Ozaukee County Lake Quality
Wisconsin, 9 lakes, average grade B (Good)
Ozaukee County has 9 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. With an average grade of B, Ozaukee County sits comfortably above the Wisconsin median.
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 Sandhill Lake (B); the most-stressed is Sandhill Lake (B).
Where to stay near Ozaukee County
Top-rated places to stay near Ozaukee County
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Ozaukee County?
Get lake water-quality report cards plus the best cabin & lodging deals near Ozaukee County — straight to your inbox. No spam, unsubscribe anytime.
Quick Answers for Ozaukee County
Planning a trip? Check special fishing regulations for Sandhill Lake — or browse the full Wisconsin regulations index.
Fishing in Ozaukee County
All Lakes in Ozaukee County
9 lakes · 1 graded, 8 not rated1 graded lake · 8 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Max Depth | Access |
|---|---|---|---|---|---|---|---|---|
| 1 | BSandhill LakeOzaukee | B | 7.5 ft | 24.7 µg/L | No recent samples | No recent samples | 9 ft | Not recorded |
| NRSpring LakeOzaukee | NR | 2.5 ft | No recent samples | No recent samples | No recent samples | 22 ft | Not recorded | |
| NRUnnamed LakeOzaukee | NR | No recent samples | 12.2 µg/L | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCty E PondOzaukee | NR | 3.7 ft | 33.6 µg/L | No recent samples | No recent samples | 6 ft | Not recorded | |
| NRWatts LakeOzaukee | NR | 7 ft | 43.1 µg/L | No recent samples | No recent samples | 31 ft | Not recorded | |
| NRThiensville MillpondOzaukee | NR | No recent samples | 166 µg/L | No recent samples | No recent samples | No recent samples | ✓ Public | |
| NRGrafton MillpondOzaukee | NR | No recent samples | 110 µg/L | No recent samples | No recent samples | No recent samples | ✓ Public | |
| NRHawthorne Hills PondOzaukee | NR | No recent samples | 57.6 µg/L | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMoldenhauer LakeOzaukee | NR | No recent samples | 12.2 µg/L | No recent samples | No recent samples | 32 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
Which lake suits how you actually use one?
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 Ozaukee 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.