Hancock County Lake Quality
Iowa, 2 lakes, average grade F (Very Poor)
Only 2 lakes in Hancock 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 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. Crystal Lake Max Depth (F) is the cleanest in the county.
Quick Answers for Hancock County
Planning a trip? Check special fishing regulations for Crystal Lake Max Depth — or check the official Iowa fishing regulations.
All Lakes in Hancock County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Crystal Lake Max Depth | F | 1.6 ft | - |
| 2 | Eldred Sherwood Lake | F | 3 ft | - |
Other Counties in Iowa
See how Hancock County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
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Source: EPA National Aquatic Resource Surveys, 2026.