Mildred Lake
Oneida County, WisconsinOligotrophic
Mildred Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Oneida County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
A TSI value of 37 puts Mildred Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. A maximum depth of 45 ft puts Mildred Lake in the middle of Wisconsin's depth distribution. At 168 acres, Mildred Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Mildred Lake ranks 9 of 134 in Oneida County, putting it in the upper tier of locally monitored lakes.
Mildred Lake has at least one documented invasive species (Chinese Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Walleye are documented at Mildred Lake, one of 4 fish species on record for the lake. A documented public access point at Mildred Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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 2025-08-24. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 18.5 ft down. Phosphorus level: 10.7 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 18.5 ft | A |
| Phosphorus | 10.7 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 45 ft |
| Surface Area | 168 acres |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
→ Best fishing times for Mildred Lake (14-day solunar calendar)
→ Is it safe to eat fish from Mildred Lake? (mercury & PFAS guide)
→ Mildred Lake fishing regulations (limits, seasons, special rules)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.707 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.32 µg/L/yr | 6 |
Recreation & Access
Location
County Ranking
Ranked #9 of 134 lakes in Oneida County
Nearby Lakes in Oneida County
More Wisconsin Lake Rankings
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
Oligotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1992. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2025-08-24
Monitoring stations: 1
Where to stay near Mildred Lake
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