Big Gunpowder Falls
Below Prettyboy Reservoir · Cockeysville
Baltimore County, Maryland, USA
Open live forecast →Target species: Brown and Rainbow.
Stream gauge: 01581500. Flow and water temperature update on every refresh.
Weekly AI Outlook as of 06/05/26
The Big Gunpowder is running at a skinny 4 cfs, forcing trout into deeper pockets and demanding precise presentations. With water temps in the mid-50s and morning air temps dropping to the upper 50s by week's end, expect classic June Trico spinner falls at first light—fish size 22-24 patterns on 7X tippet in the deeper runs. Sulphurs should emerge during evening hours as the 80+ degree afternoons warm the water. Focus on structure and avoid spooking fish in these crystal-clear, low conditions.
- Flow: 4 cfs — extremely low conditions concentrating fish in deeper holes. Stealth approach critical with ultra-clear water.
- Hatches: Trico spinners at first light, Sulphurs in evenings. Size 22-24 Trico patterns on 7X, CDC Sulphur #16 for evening rise.
- Water Temp: Mid-50s — ideal for both Trico and Sulphur activity. Cool enough to keep trout comfortable through warm afternoons.
- Best Window: Dawn for Trico spinner falls, then deep nymphing midday. Evening dry fly action as Sulphurs emerge around 7-8pm.
Generated weekly from live USGS gauge readings, weather forecasts, and recent fly shop reports. Updates Friday mornings.
About this Water
- Tailwater
- Best months: Year-round; best Apr–June and Sept–Oct. Peak: May (Sulphur hatch) and June (Trico)
The Big Gunpowder Falls below Prettyboy Reservoir is the finest tailwater trout fishery in the mid-Atlantic region — just 20 miles from Baltimore, the river holds exceptional populations of wild brown trout and produces outstanding evening Sulphur and Trico hatches throughout the season. The catch-and-release section from Falls Road to Prettyboy Road is managed by Maryland DNR as premier wild trout habitat. For mid-Atlantic anglers unable to reach New England or Appalachian waters regularly, the Big Gunpowder is a world-class fishery within an hour's drive.
The Big Gunpowder Falls' catch-and-release section holds wild brown trout population densities that rival western spring creeks — an extraordinary achievement just 20 miles from one of the East Coast's largest cities.
January Outlook
January on the Big Gunpowder Falls tailwater — the Mid-Atlantic's finest year-round trout fishery, just north of Baltimore. The Prettyboy Reservoir release maintains 44–50°F water all winter. Midge and scud nymphing in the beautiful gorge section, with no crowds and excellent wild trout access.
Productive Patterns
- Zebra Midge #20-22
- Scud (tan, olive)
- RS2
- Soft Hackle Midge
Tips
The Gunpowder is excellent in January. The C&R section from Falls Road to Masemore Road bridge holds exceptional wild rainbow and brown trout in cold tailwater. Fish the slow seams and pool edges with midge nymphs on 6X–7X tippet. The gorge section is beautiful in winter snow — one of the Mid-Atlantic's finest year-round experiences.
Water Notes
Regulated 40–500 cfs. Water 44–50°F year-round from Prettyboy Reservoir. Year-round tailwater fishery north of Baltimore.
February Outlook
February on the Gunpowder. The Prettyboy Reservoir release continues maintaining consistent winter conditions. The Mid-Atlantic's finest tailwater is fishable every month — February midge nymphing in the gorge section produces wild rainbow and brown trout for dedicated anglers.
Productive Patterns
- Zebra Midge
- Scud
- WD-40
- Soft Hackle Midge
Tips
February fishing on the Gunpowder rewards those willing to brave Maryland winter. The gorge section above Masemore Road is sheltered from wind. Fish the slow pools with midge nymphs and scuds. Wild rainbows average 12–16 inches and are in excellent condition from year-round tailwater feeding. 6X–7X tippet in clear tailwater.
Water Notes
40–400 cfs. Water 44–50°F. Year-round tailwater conditions continue. Gorge section provides some shelter from winter wind.
March Outlook
March on the Gunpowder — the first hatches of the year in the Mid-Atlantic's finest tailwater gorge. Early Quill Gordon and Midge Dry hatches appear on mild afternoons. The tailwater's consistent temperatures allow hatches to begin weeks earlier than surrounding freestone streams.
