Colorado River
The upper Colorado River between Granby and Kremmling flows through a scenic valley of cottonwoods and willows in Grand County, offering Gold Medal trout fishing in a relatively uncrowded setting. This is big water with diverse opportunities, from walk-and-wade fishing in the Hot Sulphur Springs area to outstanding float trips through Byers Canyon and the ranch country downstream.
Current Conditions
Overview
The Colorado River, the legendary waterway that carved the Grand Canyon, begins as a modest mountain stream high on the Continental Divide in Rocky Mountain National Park. By the time it reaches the Grand County valley between Granby and Kremmling, it has grown into a substantial river that supports one of Colorado's finest Gold Medal trout fisheries.
The Gold Medal designation covers the river from the confluence with the Fraser River west of Granby downstream to its confluence with Troublesome Creek, approximately 4 miles east of Kremmling. This roughly 30-mile stretch flows through a beautiful high-altitude valley at about 7,600 feet elevation, flanked by cottonwood-lined banks, willow thickets, and open ranch land with mountain vistas in every direction.
Unlike Colorado's technical tailwaters, the upper Colorado River is a big, friendly river that welcomes anglers of all skill levels. The water has a classic freestone character with some tailwater influence from upstream reservoirs. The river is wide enough to accommodate both wade anglers and float boats without conflict, and public access is generous through several State Wildlife Areas and the Hot Sulphur Springs area.
Byers Canyon, a 4-mile stretch of tight, fast pocket water just west of Hot Sulphur Springs, offers a dramatically different character from the valley sections. The river drops through a narrow rock canyon with heavy-duty pocket water, deep plunge pools, and challenging wading.
The float fishing on the upper Colorado is among the best in the state, with multiple put-in and take-out options. The Pumphouse to Radium section is particularly popular, combining Gold Medal fishing with class I-II rapids in a beautiful canyon setting.
Water Characteristics
The upper Colorado River has classic freestone character with some tailwater moderation from upstream reservoir releases. Water clarity varies seasonally; during runoff (mid-May through late June), the river runs high, fast, and turbid with snowmelt. Once clearing begins, visibility improves to 3-6 feet in most sections, with some of the slower pools offering 8-10 feet of visibility by late summer. The water never achieves gin-clear tailwater conditions, which actually works in the angler's favor; trout are generally less leader-shy and more willing to eat.
Water temperatures follow a seasonal curve from near-freezing in winter to the mid-50s in late summer, with optimal trout feeding temperatures (48-58 degrees F) prevailing from late June through early October. The river's substrate is predominantly cobble and gravel, supporting outstanding insect habitat, particularly for stoneflies, caddis, and mayflies. The cottonwood and willow corridor provides critical shade, bank structure, and terrestrial insect habitat. The river also supports a healthy population of forage fish (sculpin and dace), making streamer fishing viable year-round.
Wading & Float Guide
The upper Colorado River is a big river by Colorado standards, and wading requires respect and preparation. In the valley sections near Hot Sulphur Springs, the river is typically 50-80 feet wide with a cobble-and-gravel bottom. During normal summer flows (300-600 cfs), much of the river is wadeable for careful anglers, with depths ranging from mid-thigh in the riffles to chest-deep in the runs and pools. Felt soles or studded boots are strongly recommended, and a wading staff provides essential stability.
Byers Canyon is a different proposition entirely. The river narrows dramatically and accelerates through a rock-walled gorge, with deep plunge pools, powerful currents, and a boulder-strewn bottom. Wading here is challenging and potentially dangerous for inexperienced anglers. Stay close to the banks and avoid crossing the river in the canyon.
The sections below Hot Sulphur Springs through ranch country offer the most comfortable wading. The river broadens, the gradient lessens, and gravel bars provide easy access to prime fishing water. However, spring runoff (typically mid-May through late June) can make the river unfishable, as flows can exceed 2,000 cfs.
Hot Sulphur Springs to Byers Canyon
A gentle float through the valley above Byers Canyon with excellent access to Gold Medal water. Shallow riffles, long glides, and productive bank water. Class I rapids only. Good for anglers new to float fishing.
Pumphouse to Radium
The most popular float section on the upper Colorado. Gold Medal water with class I-II rapids, diverse holding water, and beautiful canyon scenery. Half-day trip. Strong population of brown trout along undercut banks and in deep pools.
Radium to Rancho del Rio
Continuation of the canyon float with similar character to Pumphouse-Radium. Slightly lower fishing pressure and more remote feel. Class I-II rapids with some larger wave trains at higher flows.
