Ahnapee River, Ahnapee River Watershed (TK04)
Ahnapee River, Ahnapee River Watershed (TK04)
Ahnapee River (94800)
7.86 Miles
0 - 7.86
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.
Warm Mainstem, Warm Headwater
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.
This river is impaired
Degraded Biological Community, PCBs Contaminated Fish Tissue
Total Phosphorus, Unknown Pollutant, PCBs
Door, Kewaunee
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.
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.
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.
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.


The Ahnapee River is a low gradient stream with a 65-acre impoundment at Forestville. It flows through predominantly agricultural land and wetlands in its 117-square-mile watershed. The Ahnapee River generally has good water quality and supports a healthy warmwater fishery. Fish runs occur as far upstream as the dam at Forestville. A fish refuge has been designated from the Forestville dam to 500 feet downstream. It is illegal to take, disturb, catch, capture, kill, or fish for fish in any manner from March 1 to May 15 each year (NR 26, Wis. Adm. Code). Periodic shifts in flow due to Lake Michigan seiche effects are common in this lower reach. Macroinvertebrates collected during a wastewater treatment plant post-operations study in 1983 indicated fair water quality in this reach (Russo, 1983a).
The harbor at the river's mouth has been periodically dredged for navigation. Sediment samples taken by the Army Corps of Engineers in 1986 indicated no sedimentary pollution. However, lead and chemical oxygen demand levels were indicative of moderately polluted sediments (IJC, 1991).
Much of the Ahnapee River's headwater flow comes from a spring pond. This provides suitable habitat for a naturally reproducing, self-sustaining population of brook trout in the first mile of stream. This reach has not yet been classified as a trout stream. One quarter mile of a small tributary called Silver Creek is classified as Class I trout water. (Note: there are two Silver Creeks in the Ahnapee River watershed.)
Fish flesh screening for toxic chemical contamination at the river mouth in 1979 found PCB concentrations exceeding FDA health standards in carp and brown bullheads. It is not known whether these fish became contaminated through exposure in the river or somewhere else in Lake Michigan. There is no current fish consumption advisory for the Ahnapee River. Complete consumption advisories are provided in the Health Guide for People who eat Sport Fish from Wisconsin Waters. Anglers should examine the guide regularly to be aware of possible changes in advisory status.
The wastewater treatment plants for the village of Forestville and the city of Algoma both discharge to the Ahnapee River. The Forestville wastewater treatment plant was upgraded in 1981 and water quality has improved for at least a mile below the outfall (Russo, 1983). However, the plant significantly exceeded suspended solids effluent limits throughout 1991 and 1992. This may be due to its acceptance of concentrated septic effluent and to high levels of infiltration and inflow in the collection system. Water quality in the
Ahnapee River has not been seriously affected. While the Algoma plant is currently operating at or above design hydraulic capacity, it is consistently providing adequate treatment. Discharge limits for the facility were calculated based on a warmwater sportfish classification. However, WDNR staff have recommended that the lower stretches of the Ahnapee River be classified as a great lakes/cold water community (Kincaid, et al., 1990). No industries discharge directly to the surface waters of the Ahnapee River.
Upstream from the dam at Forestville, nonpoint sources of water pollution are a moderate problem. Sediment deposition and nutrient enrichment from agricultural land erosion occur in this reach. Downstream from the
dam, the stream is well-buffered along its banks and nonpoint source problems are minimal. However, there are several intermittent streams that drain significant areas of agricultural land and may contribute to nonpoint
source problems.

From: Willman, Guy and Mike Toneys. 2001. The State of the Lakeshore Basin. Wisconsin Department of Natural Resources, Madison, WI.

Date  2001

Author  Michael Toneys

Ahnapee River, Ahnapee River Watershed (TK04) Fish and Aquatic LifeAhnapee River, Ahnapee River Watershed (TK04) RecreationAhnapee River, Ahnapee River Watershed (TK04) Fish Consumption

General Condition

Notification of Grant Awards in 9 Northeastern Wisconsin counties

The WDNR processed grant applications totalling $1,567,000 for northeastern Wisconsin communities under the Federal Land and Water Conservation Program, Federal Recreation Trails Program and Stewardship Local Assistance Program. As funds are available, grants to communities for public outdoor recreation projects are announced. The following grant projects in the northeastern Wisconsin are being considered for funding:

Brown County Village of Howard ($456,250 and $66,500) to purchase lands for a new park in Glen Kent Estates Subdivision in the western area of the Village of Howard and also for the purchase of 20.4 acres of new park lands within the Hidden Creek Subdivision along Duck Creek in the southeastern area of the village. City of Green Bay ($94,000) to purchase approximately fifteen acres adjacent to Baird Creek Parkway for open green space and waterway protection.

