Linn County Lake Quality
Kansas, 11 lakes, average grade C (Fair)
Linn 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. Linn 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. Pleasanton Reservoir (C) is the cleanest in the county.
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Quick Answers for Linn County
Planning a trip? Check special fishing regulations for Pleasanton Reservoir — or check the official Kansas fishing regulations.
All Lakes in Linn County
11 lakes · 2 graded, 9 not rated2 graded lakes · 9 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | CPleasanton ReservoirLinn | C | 4.3 ft | 22.5 µg/L | 16 µg/L | No recent samples | ✓ Public |
| 2 | DMound City LakeLinn | D | 3.6 ft | 50 µg/L | 24 µg/L | No recent samples | Not recorded |
| NRBlue Mound City LakeLinn | NR | 4.9 ft | 34.5 µg/L | 8.3 µg/L | No recent samples | Not recorded | |
| NRCritzer LakeLinn | NR | 6.6 ft | 20 µg/L | 12.5 µg/L | No recent samples | Not recorded | |
| NRLinn Valley LakeLinn | NR | 8.2 ft | 20 µg/L | 4.2 µg/L | No recent samples | Not recorded | |
| NRMarais des Cygnes Nwr LakeLinn | NR | 0.6 ft | 810 µg/L | 255 µg/L | No recent samples | Not recorded | |
| NRLa Cygne LakeLinn | NR | 2.4 ft | 37 µg/L | 56 µg/L | No recent samples | ✓ Public | |
| NRParker City LakeLinn | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMarais des Cygnes Wildlife Area LakeLinn | NR | 0.5 ft | 2.3 µg/L | 454 µg/L | No recent samples | ✓ Public | |
| NRLake ChaparralLinn | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBoicourt LakeLinn | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not 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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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 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.