Rancho del Rio to State Bridge
The river opens up through ranch country with long, productive runs and deep bank pools. Less whitewater than upstream sections. Excellent streamer water and hopper-dropper fishing in summer and fall.
State Bridge to Catamount
The furthest downstream section of premium fly fishing water. Class II-III rapids including the notable Catamount Falls area. Remote setting with fewer anglers. Good brown trout population in deep pools.
Rod & Tackle Guide
Hot Sulphur Springs / Valley Wade Sections
- Rod
- 9' 5-weight
- Line
- Weight-forward floating
- Leader & Tippet
- 9' tapered to 4X or 5X
Versatile all-around setup. The river is big enough to handle a 5-weight comfortably, and the heavier rod helps control larger nymph rigs and cut through the wind that often funnels through the valley.
Byers Canyon
- Rod
- 9' 5-weight or 6-weight
- Line
- Weight-forward floating
- Leader & Tippet
- 7.5-9' tapered to 3X or 4X
Heavier tippet is fine in the turbulent, less-clear canyon water. Shorter leader helps turn over larger stonefly and attractor patterns. Bring weighted nymph rigs for the deep plunge pools.
Float Trips (Pumphouse to State Bridge)
- Rod
- 9' 5-weight or 6-weight
- Line
- Weight-forward floating; bring a sink-tip for streamer work
- Leader & Tippet
- 9' tapered to 3X or 4X for hoppers/dries; 4' of heavy fluoro for streamers
Two-rod setup is ideal: one rigged for hopper-dropper, one for streamers. The 6-weight handles wind, big flies, and streamer casting more comfortably on the bigger water.
Seasonal Fishing Guide
Spring
Early April can offer excellent fishing before runoff begins, with BWO hatches on overcast afternoons and midge activity on sunny mornings. Nymphing with stonefly patterns, caddis larvae, and San Juan Worms is productive as trout feed aggressively after the lean winter months. By mid-May, snowmelt pushes the river into full runoff mode, and flows can exceed 2,000 cfs. Watch the USGS gauge (09034500) carefully; the window between ice-out and runoff can be as short as 3-4 weeks in a high snowpack year.
Summer
Summer is the crown jewel season on the upper Colorado. Runoff typically subsides by late June, and the river comes into prime shape with clearing water and warming temperatures that trigger prolific hatches. The PMD hatch is the signature summer event, producing consistent dry fly fishing from mid-morning through early afternoon. Caddis emergences light up the evenings, and Golden Stonefly activity near Byers Canyon provides opportunities for large attractor dries. This is prime hopper-dropper season. The best dry fly action is typically from 10 AM to 2 PM for mayflies and from 6 PM to dark for caddis.
Fall
Fall transforms the upper Colorado into a brown trout angler's paradise. As cottonwoods turn gold along the banks and the summer crowds vanish, large brown trout begin their spawning migration, moving out of deep pools and into shallower gravel runs. BWO hatches become the dominant surface activity, with best action on cloudy days between noon and 3 PM. Streamer fishing comes into its own as browns become aggressive and territorial; swing olive or brown Woolly Buggers and Sculpzilla patterns through deep banks and pool tailouts. By November, ice begins to form along the margins.
Fishing Pressure & Local Tips
The upper Colorado River receives moderate fishing pressure compared to the Front Range tailwaters. Its relative remoteness, approximately 2 hours from Denver via Interstate 70 and Highway 40, discourages casual day-trippers and keeps the angler-per-mile ratio manageable. The float sections distribute pressure effectively, as drift boats and rafts cover miles of water rather than concentrating in one spot. On summer weekends, the Pumphouse put-in can be busy, but once on the water, encounters with other boats are infrequent.
The wade-access sections at Hot Sulphur Springs and the State Wildlife Areas see the most concentrated pressure, particularly from mid-July through mid-September. The best strategy for avoiding pressure is to float, guided or self-guided, which provides access to miles of lightly-fished water between put-in and take-out points. Weekday fishing in September and October offers the ideal combination of excellent conditions and minimal competition.
Local Knowledge
The upper Colorado rewards a "cover water" approach more than the technical tailwaters. Rather than camping on one pool and working over a single fish, move steadily upstream or downstream, making a few good casts to each likely holding spot before moving on. Brown trout here are opportunistic feeders that respond well to a well-presented fly on the first drift.
