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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
F

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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All Lakes in Hancock County

6 lakes · 2 graded, 4 not rated2 graded lakes · 4 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
1FCrystal Lake Max DepthHancockF1.6 ft99 µg/L50.3 µg/LNo recent samples✓ Public
2FEldred Sherwood LakeHancockF3 ft89 µg/L31.3 µg/LNo recent samplesNot recorded
NRLake GeorgeHancockNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NREagle LakeHancockNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NREast Twin LakeHancockNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRWest Twin LakeHancockNRNo recent samplesNo recent samplesNo recent samplesNo 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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Source: EPA National Aquatic Resource Surveys, 2026.