St. Croix County Lake Quality
Wisconsin, 5 lakes, average grade C (Fair)
St. Croix County has 5 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 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. Lake St Croix (B) is the cleanest in the county.
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Quick Answers for St. Croix County
Planning a trip? Check special fishing regulations for Lake St Croix, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
Fishing in St. Croix County
DNR Reports (9)
Wisconsin DNR Fisheries Survey resources for lakes in St. Croix County. browse all reports →
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2025Cedar Lake comprehensive spring survey, 2025Comprehensive Survey · WI DNR · 2025 (PDF)
- 2025Hatfield Lake spring shocking survey, 2025Spring Shocking Survey · WI DNR · 2025 (PDF)
- 2025Lake George spring survey, 2025Fisheries Survey · WI DNR · 2025 (PDF)
- 2025Little Falls Lake spring shocking survey, 2025Spring Shocking Survey · WI DNR · 2025 (PDF)
- 2025Twin Lakes northern pike stocking assessment survey, 2025Fisheries Survey · WI DNR · 2025 (PDF)
- 2024Apple Lake spring survey, 2024Fisheries Survey · WI DNR · 2024 (PDF)
- 2021Cedar Lake spring survey, 2021Fisheries Survey · WI DNR · 2021 (PDF)
- —Population assessment of lake sturgeon in the upper St. Croix River, Minnesota and Wisconsin 2003-2011Fisheries Survey · WI DNR (PDF)
- —St. Croix River catfish survey, 2020-2024Fisheries Survey · WI DNR (PDF)
All Lakes in St. Croix County
5 lakes5 graded lakes
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Max Depth | Access |
|---|---|---|---|---|---|---|---|---|
| 1 | BLake St CroixSt. Croix | B | 5.6 ft | 30 µg/L | No recent samples | No recent samples | 60 ft | ✓ Public |
| 2 | BBass LakeSt. Croix | B | 10 ft | 14 µg/L | No recent samples | No recent samples | No recent samples | ✓ Public |
| 3 | BBass Lake Pump SiteSt. Croix | B | No recent samples | 14.5 µg/L | No recent samples | No recent samples | 33 ft | ✓ Public |
| 4 | DApple LakeSt. Croix | D | 2.5 ft | 84.9 µg/L | No recent samples | No recent samples | 32 ft | ✓ Public |
| 5 | DLake MallalieuSt. Croix | D | 2.8 ft | 53.5 µg/L | No recent samples | No recent samples | 17 ft | ✓ Public |
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 St. Croix 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.