For float trips, the hopper-dropper rig is king from July through September. Use a high-floating foam hopper (size 8-10) as both your indicator and a potential meal, with a beadhead nymph trailing 18-24 inches below. Cast tight to the banks, within 12 inches if possible. Local fly shops (Kirk's Flyshop in Estes Park/Grand Lake and the Mountain Angler in Breckenridge/Dillon) maintain current fishing reports. The USGS gauge at Hot Sulphur Springs (09034500) is the key reference: optimal wade fishing occurs at 200-500 cfs, while float fishing is comfortable at 300-1,200 cfs.
Species Present
Rainbow Trout
The rainbow trout is Montana's most widespread and popular gamefish, celebrated for its explosive surface strikes, aerial acrobatics, and willingness to take a well-presented dry fly. Native to Pacific Coast drainages from Alaska to Mexico, rainbows were first introduced to Montana's waters in the late 1800s and have since established thriving populations in nearly every major river system in the state. On legendary waters like the Madison, Missouri, and Bighorn, wild rainbow trout grow fat on prolific insect hatches and provide some of the finest dry-fly fishing in North America. Rainbow trout in Montana display remarkable variation depending on their home water. Fish in nutrient-rich tailwaters like the Missouri River below Holter Dam can exceed 20 inches with regularity, their deep bodies and broad tails reflecting the abundant food supply. Freestone river rainbows, such as those in the upper Madison and Gallatin, tend to be leaner and more athletic, shaped by faster currents and colder water temperatures. In many Montana rivers, rainbows spawn in the spring from March through June, and anglers should be mindful of spawning redds during this period to protect future generations of fish. Rainbows are arguably the most versatile trout species for fly anglers. They respond well to dry flies during hatches, aggressively chase streamers, and feed heavily on nymphs subsurface throughout the year. Their fighting ability is legendary: a hooked rainbow will often launch itself completely out of the water multiple times during a battle. Montana's catch-and-release regulations on many blue-ribbon streams have produced exceptional rainbow trout fisheries with high densities of large, healthy fish that continue to draw anglers from around the world.
Brown Trout
The brown trout is the most cunning and elusive trout species swimming in Montana's rivers, and it rewards patient, skilled anglers with some of the state's most memorable catches. Originally native to Europe and western Asia, brown trout were first introduced to North American waters in 1883 and arrived in Montana shortly thereafter. They have since established robust, self-sustaining populations in virtually every major trout stream in the state, from the legendary spring creeks of the Paradise Valley to the sweeping runs of the lower Madison and the deep pools of the Bighorn. Brown trout grow larger than any other trout species in Montana, and fish exceeding 24 inches are caught with regularity on premium waters. The lower Madison River, the Missouri River below Holter Dam, and the Bighorn River are particularly renowned for producing trophy-class browns. Unlike rainbows, brown trout spawn in the fall (October through November), and their aggressive pre-spawn behavior creates an exciting window for streamer fishing as large males become territorial and attack anything that enters their domain. Browns are notably more nocturnal than other trout species, and many of the biggest fish are caught during low-light conditions. What sets brown trout apart from other species is their wariness and selectivity. Large browns are notoriously difficult to fool, often refusing flies that are even slightly off in size, color, or presentation. They tend to establish and defend prime feeding lies (undercut banks, logjams, deep pools, and boulder gardens), and an angler who learns to read water and identify these holding spots will consistently catch more and larger fish. This combination of difficulty, size potential, and intelligence makes the brown trout the most prized quarry for many serious Montana fly fishers.
Mountain Whitefish
The mountain whitefish is one of Montana's most abundant native salmonids and arguably the most underappreciated gamefish in the state. A member of the whitefish subfamily (Coregoninae) within the broader salmonid family, mountain whitefish are present in virtually every cold-water river and large stream in Montana, often outnumbering trout by significant margins. On rivers like the Madison, Gallatin, Yellowstone, and Bitterroot, whitefish populations can exceed 1,000 fish per mile, making them the dominant salmonid species by biomass in many reaches. Despite this abundance, most fly anglers overlook whitefish entirely or view them as an unwelcome catch, which is unfortunate because they can provide outstanding sport on light tackle. Mountain whitefish are an important ecological component of Montana's river systems. They serve as a primary food source for larger brown trout, bald eagles, ospreys, otters, and other predators. Their fall spawning behavior (typically October through December) plays a critical role in nutrient cycling, and their eggs provide food for other fish and aquatic invertebrates during the lean winter months. In recent years, whitefish populations have been used as indicator species for overall river health, and declines in whitefish numbers on some Montana rivers have raised concerns about changing water conditions and disease pressure. For anglers willing to target them intentionally, mountain whitefish offer several advantages. They feed actively throughout the winter months when trout fishing can be slow, they are abundant and widely distributed, and they fight with surprising strength for their size; a 16-inch whitefish on a 3- or 4-weight rod provides a memorable tussle. Whitefish are also excellent table fare, with firm, mild-flavored white flesh that is delicious smoked or fried. Montana regulations typically allow a generous harvest limit for whitefish, recognizing their abundance and the role that harvest can play in managing populations on some waters.
