Linn County Lake Quality
Kansas, 10 lakes, average grade C (Fair)
Only 10 lakes in Linn 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. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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 Linn Valley Lake (B); the most-stressed is Marais des Cygnes Nwr Lake (F).
Quick Answers for Linn County
Planning a trip? Check special fishing regulations for Linn Valley Lake — or check the official Kansas fishing regulations.
All Lakes in Linn County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Linn Valley Lake | B | 8.2 ft | - |
| 2 | Parker City Lake | B | 6.2 ft | - |
| 3 | Pleasanton Reservoir | B | 4.3 ft | 22 µg/L |
| 4 | Blue Mound City Lake | C | 4.9 ft | 34.5 µg/L |
| 5 | Critzer Lake | C | 6.6 ft | - |
| 6 | Marais des Cygnes Wildlife Area Lake | C | 0.5 ft | 2.3 µg/L |
| 7 | Mound City Lake | C | 3.6 ft | 50 µg/L |
| 8 | Nla Lake | D | 2.3 ft | 47000 µg/L |
| 9 | La Cygne Lake | D | 2.4 ft | 37 µg/L |
| 10 | Marais des Cygnes Nwr Lake | F | 0.6 ft | 810 µg/L |
Other Counties in Kansas
See how Linn County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 34 states.
Where to stay near Linn County
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Source: EPA National Aquatic Resource Surveys, 2026.