Lake Dubay
Marathon County, Wisconsin7,800 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Lake Dubay. Here is what has been measured.
- Eutrophic
- 101 ft max depth
- Public access
Lake Dubay in Marathon County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 64.9 µg/L. Surface area: 7800 acres.
Lake Dubay is a 7,800-acre productive, nutrient-rich eutrophic lake in Marathon County, Wisconsin with an estimated average depth of about 101 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 11 public boat landings. Compared to the 3 other monitored lakes in Marathon County, Lake Dubay ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-15. Methodology: how these readings are compared.
At about 7,800 acres, Lake Dubay is large enough that where you stay decides which shore you see most of. It has 11 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Lake Dubay, and Booking.com and Expedia search hotels near the lake for your dates.
What Lake Dubay is good for
From access and monitoring records, not editorial picks.
- Boat launch11 documented ramps
- Big water7,800 acres
Swimming conditions
Readings onlyElevated nutrients
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Lake Dubay is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Dubay
These are the measurements Wisconsin DNR publishes for Lake Dubay, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.5 ft of visibility. Phosphorus 64.9 µg/L. TSI 64.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 64.9µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 64 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake Dubay
Answers come straight from the public measurements and survey records on this page.
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Lake Dubay covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Lake DuBay comprehensive survey 2022Comprehensive Survey · WI DNR (PDF)
Lake Details
Max depth
~101 ft est.
Surface area
7,800 acres
Public access
Yes
Listed by Wisconsin DNR
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wisconsin has not published bathymetry for Lake Dubay.
Lake Size & Watershed
Watershed (drainage) area
4,951 sq mi
HydroLAKES / HydroSHEDS
Shoreline
46.2 mi
HydroLAKES / HydroSHEDS
Elevation
1,109 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- US 10 and River RoadPublic
- Du Bay ParkPublic
- South DrivePublic
- Highway CPublic
- River RoadPublic
- Chuck's LandingPublic
Showing 6 of 11 documented landings from the USGS National Boat Ramps inventory.
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Lake Dubay
Compare lakeside cabins, hotels, and vacation rentals near Lake Dubay in Marathon County, Wisconsin — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Dubay are listed below.
Top-rated places to stay near Lake Dubay
Prices for Oct 16–18, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Lake Dubay → · more Wisconsin lake trips
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Fishing Lake Dubay
Water Quality Trend: Worsening
Based on 7 years of monitoring (2020–2026).
Water clarity
Stable6 years
Phosphorus
Worsening+5.83 µg/L/yr6 years
Reservoir Info (USACE NID)
Lake Dubay is a man-made reservoir impounded by the Dubay (completed 1942), built primarily for hydroelectric on the Wisconsin River; concrete-type dam, 40 ft tall and 8,630 ft long.
- Surface area
- 7,800 ac
- Normal storage
- 128,000 ac-ft
- Max storage
- 128,800 ac-ft
- Drainage area
- 4,822 sq mi
- Hazard class
- High
- Owner
- Consolidated Water Power Company
All listed purposes: Hydroelectric;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID WI00784 · Operator website
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lake Dubay under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Mullins Cheese IncKnowlton Tn · 1.3 mi away · NPDES WI0054127Recent violation
- Ephraim Wastewater Treatment FacilityEphraim · 3.7 mi away · NPDES WI0061271Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Marathon County
Frequently asked questions about Lake Dubay
Where is Lake Dubay?
- Lake Dubay is a lake in Marathon County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Lake Dubay?
- Lake Dubay in Marathon County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 64.9 µg/L. Surface area: 7800 acres.
Is Lake Dubay safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Lake Dubay?
- No published bathymetric survey covers Lake Dubay, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 101 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 7800 acres.
Are there boat ramps on Lake Dubay?
- Lake Dubay has 11 documented boat landings in the USGS National Boat Ramps inventory. Named access points include US 10 and River Road, Du Bay Park, South Drive, Highway C, among others. Public access is listed as yes.
Can I fish at Lake Dubay?
- Lake Dubay has 11 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Lake Dubay across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Wisconsin
Fish species and best lakes in Marathon County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its readings
Lakes in the Wisconsin River Watershed, ranked by water quality
Wisconsin's cleanest lakes, ranked on agency measurements
More lakes in Wisconsin
State Parks Near Lake Dubay
Other Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Where this data comes from
58 measurements from 2 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX58 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory