Mercer Lake, Flambeau Flowage Watershed (UC14)
Mercer Lake, Flambeau Flowage Watershed (UC14)
Mercer Lake (2313600)
180.90 Acres
Natural Community
Natural communities (stream and lake natural communities) represent model results that use predicted flow and temperature based on landscape features and related assumptions. Ranges of flow and temperature associated with specific aquatic life communities (fish, macroinvertebrates) help biologists identify appropriate resource management goals. Wisconsin Natural Communities.
Shallow Lowland
Year Last Monitored
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
Trout Water 
Trout Waters are represented by Class I, Class II or Class III waters. These classes have specific ecological characteristics and management actions associated with them. For more information regarding Trout Classifications, see the Fisheries Trout Class Webpages.
Outstanding or Exceptional 
Wisconsin has designated many of the state's highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an 'antidegradation' policy that is designed to prevent any lowering of water quality - especially in those waters having significant ecological or cultural value.
Impaired Water 
A water is polluted or 'impaired' if it does not support full use by humans, wildlife, fish and other aquatic life and it is shown that one or more of the pollutant criteria are not met.

Fish and Aquatic Life

Current Use
The use the water currently supports. This is not a designation or classification; it is based on the current condition of the water. Information in this column is not designed for, and should not be used for, regulatory purposes.
Shallow Lowland
Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
Attainable Use
The use that the investigator believes the water could achieve through managing "controllable" sources. Beaver dams, hydroelectric dams, low gradient streams, and naturally occurring low flows are generally not considered controllable. The attainable use may be the same as the current use or it may be higher.
Streams capable of supporting a warm waterdependent sport fishery. Representative aquatic life communities associated with these waters generally require cool or warm temperatures and concentrations of dissolved oxygen that do not drop below 5 mg/L.
Designated Use
This is the water classification legally recognized by NR102 and NR104, Wis. Adm. Code. The classification determines water quality criteria and effluent limits. Waters obtain designated uses through classification procedures.
Default FAL
Fish and Aquatic Life - Default Waters do not have a specific use designation subcategory but are considered fishable, swimmable waters.


Mercer Lake is a medium hard water drainage lake having slightly alkaline, light brown water of moderate transparency. There are two inlet streams, one from Tahoe lake which affords little or no boating use and the other from Grand Portage Lake which is navigable to small craft except for an obstruction beneath the road bridge. The outlet stream, Little Turtle River, is in fact navigable to small craft and is tributary to the Flambeau Flowage. Sand is the predominant littoral material (50 percent) with rubble (25 percent), muck (20 percent) and a few boulders. The shoreline is predominantly upland (85 percent) with the balance being wetland of the bog-coniferous type. Muskellunge, northern pike, walleye, largemouth bass, smallmouth bass, lake sturgeon, perch, bluegill, black crappie, rock bass, pumpkinseed, black bullhead, white sucker, and redhorse inhabit this lake. Lesser scaup, bluewinged teal, hooded merganser, and wood duck utilize this lake on their spring and fall migrations. It is probable that the lake is also utilized by nesting waterfowl. Emergent and submergent vegetation is moderate to dense and the lake is considered to have an aquatic weed problem. There are 65 dwellings, 6 resorts and a church located on the shoreline. Public access with parking is available as well as that of the navigable water type. Iron County has some acreage on the north shore having 0.48 mile of frontage. Sewage effluent from the Village of Mercer is released into this lake near its outlet. Although this is treated effluent, increased nutrient levels can be anticipated in the discharge area. This probability may enhance the development of aquatic plants to even greater problem proportions.

Surface Acres = 183.6, S.D.F. = 2.20, Maximum Depth = 24 feet

Source:1970, Surface Water Resources of Iron County,WI:WI-DNR Mercer Lake, T43N, R3E, Section 36

Date  1970

Author   Aquatic Biologist

Mercer Lake, Flambeau Flowage Watershed (UC14) Fish and Aquatic LifeMercer Lake, Flambeau Flowage Watershed (UC14) RecreationMercer Lake, Flambeau Flowage Watershed (UC14) Fish Consumption

General Condition

Mercer Lake (2313600) was assessed during the 2016 listing cycle; total phosphorus and chlorophyll sample data were clearly below 2016 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use. This water is meeting these designated uses and is not considered impaired.

Date  2015

Author  Ashley Beranek


Wisconsin has over 84,000 miles of streams, 15,000 lakes and milllions of acres of wetlands. Assessing the condition of this vast amount of water is challenging. The state's water monitoring program uses a media-based, cross-program approach to analyze water condition. An updated monitoring strategy (2015-2020) is now available. Compliance with Clean Water Act fishable, swimmable standards are located in the Executive Summary of Water Condition in 2018. See also the 'monitoring and projects' tab.



Lake Management Plan Development
The Mercer Lake Association in cooperation with the Town of Mercer and the US Geological Service (USGS) will conduct a lake/watershed evaluation and develop a final lake/watershed management plan.
Water Quality Planning
Evaluate recommendations from Mercer Lake Management (2014) and identify key recommendations for management.

Management Goals

Wisconsin's Water Quality Standards provide qualitative and quantitative goals for waters that are protective of Fishable, Swimmable conditions [Learn more]. Waters that do not meet water quality standards are considered impaired and restoration actions are planned and carried out until the water is once again fishable and swimmable

Management goals can include creation or implementation of a Total Maximum Daily Load analysis, a Nine Key Element Plan, or other restoration work, education and outreach and more. If specific recommendations exist for this water, they will be displayed below online.


Monitoring the condition of a river, stream, or lake includes gathering physical, chemical, biological, and habitat data. Comprehensive studies often gather all these parameters in great detail, while lighter assessment events will involve sampling physical, chemical and biological data such as macroinvertebrates. Aquatic macroinvertebrates and fish communities integrate watershed or catchment condition, providing great insight into overall ecosystem health. Chemical and habitat parameters tell researchers more about human induced problems including contaminated runoff, point source dischargers, or habitat issues that foster or limit the potential of aquatic communities to thrive in a given area. Wisconsin's Water Monitoring Strategy was recenty updated.

Grants and Management Projects

Monitoring Projects

Watershed Characteristics

Mercer Lake is located in the Flambeau Flowage watershed which is 247.18 miĀ². Land use in the watershed is primarily forest (56.80%), wetland (28.20%) and a mix of open (14.10%) and other uses (0.90%). This watershed has 190.98 stream miles, 10,199.06 lake acres and 43,978.35 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Not Ranked for runoff impacts on streams, Not Ranked for runoff impacts on lakes and Low for runoff impacts on groundwater and therefore has an overall rank of Low. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.However, all waters are affected by diffuse pollutant sources regardless of initial water quality. Applications for specific runoff projects under state or county grant programs may be pursued. For more information, go to surface water program grants.

Natural Community

Mercer Lake is considered a Shallow Lowland under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model resultsand DNR staff valiation processes that confirm or update predicted conditions based on flow and temperature modeling from historic and current landscape features and related variables. Predicated flow and temperatures for waters are associated predicated fish assemblages (communities). Biologists evaluate the model results against current survey data to determine if the modeled results are corect and whether biological indicators show water quaity degradation. This analysis is a core component of the state's resource management framework. Wisconsin's Riverine Natural Communities.

Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.

Maps of Watershed