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Fishing Union Reservoir: what the data says
749-acre reservoir near Weld County. The lake tops out around 28 ft. The contours are modeled from the water's real shoreline and maximum depth. Treat them as a rough guide, and never use them for navigation. Here is how the season plays out for each species, straight from the data behind the map.
Largemouth Bass fishing at Union Reservoir
Spring largemouth bass on Union Reservoir hold shallow, usually 2 to 10 ft. Summer pushes them deeper, 8 to 20 ft, and winter fish settle into 8 to 28 ft. Shallow bay flat is the standout, a weed flat at roughly 3 ft, rated prime for spring largemouth bass. Best bite is early morning and the evening. Tie on a texas-rigged 10" worm or a deep-diving crankbait and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 2 to 10 ft | dawn & dusk | Spinnerbait, Chatterbait |
| Summer | 8 to 20 ft | dawn & dusk | Texas-rigged 10" worm, Deep-diving crankbait |
| Fall | 4 to 15 ft | midday & dawn | Squarebill crankbait (shad), Spinnerbait |
| Winter | 8 to 28 ft | midday | Blade bait, Jigging spoon |
Smallmouth Bass fishing at Union Reservoir
Spring smallmouth bass on Union Reservoir hold shallow, usually 3 to 12 ft. They move out to 8 to 28 ft in summer and finish the year down in 8 to 28 ft. The spot to know is Main-lake point, a point in about 8 ft of water that rates prime for smallmouth bass in fall. Best bite is early morning and the evening. Tie on a drop shot (goby/minnow) or a ned rig and you're in the game.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | dawn & dusk | Ned rig, Tube jig |
| Summer | 8 to 28 ft | dawn & dusk | Drop shot (goby/minnow), Ned rig |
| Fall | 8 to 25 ft | midday & dawn | Jerkbait, Blade bait |
| Winter | 8 to 28 ft | midday | Blade bait, Hair jig |
White Bass & Hybrids fishing at Union Reservoir
Spring white bass & hybrids on Union Reservoir hold shallow, usually 3 to 15 ft. Summer pushes them deeper, 8 to 28 ft, and winter fish settle into 8 to 28 ft. The spot to know is Main-lake point, a point in about 8 ft of water that rates prime for white bass & hybrids in fall. Best bite is early morning and the evening. Summer baits: a jigging spoon or a topwater (when schooling) gets it done.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 15 ft | midday & dawn | Rooster tail / inline spinner, Curly-tail jig (white/chartreuse) |
| Summer | 8 to 28 ft | dawn & dusk | Jigging spoon, Topwater (when schooling) |
| Fall | 8 to 25 ft | midday & dawn | Small blade bait, Jigging spoon |
| Winter | 8 to 28 ft | midday | Jigging spoon, Blade bait (vertical) |
Common Carp fishing at Union Reservoir
In spring, common carp run shallow here, mostly 2 to 10 ft. Summer pushes them deeper, 3 to 15 ft, and winter fish settle into 8 to 28 ft. Shallow bay flat is the standout, a weed flat at roughly 3 ft, rated prime for spring common carp. Best bite is early morning and the evening.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 2 to 10 ft | midday & dawn | |
| Summer | 3 to 15 ft | dawn & dusk | |
| Fall | 5 to 18 ft | midday | |
| Winter | 8 to 28 ft | midday |
Channel Catfish fishing at Union Reservoir
Spring channel catfish on Union Reservoir hold shallow, usually 3 to 12 ft. They move out to 8 to 25 ft in summer and finish the year down in 8 to 28 ft. Deep basin is the standout, a deep basin at roughly 24 ft, rated prime for winter channel catfish. Best bite is after dark and the evening.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 3 to 12 ft | dusk | |
| Summer | 8 to 25 ft | night & dusk | |
| Fall | 8 to 28 ft | dusk | |
| Winter | 8 to 28 ft | midday |
Crappie fishing at Union Reservoir
In spring, crappie run shallow here, mostly 2 to 8 ft. They move out to 10 to 25 ft in summer and finish the year down in 8 to 28 ft. If you only fish one area, make it Deep basin: a deep basin around 24 ft that scores prime in winter. Best bite is early morning and the evening. Summer baits: a jig trolled/spider-rigged or a small crankbait (trolled) gets it done.
| Season | Depth | Best window | Go-to baits |
|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | 1/16 oz jig + tube, Curly-tail grub |
| Summer | 10 to 25 ft | dawn & dusk | Jig trolled/spider-rigged, Small crankbait (trolled) |
| Fall | 8 to 20 ft | dawn | Jig + minnow combo, Small swimbait (1.5-2") |
| Winter | 8 to 28 ft | midday | Tungsten jig + soft plastic, Tiny jigging spoon |
Union Reservoir also holds walleye (8 to 28 ft in summer), yellow perch (8 to 28 ft in summer), bluegill (4 to 15 ft in summer), rainbow trout (7 to 28 ft in summer). Pick any of them on the map above for rated spots and bait picks.
Notable structure
- Deep basin: deep basin, around 24 ft
- Break off the point: drop-off, around 13 ft
- Main-lake point: point, around 8 ft
- Secondary point: point, around 8 ft
- Shallow bay flat: weed flat, around 3 ft
- Back-bay flat: weed flat, around 3 ft
Common questions
How deep is Union Reservoir?
Union Reservoir is about 28 ft at its deepest point. The contours here are modeled from the water's real shape and maximum depth, so treat them as a rough guide.
What fish are in Union Reservoir?
Anglers target largemouth bass, smallmouth bass, walleye, crappie, bluegill, channel catfish, rainbow trout, white bass & hybrids, yellow perch, common carp on Union Reservoir.
Where is the best fishing spot on Union Reservoir?
Shallow bay flat is the top-rated area: a weed flat in about 3 ft of water that rates prime for largemouth bass in spring. Open the map above to see every rated spot for each species and season.
When is the best time to fish Union Reservoir?
For largemouth bass, the summer bite is best in early morning and the evening. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Nearby waters
Milavec Reservoir · Waneka Lake · Boulder City Reservoir · Lon Hagler Reservoir · Carter Lake · Boyd Lake
See how Union Reservoir stacks up: best largemouth bass lakes in Colorado · best smallmouth bass lakes in Colorado · best walleye lakes in Colorado · best crappie lakes in Colorado
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