Where is Mercer Lake?

Mercer Lake is a lake in Iron County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.

How deep is Mercer Lake?

Mercer Lake has a maximum depth of 24 feet. The lake covers 181 acres.

Are there boat ramps on Mercer Lake?

Mercer Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mercer Lake. Public access is listed as yes.

Can I fish at Mercer Lake?

Mercer Lake has 1 documented boat landing 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.

Mercer Lake

Iron County, Wisconsin181 acresView map Directions

Wisconsin DNR publishes the water-quality measurements for Mercer Lake. Here is what has been measured.

Clarity

12 ft

Typical for Wisconsin

Secchi · sampled 2026

Phosphorus

15.7 µg/L

Typical for Wisconsin

Measured by Wisconsin DNR

Max depth

24 ft

Bathymetric survey

Area

181 acres

Surface area

Type

Mesotrophic

Trophic class

Trend

Improving

7 years of samples

Mesotrophic
24 ft max depth
Public access

See the measurements Directions Where to stay

Mercer Lake in Iron County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 12 ft visibility. Phosphorus: 15.7 µg/L. Maximum depth: 24 ft. Surface area: 181 acres.

Wisconsin DNR lists Musky as common on Mercer Lake. DNR survey details →

Loading map…

Mercer Lake is a 181-acre mesotrophic lake in Iron County, Wisconsin with a maximum depth of 24 feet. Overall water quality is improving over recent sampling years. The lake supports 7 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 1 public boat landing. Compared to the 15 other monitored lakes in Iron County, Mercer Lake ranks #14 for water quality.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-28. Methodology: how these readings are compared.

Mercer Lake covers about 180 acres in Iron County. It has one public boat landing. Vrbo is where to look for cabins and lake homes around Mercer Lake, and Booking.com and Expedia search hotels near the lake for your dates.

What Mercer Lake is good for

From access and monitoring records, not editorial picks.

Clear water12 ft of visibility
Boat launch1 documented ramp
Fishing7 species recorded

Swimming conditions

Readings only

Low algae

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 Mercer 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.

Compare swimming lakes near Minocqua →

Get alerts for Mercer Lake →

Water quality measurements for Mercer Lake

These are the measurements Wisconsin DNR publishes for Mercer Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Good clarity, visible to about 12 ft. Phosphorus 15.7 µg/L. TSI 43.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	12ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	15.7µg/L	Good 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.	43	Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Moderate nutrients, good water quality

Ask about Mercer Lake

Answers come straight from the public measurements and survey records on this page.

DNR fisheries survey

Wisconsin DNR lists Musky as common on Mercer Lake.

A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mercer 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 2001. 5 stations on file (most recent sample 2025).

Fish Species (DNR-rated)

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

Contour map (PDF) →Full WI DNR LakePage →Water quality stations →

Lake Details

Max depth

24 ft

Surface area

181 acres

Public access

Yes

Listed by Wisconsin DNR

Lake Size & Watershed

Watershed (drainage) area

107 sq mi

HydroLAKES / HydroSHEDS

Shoreline

3.8 mi

HydroLAKES / HydroSHEDS

Elevation

1,585 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).

Recreation & Access

Boat Landings

Yes

Public Access

Mercer LakePublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Mercer Lake

Compare lakeside cabins, hotels, and vacation rentals near Mercer Lake in Iron 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.

Top-rated places to stay near Mercer 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 →

Follow Mercer Lake’s readings

Email me when new measurements post for this lake. Updates stay free.

Or email

Fish Species

Musky Panfish Largemouth Bass Smallmouth Bass Northern Pike Walleye Sturgeon

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

Fishing Mercer 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.

Banded Mystery Snail

Water Quality Trend: Improving

Based on 7 years of monitoring (2020–2026).

Water clarity
Stable
6 years
Phosphorus
Improving
-1.12 µg/L/yr7 years

See year-by-year chart →

Regulated Pollution Sources Nearby

1 EPA-permitted facility operate within about 5 miles of Mercer Lake under Clean Water Act (NPDES) discharge permits.

Mercer Sanitary District No 1
Mercer · 1 mi away · NPDES WI0029602

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 Iron County

San Domingo Lake—View →Grand Portage Lake11.7 ft clear · Mesotrophic—View →Echo Lake—View →Echo Lake6 ft clear · Mesotrophic—View →Martha Lake9 ft clear—View →Lake Tahoe—View →

Frequently asked questions about Mercer Lake

Where is Mercer Lake?: Mercer Lake is a lake in Iron County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Mercer Lake?: Mercer Lake in Iron County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 12 ft visibility. Phosphorus: 15.7 µg/L. Maximum depth: 24 ft. Surface area: 181 acres.
Is Mercer Lake safe to swim in?: Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Mercer Lake?: Mercer Lake has a maximum depth of 24 feet. The lake covers 181 acres.
What fish are in Mercer Lake?: Fish species found in Mercer Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye, Sturgeon. Mercer Lake is located in Iron County, Wisconsin.
What did the DNR fisheries survey find at Mercer Lake?: Wisconsin DNR lists Musky as common on Mercer Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mercer 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 Mercer Lake?: Mercer Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mercer Lake. Public access is listed as yes.
Can I fish at Mercer Lake?: Mercer Lake has 1 documented boat landing 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 Mercer Lake across LakeQuality

Wisconsin Fishing Guide

Fish species and the cleanest lakes across Wisconsin

Iron County Fishing

Fish species and best lakes in Iron County

Lake Fishing Forecast

Species activity outlook by water temperature and season

Northwoods Wisconsin

Top lakes and where to stay in the Northwoods Wisconsin area

Wisconsin Lake Trips

Where to stay at Wisconsin's top lakes, each with its readings

Lake Superior Basin (MN+WI)

Lakes in the Lake Superior Basin (MN+WI), ranked by water quality

The State of Wisconsin's Lakes

Wisconsin's cleanest lakes, ranked on agency measurements

More lakes in Wisconsin

Clearest lakes in Wisconsin

Ranked by Secchi water clarity

All Wisconsin lakes

Every Wisconsin lake with its Wisconsin DNR measurements

Lake water quality by country

Official ratings and named-lake measurements

Other Lakes in Wisconsin

Vilas County · 6 ft

Vilas County · 8 ft

Vilas County · 8 ft

Vilas County · 8.5 ft

Lower Sugarbush Lake

Vilas County · 14 ft

Cochran Lake

Price County · 11.5 ft

Mesotrophic Lakes in Wisconsin

Circle Lily Lake Benson Lake Statehouse Lake South Turtle Lake

Where this data comes from

29 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

Wisconsin Department of Natural ResourcesWIDNR_WQX29 samples · 2020–2026

Analytical methods

Phosphorus by Colorimetry

Monitoring station identifiers (1)

WIDNR_WQX-263126

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.