Franklin Lake
Oneida County, WisconsinOligotrophic
Franklin 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.
Trophically, Franklin Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. The lake bottoms out at 25 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 159 acres, Franklin Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Franklin Lake ranks 7 of 134 in Oneida County, putting it in the upper tier of locally monitored lakes.
No invasive species are currently listed at Franklin Lake — the lake remains off the Wisconsin infested-waters roster. The fishery is bass-led, with 5 documented species across the lake's records. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-02. Grade methodology: LakeGrade methodology.
Watch Franklin Lake water quality
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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 16.2 ft down. Phosphorus level: 12.3 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.2 ft | A |
| Phosphorus | 12.3 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 25 ft |
| Surface Area | 159 acres |
Fish Species
Click a species to see every graded lake where it is documented.
→ Best fishing times for Franklin Lake (14-day solunar calendar)
→ Is it safe to eat fish from Franklin Lake? (mercury & PFAS guide)
→ Franklin Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.3 m/yr | 5 |
| Phosphorus | ↑ Improving | -0.26 µg/L/yr | 6 |
Location
County Ranking
Ranked #7 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 2001. 1 station on file (most recent sample 2026).
Fish Species (DNR-rated)
EPA Impairment Status
Franklin Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10026427 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Most recent sample: 2026-06-02
Monitoring stations: 1
Where to stay near Franklin Lake
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