Marion County Lake Quality
Oregon, 1 lakes, average grade B (Good)
Only 1 lakes in Marion 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-wide average lands at B — solid water quality with most lakes carrying clear summer transparency and low-to-moderate phosphorus.
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 Detroit Lake (B); the most-stressed is Detroit Lake (B).
Quick Answers for Marion County
Planning a trip? Check special fishing regulations for Detroit Lake — or check the official Oregon fishing regulations.
All Lakes in Marion County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Detroit Lake | B | - | 20 µg/L |
Other Counties in Oregon
See how Marion County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 27 states.
Where to stay near Marion County
Top-rated places to stay near Marion County
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Source: EPA National Aquatic Resource Surveys, 2026.