Milwaukee County Lake Quality
Wisconsin, 15 lakes, average grade C (Fair)
Milwaukee County's 15 graded lakes fall in the moderate-density bracket for Wisconsin. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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. Lakeshore State Park-Milwaukee (A) is the cleanest in the county.
Quick Answers for Milwaukee County
Planning a trip? Check special fishing regulations for Lakeshore State Park-Milwaukee, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in Milwaukee County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Lakeshore State Park-Milwaukee | A | 24.6 ft | - | - |
| 2 | Lakeshore State Park Fish Shocking | A | 26.2 ft | - | - |
| 3 | New Zoo Pond | A | 24.9 ft | - | - |
| 4 | Mallard Lake | A | 16.4 ft | 10 ft | - |
| 5 | Csmi 2015 Station Q Lake | A | - | - | - |
| 6 | Milwaukee Harbor Lake | C | 8.2 ft | - | - |
| 7 | Milwaukee Harbor Lake | C | 8.5 ft | - | - |
| 8 | Milwaukee Harbor Lake | C | 8.2 ft | - | - |
| 9 | Milwaukee Harbor Lake | C | 6.6 ft | - | - |
| 10 | Milwaukee River Lake | C | 4.9 ft | - | - |
| 11 | Milwaukee Harbor Lake | C | 7.5 ft | - | - |
| 12 | Milwaukee Harbor North Half Lake | C | 7.2 ft | - | - |
| 13 | Milwaukee Harbor South Half Lake | D | 7.4 ft | - | - |
| 14 | Milwaukee Harbor Estuary Lake | D | 3.9 ft | - | - |
| 15 | Milwaukee Harbor Lake | D | 6.6 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.