Bass Lake
St. Croix County, WisconsinMesotrophic
Bass Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in St. Croix County. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.
The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Within St. Croix County's 5 graded waters, Bass Lake sits at rank 1, near the top of the local distribution.
No invasive species are currently listed at Bass Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Bass Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-04-22. Grade methodology: LakeGrade methodology.
Watch Bass Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 10 ft. Phosphorus level: 14 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10 ft | B |
| Phosphorus | 14 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.246 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.8 µg/L/yr | 6 |
Recreation & Access
Location
County Ranking
Ranked #1 of 5 lakes in St. Croix County
Nearby Lakes in St. Croix County
More Wisconsin Lake Rankings
State Parks Near Bass Lake
Other Grade A Lakes in Wisconsin
Washington County · Clarity: 11.8 ft
Washington County · Clarity: 12.6 ft
Walworth County · Clarity: 11 ft
Waukesha County · Clarity: 11.3 ft
Walworth County · Clarity: 20.2 ft
Kenosha County · Clarity: 10 ft
Mesotrophic Lakes in Wisconsin
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2026-04-22
Monitoring stations: 2
Where to stay near Bass Lake
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