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LakeQuality

Oldham Lake vs Willow Lake

Water quality, depth, fish species, and recreation comparison.

Oldham Lake and Willow Lake both received the same overall water quality grade of C (Fair). Both are in Wisconsin.

Both Oldham Lake and Willow Lake sit in Iowa. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. These two are within a letter of each other on the rubric — Oldham Lake (C) versus Willow Lake (C). The deciding factors for a recreational visitor are likely physical (depth, access, fish species) rather than water-quality differences.

With grades this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.

C

Oldham Lake

Monona County, Wisconsin

Murky, only visible to about 5.1 ft.

C

Willow Lake

Harrison County, Wisconsin

Murky, only visible to about 4.8 ft.

Side-by-Side Metrics

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

Source: EPA National Aquatic Resource Surveys, 2026.

MetricOldham LakeWillow Lake
Overall GradeC (Fair)C (Fair)
Water Clarity5.1 ft4.8 ft
PhosphorusNo dataNo data
Chlorophyll-a (Algae)8.5 µg/L9.5 µg/L
Maximum Depth--
Surface Area16.1 acres19 acres
Public AccessUnknownUnknown
Fish Species00
Trophic Stateeutrophiceutrophic

Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).

Verdict

Both lakes earn the same Grade C. The tiebreakers come down to clarity (Oldham Lake: 5.1 ft, Willow Lake: 4.8 ft) and what you want from the lake. Oldham Lake matches its peer on species count.