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.
Watch Comus Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
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.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | F |
| Phosphorus | 193 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 76 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 6 ft |
| Surface Area | 131 acres |
| Public Access | Yes |
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).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | 0 m/yr | 2 |
| Phosphorus | ↓ Declining | +113 µg/L/yr | 2 |
Recreation & Access
Location
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.
- ATurtle LakeWalworth County · mi · Two grade letters higher (F → A)
- BDelavan LakeWalworth County · mi · Two grade letters higher (F → B)
- BDelavan LakeWalworth County · mi · Two grade letters higher (F → B)
- CDelavan LakeWalworth County · mi · Two grade letters higher (F → C)
- CDelavan LakeWalworth County · mi · Two grade letters higher (F → C)
Nearby Lakes in Walworth County
More Wisconsin Lake Rankings
State Parks Near Comus Lake
Other Grade F Lakes in Wisconsin
Hypereutrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 1 station on file (most recent sample 2023).
Fish Species (DNR-rated)
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
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.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.