Hatch Chart
| Insect | Suggested Fly | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Blue-Winged Olive (Baetis) afternoon | Parachute Adams | ||||||||||||
Blue-Winged Olive (Baetis) afternoon | BWO Emerger | ||||||||||||
Pale Morning Dun morning | Sparkle Dun | ||||||||||||
Caddisflies (various) evening | Elk Hair Caddis | ||||||||||||
Golden Stonefly all day | Stimulator | ||||||||||||
Terrestrials (hoppers, beetles) afternoon | Chubby Chernobyl | ||||||||||||
Midges morning | Zebra Midge | ||||||||||||
Stonefly nymphs (various) all day | Pat's Rubber Legs |
Blue-Winged Olive (Baetis): Spring BWOs before runoff. Size 16-20. Overcast afternoons are best.
Blue-Winged Olive (Baetis): Fall BWOs are the dominant surface activity. Size 18-20.
Pale Morning Dun: The signature summer hatch. Consistent dry fly fishing 10 AM to 2 PM. Size 16-18.
Caddisflies (various): Evening caddis emergences light up the river. Size 14-18.
Golden Stonefly: Golden stone activity near Byers Canyon. Size 8-12.
Terrestrials (hoppers, beetles): Prime hopper-dropper season. Cast tight to banks. Size 8-12.
Midges: Year-round midge activity, important in spring and fall. Size 18-24.
Stonefly nymphs (various): Subsurface stonefly nymphs productive pre-runoff. Size 8-12.
Recommended Flies
Chubby Chernobyl
Top PickPrimary dry fly for float trips; hopper-stimulator hybrid July through September
Best in summer
Pat's Rubber Legs
Top PickWorkhorse stonefly nymph, deadly as point fly in tandem rigs
Best in spring
Elk Hair Caddis
Top PickEssential during summer evening caddis hatches
Best in summer
Sparkle Dun
Top PickMatches the signature PMD hatch from late June through August
Best in summer
Parachute Adams
Top PickUniversal mayfly pattern, effective during PMD and BWO hatches
Best in summer
Woolly Bugger
Top PickClassic streamer for probing deep banks and pools for fall browns
Best in fall
San Juan Worm
Top PickConsistent producer in high water and early season
Best in spring
Curated Fly Boxes
Colorado River Summer Box
SummerCaddis-heavy selection for the Colorado River's outstanding summer hatches, with stonefly attractors for the canyon sections and reliable nymph patterns for prospecting.
Access Points & Boat Launches
Hot Sulphur Springs SWA
Wade AccessEasyState Wildlife Area providing excellent walk-in wade access to Gold Medal water in the Hot Sulphur Springs area. The Paul Gilbert Day Use Area and Lone Buck Unit offer well-maintained trails to the river with catch-and-release regulations. This is some of the most productive and accessible wade fishing on the upper Colorado.
Pumphouse Recreation Site
Boat LaunchEasyThe most popular put-in for float trips on the upper Colorado River. BLM-managed site with a developed boat ramp for drift boats and rafts. The 7-mile float from Pumphouse to Radium is the signature upper Colorado experience, combining Gold Medal fishing with class I-II rapids in a scenic canyon. Summer weekends can be busy at the ramp.
Radium Recreation Site
Boat LaunchEasyTake-out for the popular Pumphouse float and put-in for the Radium to Rancho del Rio section. State-managed site with a concrete boat ramp and ample parking. Good wade access both upstream and downstream of the ramp for anglers who prefer to fish on foot. The water near Radium holds good brown trout in the deeper runs.
Rancho del Rio
Boat LaunchEasyMid-river access point serving as both a take-out from Radium and put-in for the float to State Bridge. Private campground and outfitter operation with a well-maintained boat ramp. Good wade access to the surrounding river with productive runs and deep bank pools holding brown trout.
