Siskiwit Lake
Bayfield County, WisconsinLimited DataMesotrophic
Siskiwit Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season.
A TSI near 50 places Siskiwit Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. A maximum depth of just 13 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. The lake's 285 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Siskiwit Lake ranks 41 of 52 in Bayfield County — at the lower end of the locally monitored distribution.
No invasive species are currently listed at Siskiwit Lake — the lake remains off the Wisconsin infested-waters roster. Walleye are documented at Siskiwit Lake, one of 5 fish species on record for the lake. 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 2022-09-19. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
No clarity data. Phosphorus level: 23.3 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 23.3 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 13 ft |
| Surface Area | 285 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Siskiwit Lake (14-day solunar calendar)
→ Is it safe to eat fish from Siskiwit Lake? (mercury & PFAS guide)
→ Siskiwit Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -0.75 µg/L/yr | 3 |
Location
County Ranking
Ranked #41 of 52 lakes in Bayfield County
Cleaner Lakes Within 30 Miles
Siskiwit Lake holds Grade B. One nearby lake has a higher grade.
Nearby Lakes in Bayfield County
More Wisconsin Lake Rankings
State Parks Near Siskiwit Lake
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 1 station on file (most recent sample 2024).
Fish Species (DNR-rated)
EPA Impairment Status
Siskiwit 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 WI10008910 · 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
Most recent sample: 2022-09-19
Monitoring stations: 2