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F

Comus Lake

Walworth County, WisconsinHypereutrophic

Comus Lake earns an F: 193 µg/L of phosphorus and clarity at 1.5 ft signal heavy nutrient loading from the surrounding watershed. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The hypereutrophic status — TSI 76 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. A maximum depth of just 6 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. Comus Lake covers 131 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within the 35 graded lakes of Walworth County, Comus Lake sits at rank 32, near the bottom of the county list.

No invasive species are currently listed at Comus Lake — the lake remains off the Wisconsin infested-waters roster. Bass fishing is part of the appeal: the species list runs to 3, anchored by largemouth and/or smallmouth bass. A documented public access point at Comus 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 2021-08-24. Grade methodology: LakeGrade methodology.

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Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 1.5 ft of visibility. Phosphorus level: 193 µg/L. Trophic State Index: 76.

MetricValueGrade
Water Clarity (Secchi Depth)1.5 ftF
Phosphorus193 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)76Hypereutrophic

Very high nutrients, dense algae, poor clarity

Lake Details

CharacteristicValue
Maximum Depth6 ft
Surface Area131 acres
Public AccessYes

Fish Species

Click a species to see every graded lake where it is documented.

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

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

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

Water Quality Trend: Declining

Based on 2 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable0 m/yr2
Phosphorus Declining+113 µg/L/yr2

Recreation & Access

1
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #32 of 35 lakes in Walworth County

Cleaner Lakes Within 30 Miles

Comus Lake holds Grade F. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Walworth County

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. 1 station on file (most recent sample 2023).

Fish Species (DNR-rated)

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

Reservoir Info (USACE NID)

Comus Lake is a man-made reservoir impounded by the Delavan (completed 1947), built primarily for recreation on the TURTLE CREEK; gravity-type dam, 13 ft tall and 100 ft long.

Surface area
164 ac
Normal storage
606 ac-ft
Max storage
850 ac-ft
Drainage area
67 sq mi
Hazard class
Low
Owner
City Of Delavan

Source: USACE National Inventory of Dams, NID ID WI00321 · Operator website

EPA Impairment Status

Comus Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Nutrients (phosphorus, nitrogen)

Source: EPA ATTAINS assessment unit WI10001424 · 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

Public boat-access points from the USGS National Boat Ramps inventory

Most recent sample: 2021-08-24

Monitoring stations: 1

Where to stay near Comus Lake

Compare lakeside cabins, hotels, and vacation rentals near Comus Lake in Walworth County, Wisconsin — live availability and prices for your trip.

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