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B

Fawn Lake

Adams County, WisconsinMesotrophic

Fawn Lake comes in at a B on the grading rubric — a respectable showing for a Wisconsin lake of its size and depth. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Mesotrophic conditions dominate at Fawn Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. At 19 acres, Fawn Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Within Adams County's 19 graded lakes, Fawn Lake ranks 10 — below the local median, though not at the bottom.

No invasive species are currently listed at Fawn Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Fawn Lake, which usually reflects a lack of formal fisheries survey work rather than an empty 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 2026-06-15. Grade methodology: LakeGrade methodology.

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Moderate clarity, visible to about 9.5 ft. Phosphorus level: 20.4 µg/L. Trophic State Index: 46.

MetricValueGrade
Water Clarity (Secchi Depth)9.5 ftC
Phosphorus20.4 µg/LB
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)46Mesotrophic

Moderate nutrients, good water quality

Lake Details

CharacteristicValue
Surface Area19 acres
Public AccessYes

Water Quality Trend: Declining

Based on 7 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.286 m/yr7
Phosphorus Stable+0.16 µg/L/yr6
See year-by-year chart →

Recreation & Access

1
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #10 of 19 lakes in Adams County

Cleaner Lakes Within 30 Miles

Fawn Lake holds Grade B. 4 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Adams County

Reservoir Info (USACE NID)

Fawn Lake is a man-made reservoir impounded by the Fawn Lake (completed 1972), built primarily for recreation on the TROUT CREEK; earth-type dam, 19 ft tall and 1,000 ft long.

Surface area
19 ac
Normal storage
90 ac-ft
Max storage
190 ac-ft
Drainage area
2.2 sq mi
Hazard class
High
Owner
Adams County

Source: USACE National Inventory of Dams, NID ID WI00094 · Operator website

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

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

Most recent sample: 2026-06-15

Monitoring stations: 2

Where to stay near Fawn Lake

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