F
Decatur County Lake Quality
Indiana, 1 lakes, average grade F (Very Poor)
Decatur 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.
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. a leading lake (—) is the cleanest in the county.
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Quick Answers for Decatur County
All Lakes in Decatur County
| Rank | Lake | Grade | Clarity | Phosphorus |
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Source: EPA National Aquatic Resource Surveys, 2026.