Mason Lake
Adams County, Wisconsin882 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Mason Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Curly-Leaf Pondweed
- 9 ft max depth
- Public access
Mason Lake in Adams County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 1.1 ft visibility. Phosphorus: 105 µg/L. Maximum depth: 9 ft. Surface area: 882 acres.
Wisconsin DNR lists Largemouth Bass as common on Mason Lake. DNR survey details →
Mason Lake is a 882-acre highly nutrient-loaded hypereutrophic lake in Adams County, Wisconsin with a maximum depth of 9 feet. Overall water quality is improving over recent sampling years. The lake supports 5 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 3 public boat landings. Compared to the 17 other monitored lakes in Adams County, Mason Lake ranks #17 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-29. Methodology: how these readings are compared.
Mason Lake covers about 880 acres in Adams County. It has 3 public boat landings, so a lakefront rental is not the only way to get a boat on the water. If you are planning to stay, you can search lake houses and cabins around Mason Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Mason Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
- Fishing5 species recorded
Swimming conditions
Readings onlyRecreation use not supported
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. Mason Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Mason Lake 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 Mason Lake
These are the measurements Wisconsin DNR publishes for Mason Lake, 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 1.1 ft of visibility. Phosphorus 105 µg/L. TSI 73.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 105µg/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. | 73 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Mason Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mason Lake typically sits around 76°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in May (about 69°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (69°F) to its warmest (79°F).
Typical surface water temperature by month, from 20 field readings (2024–2026) via the EPA Water Quality Portal. See the full Mason Lake water temperature breakdown →
Wisconsin DNR lists Largemouth Bass as common on Mason Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mason Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1993. 2 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
Max depth
9 ft
Surface area
882 acres
Public access
Yes
Listed by Wisconsin DNR
Lake Size & Watershed
Watershed (drainage) area
27 sq mi
HydroLAKES / HydroSHEDS
Shoreline
7.1 mi
HydroLAKES / HydroSHEDS
Elevation
787 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Mason Lake - NorthPublic
- Mason Lake - SouthPublic
- Mason Lake - EastPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Mason Lake
Compare lakeside cabins, hotels, and vacation rentals near Mason Lake in Adams 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 Mason Lake are listed below.
Top-rated places to stay near Mason Lake
Prices for Oct 9–11, 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 whole trip? See where to stay at Wisconsin’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Mason Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Improving
Based on 7 years of monitoring (2020–2026).
Water clarity
Improving7 years
Phosphorus
Stable+0.07 µg/L/yr7 years
Reservoir Info (USACE NID)
Mason Lake is a man-made reservoir impounded by the Briggsville (completed 1850), built primarily for recreation on the SOUTH BRANCH NEENAH CREEK; gravity-type dam, 14 ft tall and 250 ft long.
- Surface area
- 856 ac
- Normal storage
- 850 ac-ft
- Max storage
- 700 ac-ft
- Drainage area
- 37 sq mi
- Hazard class
- High
- Owner
- Town of Douglas
Source: USACE National Inventory of Dams, NID ID WI00158 · Operator website
EPA Impairment Status
Mason Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI10000764 · Official waterbody report
Nearby Lakes in Adams County
Frequently asked questions about Mason Lake
Where is Mason Lake?
- Mason Lake is a lake in Adams County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Mason Lake?
- Mason Lake in Adams County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 1.1 ft visibility. Phosphorus: 105 µg/L. Maximum depth: 9 ft. Surface area: 882 acres.
Is Mason Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Mason Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Mason Lake?
- Mason Lake typically sits around 76°F at the surface in August, from 20 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Mason Lake?
- Mason Lake has a maximum depth of 9 feet. The lake covers 882 acres.
What fish are in Mason Lake?
- Fish species found in Mason Lake include Musky, Panfish, Largemouth Bass, Northern Pike, Catfish. Mason Lake is located in Adams County, Wisconsin.
What did the DNR fisheries survey find at Mason Lake?
- Wisconsin DNR lists Largemouth Bass as common on Mason Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mason Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Mason Lake?
- Mason Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Mason Lake - North, Mason Lake - South, Mason Lake - East. Public access is listed as yes.
Can I fish at Mason Lake?
- Mason Lake has 3 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 Mason Lake 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 Adams 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
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Where this data comes from
80 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_WQX80 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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory