Neshonoc Lake
La Crosse County, WisconsinLimited DataHypereutrophic
Neshonoc Lake grades an F: every scored parameter (clarity) rates poorly, placing it among the most stressed lakes monitored in Wisconsin.
The hypereutrophic status — TSI 91 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. Neshonoc Lake covers 687 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins.
No invasive species are currently listed at Neshonoc Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Neshonoc Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. 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 2022-06-16. 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 0.4 ft of visibility. Trophic State Index: 91.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.4 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 91 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 687 acres |
Location
County Ranking
Ranked #1 of 1 lakes in La Crosse County
Cleaner Lakes Within 30 Miles
Neshonoc Lake holds Grade F. 2 nearby lakes hold higher grades.
Nearby Lakes in La Crosse County
More Wisconsin Lake Rankings
State Parks Near Neshonoc Lake
Other Grade F Lakes in Wisconsin
Hypereutrophic Lakes in Wisconsin
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Neshonoc Lake covering fish populations, stocking, water quality, and management. 1 report on file.
- 2024Lake Neshonoc netting survey, 2024Netting Survey · WI DNR · 2024 (PDF)
Reservoir Info (USACE NID)
Neshonoc Lake is a man-made reservoir impounded by the Neshonoc (completed 1914), built primarily for hydroelectric on the La Crosse River; concrete-type dam, 18 ft tall and 218 ft long.
- Surface area
- 687 ac
- Normal storage
- 3,100 ac-ft
- Max storage
- 3,100 ac-ft
- Drainage area
- 390 sq mi
- Hazard class
- Low
- Owner
- North American Hydro Inc
All listed purposes: Hydroelectric;Recreation.
Source: USACE National Inventory of Dams, NID ID WI00148 · Operator website
EPA Impairment Status
Neshonoc 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 WI10008309 · 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: 2022-06-16
Monitoring stations: 1