South Boulder Creek Fly Fishing Report
Walker Ranch on South Boulder Creek, below Gross Reservoir. Daily Colorado DWR flow is an upstream reference, separate from Boulder Creek. Plan bank fishing: Boulder County currently prohibits wading. Check the sourced access notes and posted restrictions before hiking in.
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What's swimming in South Boulder Creek
- Rainbow Trout: Boulder County explicitly identifies Rainbow Trout fishing along South Boulder Creek at Walker Ranch, a different waterbody from Boulder Creek (Boulder County fishing locations).
- Brown Trout also live here: The county’s Walker Ranch fly-fishing article describes both Brown and Rainbow Trout, many in the 10- to 15-inch range. This is a 2017 description, not a current population survey or a claim that rainbows dominate (Boulder County Parks & Open Space).
- Season and releases matter: The county identifies spring through autumn as the best fishing period and warns that reduced winter releases from Gross Reservoir can make fishing difficult. Check this reach’s own flow and posted access rules before making the hike (Boulder County).
Getting to South Boulder Creek
This guide covers Walker Ranch below Gross Reservoir, not Boulder Creek or the reservoir shoreline. Plan to fish from legal banks: Boulder County currently lists swimming and wading as prohibited. The gauge is upstream of the fishing access, not a sensor at every pool.
- Walker Ranch Loop Trailhead: Boulder County lists 46 car spaces, two ADA spaces and a restroom. Follow the county trail map to South Boulder Creek and stay within the mapped public property. The full loop is 7.9 miles; that is not a required fishing approach distance (Boulder County Walker Ranch).
- Ethel Harrold Trailhead: An alternative county trailhead with 18 car spaces and a restroom. The county lists Ethel’s Trail as 0.6 miles; use its official map to plan the onward route rather than treating that number as the complete walk to the creek (Boulder County Walker Ranch).
- Parking and return hike: The county warns that the Walker Ranch Loop and Ethel Harrold lots are often full. Carry the official map, leave time for the climb out, and use designated parking only. Meyers Gulch may have parking, but do not assume it is an equivalent short fishing approach (Boulder County).
- Bank fishing and park hours: Boulder County’s current Parks & Open Space rules prohibit swimming and wading. Parks and trailheads open at sunrise and close at sunset; follow posted restrictions and do not park overnight (Boulder County regulations).
- Fishing at Walker Ranch: The county lists Rainbow Trout with a limit of four and permits artificial and live bait. A Colorado fishing license is required for anglers age 16 and older. Check current CPW rules and posted notices before fishing; this is not automatically catch-and-release-only water (Boulder County fishing rules).
- Gross Reservoir construction: Denver Water reports periodic restrictions on its South Boulder Creek Outlet Trail below the dam. That is a separate approach from the county trailheads; check current agency updates and do not interpret a reservoir-area closure as proof that all Walker Ranch access is closed or open (Denver Water access updates; Walker Ranch updates).
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4 fly pairings from real fishing reports
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Fly shops on South Boulder Creek
No fly shops in our directory are tagged to this river yet.
South Boulder Creek fly fishing questions
What is a good flow (cfs) to fish South Boulder Creek?
TroutTips uses a seasonal 100-125 cfs favorable-flow window from Rocky Mountain Anglers. A below-25-cfs caution is based on published winter low-release concerns, not an agency fishing closure or a universal threshold. Readings are daily Colorado DWR observations below Gross Reservoir, upstream of Walker Ranch. Neither the range nor a normal-flow label guarantees safe access: Boulder County prohibits wading, so plan bank fishing and check posted restrictions.
Is South Boulder Creek designated Gold Medal water?
No, South Boulder Creek does not currently carry Colorado Parks and Wildlife's Gold Medal water designation.
What flies work on South Boulder Creek?
TroutTips tracks 4 fly pairings reported specifically on South Boulder Creek, each tied to a season and a real source. See the Fly Pairings section on this page for the full list.