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LakeQuality
C

Franklin County Lake Quality

Wisconsin, 1 lakes, average grade C (Fair)

Franklin 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. Franklin County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.

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. Gmw-07 Lake (C) is the cleanest in the county.

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All Lakes in Franklin County

RankLakeGradeClarityMax DepthPhosphorus
1Gmw-07 LakeC4.8 ft--

Source: EPA National Aquatic Resource Surveys, 2026.