DIY Guide to Fly Fishing the Big Thompson River in Colorado

Known locally as “The Big T”, Big Thompson River makes it headwaters among the heights of the Rocky Mountain National Park in Forrest Canyon before making its way down the mountainside through Estes Park, then feeding into Lake Estes before winding along highway 34 all the way to Loveland, CO.

If you are keen to fish the headwaters, it is best to only make the journey in good weather midsummer, and then if and only if you are an experienced backpacker or hiker.

The trails near Forrest Canyon are treacherous even under the best of conditions, and they can be downright lethal in bad weather. Downstream of Forrest canyon though, there is some truly excellent fishing to be had, especially for those in search of rainbows, cutthroats, and browns.

Big Thompson River below Forrest Canyon is best known for its free stone stream fishing, so pocket water and riffles abound up and down the length of the river along Highway 34. Keep an eye out for the private property markers along the river banks though, as there are sections of the Big T that are strictly off limits to pedestrians and anglers alike.

The trout in Big Thompson River are largely born in the wild and range in size from 10-12 inches. The river has not been stocked since the mid 1990's.

If you aren’t intimidated by steeper, faster water and love to fish pocket water and riffles, the Big Thompson River is definitely a fly fishing destination for you.

Big Thompson River Map and Fishing Access Sites

map of fishing access spots on the Big Thompson River in Rocky Mountain National Park

Get directions to fishing access points and real-time stream flow data with the DIY Fly Fishing Map

Best Places to Fish the Big Thompson River

The safest access point to the Upper Big T is definitely Moraine Park, and fishing is best upstream along the trails and streams that feed into the Big Thompson River throughout the park. It can get a little marshy during runoff and after heavy rains, so plan accordingly if you are looking to hike in search of your ideal fishing spot. If you do decide to fish among the meadow lands in Moraine Park, keep in mind that you need to approach quietly so as not to spook the fish, as there is little cover and brush nearby.

The best fishing on the river is below Lake Estes is along Highway 34, as there is more public access and the river is consistently free stone stream fishing for the majority of its run all the through Idlewild Dam to Viestenz-Smith Park.

The river does tend to take a steeper grade the further downstream you go, but overall the pockets and riffles here yield some very large trout for those willing to brave the more difficult terrain.

Be mindful of the private property that dots the length of the Big T along the tailwater section, and a good rule to follow is that the riverbank on the highway side is usually public, but the banks opposite Highway 34 are not.

Big Thompson River Flow and Current Conditions

BIG THOMPSON BL MORAINE PARK NR ESTES PARK, CO

  • Temperature: 35.78 ° F
  • Streamflow: 106 ft³/s
  • Gage height: 5.00 ft
Temperature GraphStreamflow GraphGage height Graph
USGS

Best Time to Fish the Big Thompson River

Provided you steer clear of Forrest Canyon in the winter, fishing is solid all year round along the length of the Big T. Time of day doesn’t seem to affect the fishing all that much either, especially in the summer and fall when they are feeding to store up for the long winter. The October caddis hatch is the best of the year, so a fall visit to the Big T. is recommended for best results. Bear in mind that crowds will be at their peak in the summer and fall, but you can find isolated pockets with fast fishing if you are willing to hike a bit further off the beaten path.

Best Flies for Big Thompson River

The major hatches on the Big Thompson River are midges, BWOs, caddis, stoneflies, and even some tricos here and there. Be sure to match the hatch as best you can, and check with a local shop before setting out to ensure you’ve got what you need.

Here are the recommended flies listed by order of importance.

- Hopper (tan #8-10)
- Elk Wing Caddis (dark #14,#16,#18
- CDC Loopwing Quill Emerger (baetis #16-22
- Rosenbauer Parachute Beetle (peacock #10 - 18)
- Smith's Crippled Emerger (salt and pepper #20-24)
- CDC Emerging Caddis (dark brown#16)
- Pheasant Tail Nymph (dark #18)
- Caddis pupas (dark #14-18)
- Prince Nymph (peacock #12- 20)
- Midge pupa (black #18 - 26)

Need flies? 

