Crawford County Lake Quality
Iowa, 2 lakes, average grade D (Poor)
Crawford County has 2 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. On average, Crawford County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
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. Nelson Lake (D) is the cleanest in the county.
Quick Answers for Crawford County
Planning a trip? Check special fishing regulations for Nelson Lake — or check the official Iowa fishing regulations.
All Lakes in Crawford County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nelson Lake | D | 3.8 ft | - |
| 2 | Yellow Smoke Lake | D | 3 ft | - |
Other Counties in Iowa
See how Crawford 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 Crawford County
Top-rated places to stay near Crawford County
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Source: EPA National Aquatic Resource Surveys, 2026.