, that I had fairly decent success on South Boulder Creek at that level. The high temperature in Pinecliffe west of South Boulder Creek was 45 degrees, so I postponed a trip to that favorite destination.

I departed Denver by 9:30 and arrived at the parking lot at the gated entrance to Longmont Dam Road a few minutes before 11:00AM. The temperature in the parking area was 44 degrees with occasional wind, so I wore a fleece and light down along with my hat with ear flaps. I rigged my Orvis Access four weight and began hiking up the access road that follows the North Fork of St. Vrain Creek a few minutes after eleven o’clock.

Some Snow on Hillsides

A brisk hike of twenty minutes delivered me to my desired starting point, and I began my day with a size 12 hippy stomper, beadhead hares ear nymph, and RS2. I probed some attractive pockets and runs, as I progressed upstream, but after fifteen minutes there was no sign of trout in the vicinity of my casting. I decided that my second fly needed to be larger and heavier to obtain more depth, so I exchanged the RS2 for an ultra zug bug. The flows were relatively low, but there was enough volume to create some nice deep runs and seams at the head of the pools.

After thirty minutes of unsuccessful fly fishing I found a nice long rock next to a decent pool, and I perched on the edge, while I munched my lunch. Clearly Monday was not evolving in a manner that matched my expectations.

On Display

After lunch I continued upstream, and I finally began connecting with some small fish. A brown trout crushed the ultra zug bug, and this bit of good fortune was followed by a rainbow trout and brown trout that nipped the hares ear nymph. The early fish emerged from slow moving shelf pools next to faster moving deep runs. The catch rate was slow, and I covered quite a bit of decent water, but I was pleased to finally experience some action.

Rising Fish in This Pool

In the time period between lunch and 1PM I approached a long slow moving pool, and I paused to observe before casting. As I surveyed the smooth water ahead of me, I noticed several subtle dimples, and the initiators of the surface disturbance were readily visible in the clear water upstream. I was hesitant to switch to a single dry, so I tossed my three fly dry/dropper system to the scene of the rises. It was a mistake. The trout darted off, and I concluded that the double nymphs and foam dry were too much disturbance for these skittish creatures. I snipped off the three flies and tied a size 24 CDC blue winged olive to my line.


Several fish showed their presence toward the middle of the pool, so I fluttered a cast in that direction, and I was shocked when a brown trout darted to the surface and plucked the CDC BWO. I congratulated myself on displaying the patience to make the changeover, before I released the aggressive feeder. I dried the CDC fluff and resumed casting to the top third of the pool, but my good fortune did not repeat.

I continued my upstream migration, but the next section of the stream was not conducive to prospecting with a size 24 dry fly, so I reverted to the dry/dropper arrangement. Since a trout responded to my blue winged olive imitation, I replaced the ultra zug bug with a sparkle wing RS2 without a bead, in case emergers were on the menu. The idea was worth trying, but the trout did not respond.

Once again I encountered a nice long pool with visible sippers, so I endured the time-consuming conversion to the same size 24 CDC BWO; however, this time I was not rewarded for my persistence. Again after I covered the length of the pool, I switched back to the three fly setup; however this time I knotted a yellow fat Albert to my line and chose an emerald sparkle caddis pupa for the end fly with the hares ear in the middle. I decided to dwell at one place less, move quickly and fish the faster runs and riffles at the head of the pools.

Emerald Caddis Pupa Did Its Job

The strategy more or less worked as I elevated the fish count from four to twelve before I quit at 4PM. I covered .5 mile of the small creek in my 4.5 hours on the North Fork, and I enjoyed moderate success. The largest trout landed over the course of my time on the creek was eleven inches, and most of the fish that nestled in my net were in the eight to nine inch range. Five of the last eight crushed the emerald caddis pupa, so that proved to be a fortuitous fly choice. Two more favored the hares ear, the last fish of the day slurped a size 14 olive-brown deer hair caddis.

I was near my end point, and I was about to strip in my flies to hook them to the rod guide before climbing the bank to exit. I glanced downstream and spotted a decent rise ten feet below me and four feet from the opposite bank in front of a large submerged boulder. Since I considered removing the three flies that comprised the dry/dropper, I completed that plan and pulled a size 14 olive-brown caddis from my box. This would be a last ditch attempt to dupe the source of the solitary rise across and below my position.

A Rare Rainbow on the North Fork

I stripped out adequate line and tossed a downstream cast. I checked the line high and allowed coils of slack to pile above the fly, and then it slowly drifted downstream. Unfortunately the line of the drift was off by three feet, but it did not matter, as suddenly a trout slowly emerged from the depths, and then it confidently slurped the deer hair caddis. I instinctively reacted with a hook set, and I quickly guided an eleven inch rainbow trout into my net. Needless to say I was quite thrilled and surprised with this late afternoon action. I persisted with the dry/dropper for most of the afternoon, and now I chastised my stubborn resistance to change. Perhaps prospecting with an adult caddis was the ticket to greater trout numbers? I’ll never know the answer to this quandary, but I do know that I generated two additional temporary connections with the caddis, when I deployed long downstream drifts through the tail of the pool.

Adult Caddis in Lip

Upon reaching the tail I stripped in the caddis and hooked it to my rod guide with the intention of testing several additional smooth pools along the road on the return hike. It never happened. I was weary, and it was after 4PM, and accessing the pools required scrambling over some large boulders on a steep bank. I adopted a comfortable pace and returned to the car for the drive back to Denver.

Twelve small trout in 4.5 hours of fishing is a decent record of success. The weather was chilly but tolerable, and the wind was present but never insurmountable. Two of the landed trout sipped dry flies, and that was a plus for early in the season. The hatch, if there was one, was very sparse. In fact I never actually saw an insect larger than a very small midge. Two of the twelve trout were rainbows, and the caddis eater at the end of the day was an eleven inch rainbow.

Fish Landed: 12

3 thoughts on “North Fork of St. Vrain Creek – 04/01/2019

  1. Dave,

    I wanted to thank you for the abundance of knowledge you’ve taken the time to share on this blog. I’ve been reading since my first CO trip last summer, but was particularly appreciative this past week as plans unexpectedly changed while in Denver on business. A planned four days on 11-mile unfortunately had to be cancelled, but I still wanted to squeeze in at least a morning on the water between my conference Friday and return flight Saturday afternoon. I quickly searched your blog and settled upon Button Rock due to proximity to the airport.

    While my day consisted primarily of refusals and one decent rainbow that popped my tippet, your blog allowed me to salvage what might have otherwise been a lost trip. Fish or no, it was a beautiful morning on a stream I hadn’t explored previously and I greatly appreciate this resource you have provided to all of those who read it.

    Thank you for taking the time and effort to share.


    • Chris,
      I’m humbled by your kudos. My blog is my online fishing log, and I do it for my own documentation and also because I love to write. Being able to help others enjoy the wonderful sport of fly fishing is just a bonus. I’m pleased that you salvaged some fishing on your trip. Hopefully you will return to Colorado and make it to Eleven Mile. Dave

      • Thankfully, I’ll have the opportunity to spend two days at Eleven Mile in August as a brief prelude to a week of hiking/fishing the IPWA. I look forward to following your adventures in the interim, however.


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