1) Calumet County Calumet County ($300,000) for the development of the Fox River Trail on the abandoned East Central Wisconsin rail corridor from the Brown County line south five miles to just north of Hilbert.

2) Door County City of Sturgeon Bay ($4,500) for additional developments to Cherry Blossom Park.

3) Fond du Lac County City of Waupun ($11,000) for the development of a pedestrian bridge and shelter/restroom building at Harris Mill Park. Fond du Lac County ($86,250) for construction of the Peebles Trail from Highway 151 to St. Peter in the Highway 149 right of way.

4) Kewaunee County Kewaunee County ($177,490) for maintenance and development of segments of the Ahnapee State Trail between Kewaunee and Luxemburg, and for development of Blahnik Park between the Ahnapee State Trail and the Ahnapee River northeast of the city of Algoma.

5) Manitowoc County Village of Reedsville ($5,000) to rehabilitate the entrance of the Mud Creek Nature Trail. Marinette County City of Niagara ($37,500) for renovation of the River Street Parkway to include shoreline preservation and park improvements (trail, parking, fishing platform).

6) Shawano County Town of Belle Plaine ($418,000) for the purchase of the 25.63 acre parcel known as Gibson Island, located on the Cloverleaf Lakes. Winnebago County Town of Winneconne ($4,500) for completion of the Wolf Wilderness Recreation Trail.

Date  2005

Author   Aquatic Biologist

Impaired Waters

The Ahnapee River, from its mouth to Forestville Dam (miles 0 to 7.86) was put on the impaired waters list in 1998 for PCBs in fish tissue. This portion of the river was listed for phosphorus from 2014 to 2022 and is listed for degraded biology.

The Ahnapee River, from Forestville Dam to the headwaters (miles 7.86 to 14.71) was listed in the 1998 cycle for PCBs in fish tissue. Evaluations of phosphorus, temperature, chloride, fish sample data, and bug sample data every two-year cycle from 2018 and 2022 confirmed good condition of Aquatic Life use.

Date  2022

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.



TMDL Development
Volunteer monitoring of TP and TSS on the Ahnapee River.
Partnership Project
The Lakeshore Natural Resources Partnership, Inc. proposes to carry out the goals of its strategic plan by obtaining technical assistance in establishing and implementing a business plan and obtaining equipment necessary for successful communication.
Partnership Project
The Lakeshore Natural Resources Partnership, Inc. proposes to carry out the goals of its strategic plan by obtaining technical assistance in establishing and implementing an endowment program and fund raising plan.
Monitor Water Quality or Sediment
Recommend not listing for temperature based on no exceedances in 2017. Recommend more monitoring.
Monitor Baseline Survey
Basin staff should conduct basin assessment monitoring on streams in the Ahnapee River watershed (TK04) so the watershed can be reevaluated for nonpoint source priorities. Assessment monitoring should include stream habitat surveys (Simonson et al., 1993) to help identify stream segments that are degraded because of the lack of adequate buffers and vegetative filter strips. This information will help guide CREP, the Targeted Runoff Managament (TRM) Program, and other conservation funding programs to the areas of greatest need.

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

Ahnapee River is located in the Ahnapee River watershed which is 135.58 miĀ². Land use in the watershed is primarily agricultural (49.80%), wetland (19.80%) and a mix of grassland (19.50%) and other uses (10.80%). This watershed has 189.28 stream miles, 5,768.81 lake acres and 15,037.67 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked High for runoff impacts on streams, Not Ranked for runoff impacts on lakes and High for runoff impacts on groundwater and therefore has an overall rank of High. 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.


This watershed is 50.00% impervious.

Natural Community

Ahnapee River is considered a Warm Mainstem, Warm Headwater under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model results and 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.

Warm Mainstem waters are moderate-to-large but still wadeable perennial streams with relatively warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon, and warm water fishes are abundant to common. Headwater species are common to absent, mainstem species are abundant to common, and river species are common to absent.

Warm Headwaters are small, usually intermittent streams with warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon, and warm water fishes are abundant to common. Headwater species are abundant to common, mainstem species are common to absent, and river species are absent.

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