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LakeQuality

Ml-Peterson Lake vs Outlet of Onamia Lake on the Rum River

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

Outlet of Onamia Lake on the Rum River has a higher water quality grade (A, Excellent) than Ml-Peterson Lake (B, Good). Both are in Mille Lacs County, Minnesota.

Ml-Peterson Lake and Outlet of Onamia Lake on the Rum River are both in Minnesota — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. The grades are close: Ml-Peterson Lake (B) and Outlet of Onamia Lake on the Rum River (A) are within one letter of each other on the LakeGrade rubric. The per-parameter sub-grades below will show where the small differences actually live.

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.

B

Ml-Peterson Lake

Mille Lacs County, Minnesota

Moderate clarity, visible to about 7.4 ft.

A

Outlet of Onamia Lake on the Rum River

Mille Lacs County, Minnesota

No clarity data.

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.

MetricMl-Peterson LakeOutlet of Onamia Lake on the Rum River
Overall GradeB (Good)A (Excellent)
Water Clarity7.4 ftNo data
Phosphorus26.5 µg/L25 µg/L
Chlorophyll-a (Algae)3.9 µg/L0.6 µg/L
Maximum Depth42 ft10 ft
Surface Area128.3K acres1.0K acres
Public AccessYesNo
Fish Species10
Trophic Statemesotrophicoligotrophic

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

Verdict

Outlet of Onamia Lake on the Rum River wins on overall water quality with a Grade A versus Ml-Peterson Lake's Grade B. For more fish-species variety, Ml-Peterson Lake edges ahead with 1 documented species.