Tailwater · Mixed Metamorphic · Maryland

Gunpowder Falls

A rocky pool on the Gunpowder Falls river surrounded by autumn foliage, with a large boulder in the foreground.

The Gunpowder below Prettyboy Dam is a small miracle — a seven-mile tailwater of wild brown trout half an hour north of downtown Baltimore.

Good · Brown Trout
Sulphur Comparadun · 16-18
Goodlive now
A proper day on the water
River steady at a fishable height. A proper day for it. Work the seams with an upstream nymph, switch to the dry when they show.
75% confidence
What moved it
  • Level0.48 mLast reading 23h ago
  • Water temp10.3°C
  • ClarityClear
Today's fly
SC
Sulphur Comparadun16-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
0.48 m
Last reading 23h ago
Water temp10.3°C
ClarityClear
Weather23°C
WindS 11 km/h
Pressure1017 hPa
Rain · recent9.5 mm
Rain · ahead0.0 mm

Live readings — water temperature is an estimate where the gauge does not record it.

Water temperature for Brown Trout
Ideal
10°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Good — water temperature is working for you, but time of day is the limiting factor today.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 3 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 3 guilds with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 3 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
2
2
2
2
2
1
SulphurHatch
2
3
2
Trico (Eastern)Hatch
2
3
3
2
Eastern Blue-Winged OliveHatch
2
3
3
3
3
3
3
3
2
Eastern Summer BWO (Drunella)Hatch
2
3
3
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
  • Maryland licence required; catch-and-release wild trout regulations on the tailwater reach — verify current MDNR rules and the fly-fishing-only sections.
What's coming
Plan ahead
5-day outlook
Gallery · 2
  1. A rocky pool on the Gunpowder Falls river surrounded by autumn foliage, with a large boulder in the foreground.
    Autumn Along the Gunpowder
  2. Terrain map of the venue
    Terrain map
About this water

The Gunpowder below Prettyboy Dam is a small miracle — a seven-mile tailwater of wild brown trout half an hour north of downtown Baltimore. Back in the eighties, Maryland's DNR and Trout Unlimited talked the dam operators into a guaranteed minimum cold release, and the browns took it from there; the river hasn't been stocked since, and it doesn't need to be. It's tight, technical, tree-lined water — sulphurs and caddis in season, midges and scuds the rest of the year, and trout that have seen every fly in the box. Read the release out of Prettyboy and fish small.

  • Mixed metamorphic
Water quality · US Clean Water Act
  • Aquatic life: Not assessed
What this classification means

EPA ATTAINS assessment unit 'Gunpowder Falls' (MD-02130805-Gunpowder_Falls), 2024 Integrated Report. Aquatic Life use: not assessed. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · MD-02130805-Gunpowder_Falls

The full read · show the working · for Brown Trout · confidence 75%
How the 79 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity49 × 12%5.9
Conditions total= 79
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Booking & contacts