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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
NR

Ravalli County Lake Quality

Montana, 21 lakes — no lake here has enough monitoring data for a grade

There are 21 monitored lakes in Ravalli County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. No lake in Ravalli County has enough sampling behind it for an A–F grade yet. The 21 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.

Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.

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All Lakes in Ravalli County

21 lakes · 0 graded, 21 not rated0 graded lakes · 21 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
NRSouth Fork LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBig Creek LakesRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRSouth Kootenai LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBass LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBurnt Fork LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRFred Burr ReservoirRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMill LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBlodgett LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHigh LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRCanyon LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLower Twin LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRFish LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLost Horse LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRElk LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBig Grizzly LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRKerlee LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLake ComoRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRPainted Rocks LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRBoulder LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRNelson LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRTin Cup LakeRavalliNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded

NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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See how Ravalli County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..

Source: EPA National Aquatic Resource Surveys, 2026.