Nobody is going to give you a blue line. If a creek is good enough to write about by name, it’s good enough that naming it ruins it. So this isn’t a list of secret spots — it’s how I find my own. The finding is most of the fun anyway.
I do almost all of it from my couch in Colorado Springs with a map open, long before I ever load the truck.
The short answer
To find your own blue lines in Colorado, open a topo map and pick the small perennial creeks (solid blue lines) branching off rivers you already know, then filter them for gradient, cold high elevation, connection to a known fishery, and legal public access — USGS topo maps for the terrain, the CPW Fishing Atlas for regulations, and onX or CalTopo to sort public from private. Do that homework from the couch first, build a short list of three or four, then go look — half will be duds, and the one in ten that’s a gem is the whole point.
Read the Map
The name “blue line” is literal. On a topographic map, every flowing creek is a blue line, and the small unnamed ones branching off the rivers you know are where you start looking.
A few tools do the work:
- USGS topo maps — the classic. Shows gradient (how tight the contour lines are), elevation, and whether a creek runs year-round (solid blue line) or dries up (dashed).
- Colorado Parks & Wildlife Fishing Atlas — free, and it overlays public access, species, and any special regulations onto the map. Start here for legality.
- onX or CalTopo — for sorting public land from private. This matters more than anything else on the list. A great creek you can’t legally reach is worthless.
The whole first pass happens at home. I’ll spend a winter evening with onX open, dropping pins on creeks that look promising, cross-checking gradient against access, building a short list of three or four to go look at once the snow’s off. By the time I actually drive out, I’ve already eliminated the obvious duds — I’m not exploring blind, I’m confirming a hunch. That homework is the reason a scouting trip ends in fish more often than it ends in a shrug.
What Makes a Creek Worth the Hike
Not every blue line holds fish, and not every fishable one is worth the walk. Here’s what I look for before I commit a day to it:
| What | Why it matters |
|---|---|
| Gradient | Some drop, not a waterfall. Tight contour lines = pocket water and plunge pools. Too steep and it’s all whitewater; too flat and it’s a marsh. |
| Perennial flow | A solid blue line that runs all year. Dashed lines dry up by August. |
| Elevation | High enough to stay cold through summer. Cold water holds trout when the lowland creeks get too warm. |
| Connection | A creek that feeds or drains a known fishery often shares its fish. Trout move. |
| Access | Public land, a legal way in, and a hike most people won’t bother with. The walk is your crowd control. |
When a creek checks most of those boxes, it goes on the list. Then I go look.
My take
Half the blue lines I scout turn out to be duds — too small, too warm, too hard to reach, or just plain empty. That’s not failure, it’s the cost of admission. The one in ten that’s a gem is worth the nine that weren’t, and nobody can hand you the shortcut. That’s the entire point of the exercise.
Gear for Small Water
Blue lines are where short, light rods make sense. My Scott F Series 3-weight lives for this — a 7’2” glass rod loads at close range and fits between the streamside brush that eats longer rods alive. A click-pawl reel, a floating line, and one box of flies. That’s it.
Keep the rest minimal:
- A small net you can clip and forget
- 9-foot 4X–5X leaders (you rarely need finer up here)
- Polarized glasses — you’ll be sight-reading shallow pockets
- Good boots and a willingness to bushwhack
The whole point is to move light and cover ground. If you’re carrying a tailwater rig up a mountain, you brought the wrong kit.
Tactics
Small-creek fishing rewards the opposite of everything tailwater fishing teaches you.
Move upstream, and move slow. Fish face into the current, so approaching from downstream keeps you behind them. On water this small and this clear, the fish will see you long before you see them. Crouch. Use the brush. Keep your shadow off the water.
Cast short. Most of my casts on a blue line are under 15 feet. A lot of the best ones are a bow-and-arrow flick or a dap straight down into a pocket. Distance is not the skill here — accuracy and a soft landing are.
Fish the structure. Every plunge pool, every seam behind a boulder, every undercut bank and bubble line holds fish. Hit the head of the pool first, then work it back. Then move on. You don’t need to grind a spot — if a fish is home and didn’t see you coming, it usually eats.
Run a dry-dropper. A buoyant attractor dry with a small nymph hung 12–18 inches below covers both the surface and the column at once. It’s my default rig on a creek. (More on how I rig it in the dry-dropper guide.)
Flies
Don’t overthink this. Wild creek trout are opportunists, not critics. A handful of patterns covers almost everything:
- Attractor dries — a Royal Wulff, a Stimulator, a parachute hopper. Big enough to see, buggy enough to eat.
- An Olsen’s Blowtorch as the dropper. It’s my confidence fly everywhere, and small water is no exception.
- A few small nymphs — a Perdigon or a Pheasant Tail, size 16–18, for the deeper pockets.
If the fish are eating, they’ll tell you fast. If a pool goes quiet, it’s almost always because they saw you — not because you tied on the wrong bug.
Frequently asked questions
What rod should I bring to a blue line? A short, light one — a 6’6”–7’6” 2–4 weight. I fish a 7’2” 3-weight glass rod; it loads at close range and slips between the streamside brush that snaps longer rods. A 9-foot 5-weight is too much stick for tight creek work.
How do I find blue lines if nobody will tell me where they are? That’s the method, not the obstacle. Open a topo map, find the small perennial creeks branching off rivers you already know, filter for gradient, elevation, and public access with onX or CalTopo, then go look. The scouting is most of the reward.
Are blue-line trout easy to catch? Easier to fool, harder to approach. Wild creek fish rarely see flies, so they’ll eat a well-presented attractor without much fuss — but they spook at a shadow or a clumsy step from twenty feet out. The challenge is the stalk, not the fly selection.
Is it legal to fish small unnamed creeks in Colorado? Often, but check first. Public-land creeks are generally open; some are catch-and-release, seasonally closed for spawning natives, or inside cutthroat-recovery areas. The CPW Fishing Atlas and your license spell it out — read before you go.
The Ethics of Blue Lines
This part matters more than the fishing. Small streams are fragile, and the wild and native fish in them — especially Colorado’s cutthroat — can’t absorb pressure the way a stocked tailwater can.
- Don’t name them publicly. Not on the internet, not in a geotag. A blue line stays good because almost nobody knows about it.
- Check the regulations first. Some Colorado streams are catch-and-release, some are seasonally closed to protect spawning natives, some are part of cutthroat recovery areas. The CPW Fishing Atlas and your license cover this — read before you go.
- Handle fish fast, keep them wet, and pinch your barbs. These fish are the whole resource. There’s no hatchery truck restocking a backcountry creek.
- Leave no trace. Pack it out, tread light, and walk the same line in and out.
Find your own, fish it quietly, and keep it to yourself. That’s the deal. Do it right and you’ll have wild trout and an empty drainage for a long time.