Ventures Fly Co. offers a great selection of dry flies, nymphs and streamers that will catch fish just about anywhere.  Set includes 40 high quality, hand-tied flies (see list below) and waterproof fly box. 

Dry Flies
- Adams Dry Fly
- Elk Hair Caddis
- Blue Wing Olive
- Royal Wulff
- Griffith's Gnat White
- Stimulator, Organge
- Chernobyl Ant

Nymphs/Wet Flies
- Rubber Leg Nymph, Brown
- BH Pheasant Tail Nymph
- BH Prince Nymph
- BH Hare's Ear Nymph
- Barr's Emerger Nymph
- Zebra Midge Nymph, Black

Streamers
- Wooly Bugger, Black (Size #8x2)
- Wooly Bugger, Olive (Size #8x2)

Big Thompson River Fishing Tips

Experts recommend a 8-1/2 foot 4-weight fly rod for the Big T.  Definitely pack your chest high waders. The water is cold year round thanks to its mountainous headwaters, so be prepared to layer up, too.

Need Gear? 

Below are recommendations for essential gear to make the most of your time on the water.

Quality rod, reel, line and rod tube at a reasonable price. Backed by Orvis 25-yr guarantee, a brand you can trust.

High performance nylon leader, great for fishing Dry Flies, Nymphs and Streamers.

Excellent knot strength, stretch and suppleness make this the finest nylon tippet.  3-pack of the sizes you'll need the most.

Heavy duty, waterproof, yet breathable.  If you are tough on waders, these are for you. Backed by Simms Wader Warranty. If they leak, they got your back.

Most durable, yet comfortable, boot on the market.  Excellent foot and ankle support.  Great for rocky rivers. Lightweight and designed for all-day wear.

Sweet pack with ample storage. Unique harness system reduces neck strain. Sleek tapered face improves visibility - you can see your feet when wading!

Durable and lightweight. The carbon fiber frame floats.  Hooks don't get stuck in the rubber mesh bag . Extra length makes it easier to net fish.  Simply the best nets on the market.

Tough, waterproof and priced right. Hold 900+ flies in slotted foam.  If you need more storage - you have too many flies!

Simple, sharp nippers at great price. Clip on retractor keeps this must have gear at your fingertips.

Strong with a fine tip. Perfect for removing split shot and hooks. Simply the best fishing pliers.

The 580 Glass polarized lenses are super clear and somehow relaxing on the eyes.  Game changer.

Note: DIY Fly Fishing earns a commission (at no cost to you) on sales made using the links above. Thank you for your support!

Big Thompson River Fishing Reports

Big Thompson River Fishing Regulations

Standard Colorado Division of Wildlife regulations apply to the majority of the river, but there is a Catch-and-Release only stretch for 9 miles below Lake Estes all the way to the Waltonia Bridge, and only artificial flies and lures are permitted on this section of the river. 

Big Thompson River Trip Planning Tips

Access to the Big Thompson River is only a 2 hour drive northwest of Denver, and you can fine ample accommodations of every variety in Boulder, Estes Park, Loveland, and Grand Lake. You can even camp right in Moraine Park if you don’t mind roughing it for a few days. There are also numerous hunting and fishing cabin rentals available in the surrounding area. Don’t forget to check out vacation rentals if you visit during the off-season for skiing either, as you can sometimes snag an unexpected bargain on a place to stay by renting a ski chalet or lodge when bookings are less frequent.

Looking for more places to fish? Visit our DIY Guide to the Best Fly Fishing in Colorado.


Feature image by Wusel007

About the author

Ken is an avid fisherman of 40+ years who loves to explore and find new places to fish. He created DIY Fly Fishing to help you do the same.

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