
Hancock County Lake Quality
Iowa, 6 lakes, average grade F (Algae-prone)
Hancock County holds 6 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.
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 Crystal Lake Max Depth (F); the most-stressed is Crystal Lake Max Depth (F).
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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
6 lakes · 2 graded, 4 not rated2 graded lakes · 4 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | FCrystal Lake Max DepthHancock | F | 1.6 ft | 99 µg/L | 50.3 µg/L | No recent samples | ✓ Public |
| 2 | FEldred Sherwood LakeHancock | F | 3 ft | 89 µg/L | 31.3 µg/L | No recent samples | Not recorded |
| NRLake GeorgeHancock | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NREagle LakeHancock | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NREast Twin LakeHancock | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRWest Twin LakeHancock | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public |
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 Iowa
See how Hancock 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.