Jefferson County Lake Quality
Wisconsin, 8 lakes, average grade C (Fair)
Only 8 lakes in Jefferson 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. Jefferson 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.
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 Rock Lake (B); the most-stressed is Mud Lake (D).
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Quick Answers for Jefferson County
Planning a trip? Check special fishing regulations for Rock Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
Fishing in Jefferson County
DNR Reports (4)
Wisconsin DNR Fisheries Survey resources for lakes in Jefferson County. browse all reports →
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2025Lower Spring Lake spring shocking survey, 2025Spring Shocking Survey · WI DNR · 2025 (PDF)
- 2023Lake Ripley comprehensive survey, 2023Comprehensive Survey · WI DNR · 2023 (PDF)
- 2023Lower Spring Lake Spring summary report, 2023Fisheries Survey · WI DNR · 2023 (PDF)
- 2022Rock Lake comprehensive survey, 2022Comprehensive Survey · WI DNR · 2022 (PDF)
All Lakes in Jefferson County
8 lakes · 7 graded, 1 not rated7 graded lakes · 1 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Max Depth | Access |
|---|---|---|---|---|---|---|---|---|
| 1 | BRock LakeJefferson | B | 12 ft | 18.1 µg/L | No recent samples | No recent samples | 60 ft | ✓ Public |
| 2 | BRed Cedar LakeJefferson | B | 4 ft | 23.4 µg/L | No recent samples | No recent samples | 6 ft | ✓ Public |
| 3 | BLake RipleyJefferson | B | 9 ft | 21.8 µg/L | No recent samples | No recent samples | 44 ft | ✓ Public |
| 4 | BBlue Spring LakeJefferson | B | 6.2 ft | 24.7 µg/L | No recent samples | No recent samples | 27 ft | ✓ Public |
| 5 | CLower Spring LakeJefferson | C | 4 ft | 44.1 µg/L | No recent samples | No recent samples | No recent samples | ✓ Public |
| 6 | DMud LakeJefferson | D | 2.3 ft | 63.6 µg/L | No recent samples | No recent samples | 22 ft | ✓ Public |
| 7 | DLake KoshkonongJefferson | D | 1.7 ft | 287 µg/L | No recent samples | No recent samples | 7 ft | ✓ Public |
| NRHope LakeJefferson | NR | 8 ft | No recent samples | No recent samples | No recent samples | 24 ft | Not recorded |
NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
Lake Match
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Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Other Counties in Wisconsin
See how Jefferson County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 39 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.