
Marion County Lake Quality
Texas, 9 lakes, average grade F (Algae-prone)
Marion County holds 9 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. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
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. Lake O the Pines Mid Lake (F) is the cleanest in the county.
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Quick Answers for Marion County
Planning a trip? Check special fishing regulations for Lake O the Pines Mid Lake — or check the official Texas fishing regulations.
All Lakes in Marion County
9 lakes · 2 graded, 7 not rated2 graded lakes · 7 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | FLake O the Pines Mid LakeMarion | F | 2.7 ft | 30 µg/L | 41.7 µg/L | No recent samples | ✓ Public |
| 2 | FLake OpinesMarion | F | 2 ft | 50 µg/L | 59.2 µg/L | No recent samples | ✓ Public |
| NRClinton LakeMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCaddo Lake Dwight Shellmans HomeMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public | |
| NRMonterey LakeMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRJohnson Creek ReservoirMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLittletons LakeMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRClear LakeMarion | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRClinton LakeMarion | 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 Texas
See how Marion 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.