Lake John is a cold, clear oligotrophic lake in Jackson County, Colorado. Water quality is graded B based on 1 sampling years through 2025. Compared to the 3 other monitored lakes in Jackson County, Lake John ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Colorado DNR, last sampled 2025-09-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 13.8 ft. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.8 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
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Fishing Lake John
Location
County Ranking
Ranked #3 of 4 lakes in Jackson County
Nearby Lakes in Jackson County
Explore Lake John across LakeGrade
More Colorado Lake Rankings
Other Grade B Lakes in Colorado
Oligotrophic Lakes in Colorado
More records, surveys & data sources
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-09
Monitoring stations: 1