Productive Patterns
- Quill Gordon #14-16
- Blue Winged Olive
- Midge Dry #22
- Soft Hackle
Tips
March brings the first surface activity to the Gunpowder. Quill Gordon hatches begin on afternoons above 50°F — typically mid-to-late March. The section from Falls Road to Masemore is the best early-spring water. The wild rainbows that have been nymphing all winter begin looking up. Position carefully in the clear tailwater — fish see you easily.
Water Notes
60–400 cfs. Water 46–52°F. Early spring conditions. Tailwater character produces early hatches.
April Outlook
The Big Gunpowder Falls below Prettyboy Reservoir in Maryland is the Mid-Atlantic's finest tailwater fishery. Hendrickson and Quill Gordon hatches for wild rainbow and brown trout.
Productive Patterns
- Hendrickson
- Quill Gordon
- Blue Winged Olive
- Soft Hackle Emerger
Tips
The Gunpowder's catch-and-release section from Falls Road to the Masemore Road bridge is the premier water. Wild rainbows average 12–16 inches with fish to 20 inches common. 5X tippet minimum.
Water Notes
Regulated 40–600 cfs. Water 44–52°F year-round from Prettyboy Reservoir.
May Outlook
Sulphur and March Brown season on the Gunpowder. One of the finest May dry fly experiences in the Mid-Atlantic.
Productive Patterns
- Sulphur Sparkle Dun
- March Brown
- Elk Hair Caddis
- PMD
Tips
The Gunpowder's evening Sulphur hatch is exceptional — one of the Mid-Atlantic's finest. The tight gorge sections above Masemore Road are beautiful and productive. Fish are selective but the hatches bring them to the surface.
Water Notes
80–400 cfs. Water 48–56°F. Excellent spring tailwater conditions.
June Outlook
Trico and Caddis season on the Gunpowder. The morning Trico spinner fall is the signature event on this Mid-Atlantic tailwater.
Productive Patterns
- Trico Spinner
- Elk Hair Caddis
- PMD Cripple
- Sulphur Dry
Tips
The Trico spinner fall on the Gunpowder begins at first light in June. Fish size 22–24 patterns on 7X tippet. The consistent tailwater flows make the Gunpowder one of the region's most reliable fisheries.
Water Notes
60–300 cfs. Water 50–58°F. Consistent tailwater conditions.
July Outlook
July on the Gunpowder tailwater. The Prettyboy Reservoir release maintains cool summer temperatures in the gorge while Maryland's piedmont heats up around it. Trico spinner falls at dawn are a signature Gunpowder experience. One of the Mid-Atlantic's few genuine July tailwater options.
Productive Patterns
- Trico Spinner #22-24 (dawn)
- Scud
- Zebra Midge
- Elk Hair Caddis (evening)
Tips
The Gunpowder Trico spinner fall is extraordinary in July — arrive before dawn and watch the cloud of insects gather. Fish size 22–24 patterns on 7X tippet in the flat pools. After Trico activity, switch to scud and midge nymphing. The gorge section is shaded and cooler than the surrounding piedmont. Fish morning and evening only.
Water Notes
40–300 cfs. Water 46–54°F. Cold tailwater in Maryland summer. Trico season at peak. Dawn fishing recommended.
August Outlook
August on the Gunpowder. The tailwater continues producing through Maryland's hottest month. Pre-dawn Trico spinner falls remain excellent. Scud and midge nymphing all day in the C&R section. One of the Mid-Atlantic's best summer tailwater destinations.
Productive Patterns
- Trico Spinner (pre-dawn)
- Scud
- Zebra Midge
- RS2
Tips
August on the Gunpowder is excellent for early risers. Be at Falls Road before 5:30am for the Trico spinner fall. The gorge section's natural shade helps in August heat. The wild rainbows and browns in this tailwater are in excellent condition from year-round scud and midge feeding. 6X–7X tippet always.
Water Notes
40–280 cfs. Water 44–52°F. Year-round tailwater. Pre-dawn Trico fishing excellent. Gorge shade helps in August heat.
