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LakeQuality
C

Park County Lake Quality

Montana, 1 lakes, average grade C (Fair)

Only 1 lakes in Park County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. Park County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.

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. Nla Lake (C) is the cleanest in the county.

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All Lakes in Park County

RankLakeGradeClarityPhosphorus
1Nla LakeC5.6 ft59.3 µg/L

See how Park County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 34 states.

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Source: EPA National Aquatic Resource Surveys, 2026.