Marshall County Lake Quality
Oklahoma, 3 lakes, average grade D (Nutrient-rich)
Marshall County has 3 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.
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 Lake Texoma (D); the most-stressed is Lake Texoma (D).
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Quick Answers for Marshall County
Planning a trip? Check special fishing regulations for Lake Texoma — or check the official Oklahoma fishing regulations.
All Lakes in Marshall County
3 lakes · 1 graded, 2 not rated1 graded lake · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | DLake TexomaMarshall | D | 1.7 ft | 142 µg/L | 23 µg/L | No recent samples | ✓ Public |
| NRHauani LakeMarshall | NR | 7 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCarter LakeMarshall | 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 Oklahoma
See how Marshall 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.