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Big Lake reads lower on nutrients and algae than Three Island Lake. Both are in Beltrami County, Minnesota.

Reviewed by LakeQuality Editorial Team · Updated

Both Big Lake and Three Island Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any differences in the readings here are about the lakes themselves, not the agencies sampling them. The readings are close: Big Lake and Three Island Lake sit within a narrow band of each other on phosphorus, chlorophyll-a and clarity. The per-parameter table below shows where the small differences actually live.

With readings 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.

Big Lake

Beltrami County, Minnesota

Moderate clarity, visible to about 9.7 ft.

Three Island Lake

Beltrami County, Minnesota

Good clarity, visible to about 11.8 ft.

Side-by-Side Metrics

MetricBig LakeThree Island Lake
Water Clarity9.7 ft11.8 ft Better
Phosphorus15 µg/L Better17 µg/L
Chlorophyll-a (Algae)4.8 µg/L4.1 µg/L Better
Maximum Depth35 ft Better25 ft
Surface Area3,598 acres729 acres
Public AccessYesYes
Fish Species1717
Trophic Statemesotrophicmesotrophic

A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.

Verdict

Big Lake and Three Island Lake read the same on nutrients and algae overall. The tiebreakers come down to clarity (Big Lake: 9.7 ft, Three Island Lake: 11.8 ft) and what you want from the lake. Big Lake matches its peer on species count.

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Where to stay near Big Lake and Three Island Lake

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Source: EPA National Aquatic Resource Surveys, 2026.