Blue Stream Fly Fishing
Fly Fishing Report for:

South Boulder Creek - Below Gross Reservoir - Colorado

Hatch Chart - Best Access/Spots - Local Fish - About

Water Flow Chart

Using Water Flow Charts & Weather Reports: Begin with our water flow charts to grasp stream velocity and volume – look for stable or rising trends to pinpoint ideal fishing times. Learn to interpret sudden spikes or drops, which can indicate potential challenges. Next, consult our weather reports to understand ambient conditions. Pairing the two, you can anticipate fish behavior, choose the right gear, and select the best fishing spots. Use these tools together for a holistic approach to your next fishing adventure.

In-Depth Weather

Directions To Location

Hatch Chart

Month Hatch Time of Day Recommended Fly Sizes Popular Fly Patterns
January Midge Afternoon #18-26 Zebra midges, RS2s
February Midge Afternoon #18-26 Griffith's Gnats, Black Beauties
March Midge, Blue-winged Olive Mid-late Afternoon #16-26 BWO emergers, Zebra midges
April Blue-winged Olive Mid-Afternoon #18-20 BWO Parachute
May Caddis, Stonefly Afternoon, Evening #8-22 Elk Hair Caddis, Foam Back Emerger
June Stonefly, Green Drake Afternoon, Dusk #8-22 Stimulator, Green Drake Dries
July Caddis, Stonefly, PMD Morning, Evening #14-24 Elk Hair Caddis, Foam Back PMD
August Caddis, Trico Morning, Evening #16-26 Trico Spinner, IDYLWILD Foam Caddis
September Trico, Midge Morning, Afternoon #20-26 Griffith's Gnats, Trico Duns
October Blue-winged Olive, Midge Late Morning, Afternoon #16-26 BWO emergers, Bunny Midges
November Midge Afternoon #18-26 Rojo Midge, Disco Midge
December Midge Afternoon #18-26 Zebra midges, Palomino Midge

While we strive to ensure the precision of our hatch charts, some reflect broader river region insights. Through ongoing partnerships with local guides and fly shops, we’re committed to refining our data. Should you notice any inconsistencies or have feedback, we welcome you to reach out. 

Best Fishing Spots

The South Boulder Creek – Below Gross Reservoir is a haven for fly fishing enthusiasts. The waters of this creek teem with Rainbow trout, Brown trout, and Cutthroat trout, making it a perfect spot for fly fishing. The best fishing locations in this region include:

  • Walker Ranch: This large park area provides an abundance of fly fishing opportunities. The creek meanders through the park allowing for various fishing spots.
  • Canyon Mouth: This point, where the creek leaves the canyon and enters the grassy plains, is home to larger fish species.
  • Gilpin Bridge: A preferred spot among locals, this accessible location is populated with abundant fish.

It’s crucial to check fishing conditions and regulations before venturing out, as seasonal changes can affect accessibility and the types of fish present.

Best Access Points

The South Boulder Creek – Below Gross Reservoir offers some of the best fly fishing in Colorado. Here are some top access points worth checking out:

  • Walker Ranch Park: It provides a well-marked, easy-to-follow trail down to the creek.
  • Osprey Point: Situated near the east end of Gross Reservoir, from here, anglers can hike downhill to reach the creek.
  • South Boulder Creek Trail: Fly fishers opt this trail for multiple access points along its course. While the 3-mile hike may be strenuous, the exceptional fishing spots it uncovers are copious.

Remember, as with all fly fishing locations, access points may require hiking and maneuvering through uneven terrain. Always tread lightly to avoid damaging highly-sensitive riverbanks and take care to respect private property where applicable.

Local Fish

  • Brown Trout: This fish is a popular choice among fly fishermen due to its abundant population in the South Boulder Creek. They are known for their aggressive behavior, making them a fun and challenging catch.
  • Rainbow Trout: These vibrant fish are not just a sight to behold but also a preferred catch among fly fishermen. They are usually a lot easier to catch compared to Brown Trout.
  • Brook Trout: While less common in the South Boulder Creek, Brook Trout still remain a prized catch. These fish inhabit the cooler, higher-altitude sections of the creek.
  • Cutthroat Trout: Native to Colorado, Cutthroat Trout offer a rewarding catch due to their rarity. They inhabit parts of the South Boulder Creek and are easily identifiable by their vivid coloration and the distinctive red “cutthroat” mark below their jaw.
  • Mountain Whitefish: A relative of the trout, Mountain Whitefish are abundant in the South Boulder Creek. Their bottom-feeding habits make them a challenging catch on the fly, but their large population ensures plenty of opportunities to try.
  • Greenback Cutthroat Trout: A subspecies of Cutthroat Trout, Greenback Cutthroat Trout are listed as threatened. Hence, they are primarily catch-and-release to preserve their population.
  • Colorado River Cutthroat: Though less common, the Colorado River Cutthroat offers a unique catch for fly fishermen in the South Boulder Creek.
  • Golden Trout: Considered the Holy Grail among fishermen, Golden Trout are highly elusive. Catching one is considered a milestone in a fly fisherman’s career.

About The River

The South Boulder Creek – Below Gross Reservoir has an enticing history worth exploring. Its unique journey starts in the high country west of Rollinsville and traces an 80-mile path toward the plains of Boulder, Colorado.

Since its humble beginnings, the creek has played a significant role in the area’s development. Pioneers first utilized the creek for farming purposes. Later, the reservoir was established, which increased the creek’s importance, offering a crucial supply of fresh water to the swiftly growing communities.

One amusing chapter from the creek’s history occurred in the 1850s. A mini gold rush ensued when traces of gold were discovered in the area! Fortunately, this didn’t disrupt the picturesque beauty of the creek.

  • The bountiful fish populations attract anglers from around the country, providing fantastic opportunities for fly fishing.
  • Your adventure along the South Boulder Creek isn’t completed without exploring the encircling hiking trails, offering breathtaking vistas of beautiful Colorado.

As time flows, much like the waters of the South Boulder Creek, this precious piece of natural history remains a beloved part of the local landscape.


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