Big Green River
Wisconsin · Driftless Area — Grant County, Northwest of Fennimore
Brown TroutRainbow Trout
Top 5 Fishing Locations on the Big Green River
Catch and Release Section — Hwy T to Hwy 133
The Category 5 catch-and-release stretch between County Highway T and State Highway 133 is the best water on the Big Green. Tackle busters live in here — browns that have spent years growing in protected water with excellent insect life and no harvest pressure. Artificial only, catch-and-release only. The DNR maintains public fishing easements through this section so access is good. Fish the shaded pools and runs along the undercut banks. This is the section that makes anglers come back to the Big Green year after year.
💧 Ideal flow: spring-fed and stable. The catch-and-release section fishes best at low stable flows when clarity is high and fish are visible. Mornings and evenings in this section are the only times the larger fish move openly — midday fish tuck tight to cover.
Upper River — Spring Valley Road Area
The DNR public fishing easement runs from Spring Valley Road downstream to Highway 133, giving continuous legal access through the best stretches. The upper section near Spring Valley Road flows through open pasture with good spring input that keeps temperatures down even in summer. Harvest regulations apply upstream of Highway T with a slot limit of 10 to 13 inches — a management strategy designed to protect the larger fish while allowing some harvest of smaller ones. The open banks here make for straightforward casting.
💧 Ideal flow: the spring-fed upper section runs cool and clear year-round. Check conditions after significant rain — the Big Green can run a bit off-color after heavy storms but clears faster than freestone streams. Best fished in spring before temperatures climb.
Highway K Corridor — Main Access Stretch
Green River Road and County Highway K run alongside the Big Green for most of its 11 managed miles, providing the easiest access to the river. Multiple road crossings and town roads give entry points throughout this corridor. The river here is classic Driftless spring creek — pools connected by riffles, averaging 15 feet wide with some 25-foot-wide pools in the lower sections. Habitat improvement work including lunker structures is visible throughout this section and the fish density reflects that work.
💧 Ideal flow: good across a range of conditions. The highway corridor is easy to check from the road before committing to a section. Avoid sections that look off-color after heavy rain and move to clearer water further upstream toward the spring heads.
Wooded Sections — Off the Beaten Path
Where the Big Green transitions from open pasture into wooded areas the casting gets harder and the fish get easier. Canopy shade keeps the water cooler in summer and the wooded sections see less pressure than the open meadow stretches visible from the road. Browns in the shade are less wary. Several large springs feed the Big Green from the wooded hillsides and the cold spring inputs create temperature refuges that concentrate fish in summer heat. Worth working through the brush for a few good fish.
💧 Ideal flow: the wooded sections stay cooler in summer than open meadow sections. Fish these particularly in July and August when open sections warm up midday. Look for the spring seeps and coldwater inputs — fish stack up at temperature breaks on warm days.
Lower River — Approach to Wisconsin River
The Big Green arises from gushing springs in Grant County and rushes to the nearby Wisconsin River. The lower sections of the river widen slightly and can hold larger fish that have moved downstream. Access becomes tighter on the lower stretch as DNR easements thin out — scout access points before wading through private land. Fall is when the lower river really shines as brown trout stage and become aggressive before their spawn. The wider lower pools are the best bet for the largest fish in the system.
💧 Ideal flow: the lower river warms more quickly in summer than the spring-fed upper sections. Best fished in spring and fall. Summer fishing is still productive near spring inputs but midday lower river fishing in July and August can be slow when temps push into the upper 60s.
About Big Green River Fishing
The Big Green River starts from a series of gushing springs in Grant County, Wisconsin, and flows through open pastures and meadows northwest of Fennimore before reaching the Wisconsin River. Eleven miles of it is managed as a Class I wild brown trout fishery — self-sustaining, no stocking. The Category 5 catch-and-release section between County Highway T and State Highway 133 is where the trophy fish live. Open banks make casting straightforward — this is a good first Driftless stream for anglers transitioning from western freestone rivers. The fish are technical, the water is clear, and a good presentation with the right pattern matters more than covering distance.
Best Time to Fish the Big Green River
Spring from opening day through June is the prime window. Insect hatches are consistent and the water is cold and clear from winter. Fall is arguably the best overall. Brown trout get aggressive in September and October, the crowds thin out, and the fish move more freely than in summer. Summer fishing is good near the spring inputs and in the shaded wooded sections but the open meadow sections can warm midday in July and August. Fish early and late. The Big Green has year-round hatches including good sulphur activity in spring and summer and reliable caddis through the season.
Species
Brown trout dominate the entire managed stretch. Rainbow trout show up occasionally. Some stocking has occurred in portions of the river historically but the stream is managed primarily as a wild brown trout fishery. The catch-and-release section holds the largest browns in the system. Natural reproduction has improved considerably over the years through habitat restoration work by the DNR and conservation volunteers.
Access and Regulations
The DNR maintains public fishing easements from Spring Valley Road downstream to Highway 133. The Category 5 catch-and-release section from County Highway T to State Highway 133 requires artificial lures only. Upstream of Highway T the harvest slot limit is 10 to 13 inches. Fish outside that slot must be released. Check current Wisconsin DNR regulations for season dates and full rules before fishing. Wisconsin trespass law allows wading navigable streams with legal entry. The Driftless Angler fly shop in Viroqua and area fly shops near Fennimore are the best resources for current conditions.
Live River Data
Streamflow data is pulled in real time from the USGS National Water Information System where available. The Big Green is spring-fed and stable through most of the season. Check conditions after significant rain before making the drive — the creek can run off-color after heavy storms though it typically clears within a day or two.