September Outlook
Excellent fall fishing on the Gunpowder with reliable BWO hatches. One of the Mid-Atlantic's finest fall trout experiences.
Productive Patterns
- Blue Winged Olive
- Elk Hair Caddis
- Trico Spinner
- Streamer
Tips
Fall on the Gunpowder is outstanding. The consistent tailwater temperatures and reliable hatches continue through October. Brown trout become aggressive before spawning. A beautiful gorge setting with fall foliage.
Water Notes
60–400 cfs. Cooling 48–56°F. Excellent fall tailwater conditions.
October Outlook
October on the Gunpowder — one of the Mid-Atlantic's finest fall experiences. Pre-spawn brown trout are aggressive, BWO hatches are reliable, and the gorge section displays spectacular autumn color. The year's best dry fly conditions for large wild browns.
Productive Patterns
- Blue Winged Olive #18-20
- Mahogany Dun
- Streamer (olive)
- Copper John
Tips
October is the Gunpowder's finest month. Pre-spawn wild brown trout are aggressive and the BWO hatch is reliable on overcast afternoons. Fish streamers for the largest browns in the morning, then switch to dry flies during hatch windows. The gorge section in October colors is spectacular. The Gunpowder is at its best.
Water Notes
60–400 cfs. Cooling 46–54°F. Outstanding fall conditions. The Gunpowder's finest month.
November Outlook
November on the Gunpowder. Brown trout spawning and reliable late-season midge and scud fishing. The gorge section in late fall with no crowds and reliable year-round tailwater conditions — one of the Mid-Atlantic's best November trout streams.
Productive Patterns
- Midge Nymph
- Scud
- Egg Pattern (small)
- BWO (early month)
Tips
November is excellent on the Gunpowder. Spawning brown trout in the upper sections. Fish egg patterns below redds. Late BWO activity on mild afternoons continues through mid-November. The consistent tailwater temperatures mean late-season fishing is nearly as productive as spring. One of Maryland's finest year-round streams.
Water Notes
50–400 cfs. Cooling 44–52°F. Year-round tailwater. Brown trout spawning season. Late season excellent.
December Outlook
December on the Big Gunpowder completes a full year of tailwater fishing. The Prettyboy Reservoir release maintains 44–50°F water through winter and midge nymphing produces wild trout year-round in one of the Mid-Atlantic's finest gorge settings. A worthy December destination near Baltimore.
Productive Patterns
- Zebra Midge
- Scud
- RS2
- Soft Hackle Midge
Tips
December on the Gunpowder is excellent for year-round tailwater enthusiasts. The gorge section is beautiful in snow with no other anglers. Fish the slow pools with midge nymphs and scuds on 6X–7X tippet. Wild rainbows and browns are active in cold tailwater. One of the finest year-round tailwater fisheries in the eastern US.
Water Notes
40–400 cfs. Water 44–50°F year-round. Year-round tailwater fishery. December solitude in the Mid-Atlantic's finest gorge.
Hatch Calendar
| Insect | Peak | Active | Size | Productive Patterns |
|---|---|---|---|---|
| Blue Winged Olive Baetis spp. |
Apr, Oct | Mar, Apr, May, Sep, Oct, Nov | #18–22 |
|
| Sulphur Ephemerella dorothea |
May, Jun | May, Jun | #16–18 |
|
| Midge Chironomidae |
Jan, Feb, Mar, Dec | Jan, Feb, Mar, Apr, Oct, Nov, Dec | #22–26 |
|
Access & Approach
Cockeysville and Phoenix, MD area (Baltimore County). Maryland fishing license required. Special regulations apply to the C&R section. MDNR releases from Prettyboy Reservoir — check conditions. Multiple fly shops in the Baltimore area serve this fishery.
Nearby Fly Shops
- Backwater Angler
- Fish Talk Magazine
- Relentless Fly Fishing
Regulations & License
Fishing in Maryland requires a current license. Always verify season dates, bag limits, and any special-regulation waters before you fish.
Maryland fishing regulations & license →
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About Current
Big Gunpowder Falls conditions on Current combine real-time flow data (USGS, WSC, CDEC, CEHQ), weather, tide predictions, hatch probabilities calibrated to this specific water, and recent fly shop reports from the area.
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