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Nepco Lake

Wood County, WisconsinMesotrophic

Nepco Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Wood County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. A maximum depth of 29 ft puts Nepco Lake in the middle of Wisconsin's depth distribution. Nepco Lake covers 496 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Nepco Lake ranks 1 of 4 in Wood County, putting it in the upper tier of locally monitored lakes.

Zebra mussel presence at Nepco Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery includes walleye alongside the lake's other 6 documented species — a notable draw for Wisconsin anglers. A documented public access point at Nepco Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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 2025-09-30. Grade methodology: LakeGrade methodology.

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Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Good clarity, visible to about 11 ft. Phosphorus level: 10.9 µg/L. Trophic State Index: 41.

MetricValueGrade
Water Clarity (Secchi Depth)11 ftB
Phosphorus10.9 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)41Mesotrophic

Moderate nutrients, good water quality

Lake Details

CharacteristicValue
Maximum Depth29 ft
Surface Area496 acres
Public AccessYes

Fish Species

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

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

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

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

Invasive & Introduced Species

Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.

Chinese Mystery SnailCurly-Leaf PondweedEurasian Water-MilfoilHybrid Eurasian / Northern Water-MilfoilPurple LoosestrifeRusty CrayfishZebra Mussel

Water Quality Trend: Stable

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

MetricTrendChange/YearYears
Water Clarity Declining-0.775 m/yr4
Phosphorus Improving-1.75 µg/L/yr3
See year-by-year chart →

Recreation & Access

1
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #1 of 4 lakes in Wood County

Nearby Lakes in Wood County

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2013. 1 station on file (most recent sample 2025).

DNR Assessment
Excellent · Reservoir lake
Trophic State Index 42 (mesotrophic) · 5-year average

Fish Species (DNR-rated)

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

Reservoir Info (USACE NID)

Nepco Lake is a man-made reservoir impounded by the Four Mile Creek (completed 1926), built primarily for water supply on the FOURMILE CREEK & BLOODY RUN; gravity-type dam, 33 ft tall and 2,084 ft long.

Surface area
494 ac
Normal storage
4,748 ac-ft
Max storage
6,000 ac-ft
Drainage area
29 sq mi
Hazard class
Low
Owner
Domtar Wisconsin Dam Corp.

All listed purposes: Water Supply;Recreation;Hydroelectric.

Source: USACE National Inventory of Dams, NID ID WI00032 · Operator website

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

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

Most recent sample: 2025-09-30

Monitoring stations: 1

Where to stay near Nepco Lake

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

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