Regulations
Regulations
Fraser River confluence to Troublesome Creek (Gold Medal section): Byers Canyon to Troublesome Creek: artificial flies and lures only, catch-and-release for all trout. Hot Sulphur Springs State Wildlife Area: artificial flies and lures only, catch-and-release for all trout. Other sections within Gold Medal water: regulations vary by specific reach, some sections allow limited harvest. Colorado fishing license required. Open year-round, though practical season is April through November. Verify current regulations at cpw.state.co.us/fishing.
Always verify current regulations with Colorado Parks and Wildlife before fishing.
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Quick Facts
- Region
- Grand County / Northern Mountains
- Water Type
- Freestone
- River Length
- 1,450 miles total; ~30 miles of prime fly fishing from Granby to Kremmling
- Difficulty
- Beginner-Intermediate
- Best Seasons
- spring, summer, fall
- Trout Per Mile
- 2,000-3,500 in Gold Medal section
- Record Trout
- Brown trout exceeding 24 inches caught regularly; occasional fish over 8 lbs reported
- Species
- Rainbow Trout, Brown Trout, Mountain Whitefish
- USGS Gauge
- 09034500
Local Shops & Guides
Frying Pan Anglers
Basalt, CO
Frying Pan Anglers is a full-service fly shop and guide service located in Basalt, Colorado, at the confluence of the Frying Pan and Roaring Fork rivers. Established in 1986, the shop has served as the Roaring Fork Valley's premier fly fishing resource for nearly four decades, offering expert knowledge of the Frying Pan River tailwater, the Roaring Fork River, and the Colorado River. The shop stocks a complete selection of flies, rods, reels, waders, and accessories with a particular emphasis on the patterns and gear needed for the Frying Pan's famously technical tailwater fishing. The Frying Pan River below Ruedi Reservoir is renowned for its prolific midge and PMD hatches, and Frying Pan Anglers carries the specialized flies and fine tippet that success on this water demands. Their staff provides detailed, honest advice and their fishing reports are a trusted resource for anglers planning trips to the valley. Frying Pan Anglers' guide service covers the Frying Pan tailwater, Roaring Fork River, and Colorado River, offering both float and walk-wade trips. Their professional guides are intimately familiar with the seasonal patterns, hatches, and techniques that produce on each of these distinct fisheries. Whether you're nymphing tiny midges on the Frying Pan or floating hoppers along the banks of the Roaring Fork in late summer, their guides can put you in the right place with the right fly.
(970) 927-3441
Taylor Creek Fly Shops
Basalt, CO
Taylor Creek Fly Shops is a well-established fly fishing outfitter located in Basalt, Colorado, serving anglers who fish the Roaring Fork Valley's exceptional trout waters. The shop provides a full-service retail experience with quality gear, flies, and accessories, along with a professional guide service that covers the Frying Pan River, Roaring Fork River, and Colorado River. The shop's location in Basalt Center Circle puts it at a natural crossroads for anglers heading to the Frying Pan tailwater upstream or the Roaring Fork and Colorado rivers downstream. Taylor Creek carries a comprehensive fly selection tuned to local hatches, along with rods, reels, lines, waders, and accessories from leading brands. Their staff is friendly and knowledgeable, offering practical advice based on current conditions and years of experience on valley waters. Taylor Creek's guide service offers both float and wade trips for anglers of all skill levels. Their experienced guides know the nuances of each river — from the technical midge fishing on the Frying Pan to the big water of the Colorado — and can tailor trips to match each angler's goals and abilities. The shop also provides fly fishing instruction, making it a great resource for newcomers to the sport as well as experienced anglers visiting the Roaring Fork Valley for the first time.
(970) 927-4374
Where to Stay
Hot Sulphur Springs
A small, quiet town right on the Colorado River with natural hot springs that are perfect for soaking after a day of fishing. Limited but charming lodging options put you steps from excellent wade fishing water.
The hot springs resort is the main attraction for non-anglers in your group. Excellent wade access to the river right through town. Book ahead in summer; limited rooms fill fast.
Kremmling
A ranching and recreation hub at the confluence of the Colorado and Blue Rivers. The gateway to the Pumphouse to State Bridge float and the upper Colorado River canyon sections. Basic services with a western character.
Best base for the Pumphouse float section. Kremmling Anglers fly shop has the latest river reports. The town is small but has everything you need for a fishing trip: motels, a general store, and a few restaurants.