Washington County Lake Quality
Iowa, 1 lakes, average grade F (Very Poor)
Washington County has 1 graded 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. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
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 Darling Max Depth (F); the most-stressed is Lake Darling Max Depth (F).
Quick Answers for Washington County
Planning a trip? Check special fishing regulations for Lake Darling Max Depth — or check the official Iowa fishing regulations.
All Lakes in Washington County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Lake Darling Max Depth | F | 1.6 ft | - |
Other Counties in Iowa
See how Washington County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near Washington County
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Source: EPA National Aquatic Resource Surveys, 2026.