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LakeQuality
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Tomahawk Lake

Bayfield County, WisconsinOligotrophic

Tomahawk Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 30 puts Tomahawk Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake bottoms out at 42 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 131 acres, Tomahawk Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Tomahawk Lake sits at rank 39 of 55 in Bayfield County, in the lower half of the local distribution.

Tomahawk Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. The fishery includes walleye alongside the lake's other 4 documented species — a notable draw for Wisconsin anglers. A documented public access point at Tomahawk 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 2023-08-23. Grade methodology: LakeGrade methodology.

Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Crystal clear, you can see 45.9 ft down. Phosphorus level: 10.8 µg/L. Trophic State Index: 30.

MetricValueGrade
Water Clarity (Secchi Depth)45.9 ftA
Phosphorus10.8 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)30Oligotrophic

Low nutrients, clear water, excellent for swimming

Lake Details

CharacteristicValue
Maximum Depth42 ft
Surface Area131 acres
Public AccessYes

Fish Species

Click a species to see all Wisconsin and Minnesota lakes where it is found.

→ Best fishing times for Tomahawk Lake (14-day solunar calendar)

→ Is it safe to eat fish from Tomahawk Lake? (mercury & PFAS guide)

Tomahawk Lake fishing regulations (limits, seasons, special rules)

Invasive Species

Banded Mystery SnailEurasian Water-Milfoil

Water Quality Trend: Improving

Based on 4 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Improving+2.415 m/yr4

Recreation & Access

1
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #39 of 55 lakes in Bayfield County

Nearby Lakes in Bayfield County

State Parks Near Tomahawk Lake

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. 4 stations on file (most recent sample 2025).

Fish Species (DNR-rated)

Panfish(Common)Largemouth Bass(Common)Northern Pike(Common)Walleye(Present)

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

Most recent sample: 2023-08-23

Monitoring stations: 1