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

Park County Lake Quality

Colorado, 11 lakes, average grade C (Fair)

Park County holds 11 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. 2 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. 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.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Antero Reservoir (C); the most-stressed is Elevenmile Reservoir (D).

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All Lakes in Park County

11 lakes · 2 graded, 9 not rated2 graded lakes · 9 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
1CAntero ReservoirParkC14.8 ft15 µg/L1.1 µg/LNo recent samplesNot recorded
2DElevenmile ReservoirParkD13.1 ft33 µg/L5.5 µg/LNo recent samples✓ Public
NRMontgomery ReservoirParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRJefferson LakeParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLininger LakeParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRTarryall ReservoirParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRMilligan LakesParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRComo LakeParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRSpinney Mountain ReservoirParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRLake GeorgeParkNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBayou Salado ReservoirParkNRNo 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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Source: EPA National Aquatic Resource Surveys, 2026.