Oconto River, Lower Oconto River Watershed (GB03)
Oconto River, Lower Oconto River Watershed (GB03)
Oconto River (440200)
4.22 Miles
9.94 - 14.16
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, Macroinvertebrate, Cool-Cold Headwater, No Classification, COOL-Warm Headwater, Large River
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
Mercury Contaminated Fish Tissue
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.
Fish and Aquatic Life - waters that do not have a specific use designation subcategory assigned but which are considered fishable, swimmable waters.
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.

Historical Description

The Oconto River arises at the confluence of the North Branch and South Branch Oconto
rivers near Suring, flowing south, then east, to Green Bay. It is a hard-water stream,
containing slightly alkaline water. Oconto Falls Pond and the Machickanee Flowage are
impoundments on the river. Information on both impoundments is contained in the
Lakes Report.
Fish inhabiting the river include northern pike, walleye, largemouth bass, smallmouth
bass, panfish, carp and trout. Brook, brown and rainbow trout are present in the upper
portions of the river where it is classified as a Class III trout stream. Seasonal runs of
Great Lakes trout and salmon occur at the mouth.
The Army Corps of Engineers maintains a federal navigation channel at the mouth of the
Oconto River. The harbor and navigation channel were last dredged in 1974. The Corps
found elevated levels of oil and grease in some sediment samples taken from the
navigation channel in the late-1980s.
The lower Oconto River was one of the most seriously degraded rivers in the state in the
mid- 1970s. In 1975, the river was the largest single source of ammonia nitrogen on the
Wisconsin side of Lake Michigan. The source of pollution was the Scott Paper Company
pulp and paper mill in Oconto Falls. The state of Wisconsin and the U.S. Environmental
Protection Agency initiated enforcement action against Scott in 1977.
Scott Paper Company ceased its pulping operations at Oconto Falls in 1978. In January,
1979, enforcement actions against Scott were settled by stipulation before trial with
Scott paying a $1 million settlement. DNR was allocated $600,000 to develop and
implement a restoration and management plan for the lower Oconto River including the
Machickanee Flowage. Results were to include improvements to fish and wildlife
habitats, aquatic environments, water quality and recreational opportunities.
Background studies conducted in 1979 and 1980 determined existing conditions and
assessed management alternatives. Extensive public involvement efforts were made and
public input into the planning process was solicited. The field investigations showed
water quality below Oconto Falls had improved dramatically since 1978. The fishery in
the river below the Machickanee Flowage had catchable numbers of smallmouth bass,
walleye, northern pike, panfish, trout and salmon. However, the fishery in the
Machickanee Flowage and the river above the flowage consisted of more than 90 percent
rough fish (carp, bullheads and suckers). The approximately two million cubic yards of
soft sediment in the flowage was the apparent limiting factor in establishing a viable
sport fishery as this sediment was an unsuitable substrate for fish spawning,
macroinvertebrates and rooted aquatic plants.

Date  1993

Author   Surface Water Inventory Of Wisconsin

Historical Description

A plan for the restoration of the Oconto River was completed in October, 1980. The
plan recommended continued water quality and fisheries management, drawdown of the
Machickanee Flowage to allow the sediments to dry and compact, chemical treatment for
rough fish removal from the flowage, stocking of various sport fish species, development
of public access sites, and habitat improvements.
Plan implementation began in May, 198 1, with drawdown of the Machickanee Flowage to
the sill of the Stiles dam, almost down to the old river channel. As the sediment
dewatered and dried, considerable compaction occurred. The sediment volume was
reduced by 26 to 49 percent depending on site location and particle size. As sediment
dried, terrestrial vegetation quickly sprouted in the cracks. Most areas of the sediment
were covered by a thick growth of vegetation by the end of the summer.
In September, 1981 the Scott Flowage in Oconto Falls was drawn down for one day to
allow mechanical removal of rough fish between the Scott dam and the Wisconsin
Electric Power Company dam one half mile upstream. Two days after mechanical
removal chemical treatment was used to rid the system of remaining rough fish. More
than 47,000 pounds of fish were removed from the flowage, which was then slowly
refilled. Restocking of more desirable sport fish species began in the fall of 1981 and
continued through 1983.
A number of capital improvements to local facilities have enhanced the Oconto River
area. A grant of $50,000 from the Scott Paper Company settlement money was given to
the city of Oconto Falls to design and construct a new wastewater treatment plant. A
county-owned fishing access area, including boat ramp and dock, parking area.
restrooms, and accessible pier was constructed at a cost of $3 1,000. Two additional
county-owned and two city-owned access areas were also developed.
The Oconto Electric Cooperative (OEC) operates the Stiles dam, which creates the
Machickanee Flowage. as a "peaking" facility, generating at full capacity at "peak" demand
periods and cutting back generation during "off-peak" hours. This mode of operation
results in rapid, large fluctuations in flow from less then 200 cubic feet per second (cfs)
to 1,000 cfs in 20 to 30 minutes, and prolonged periods of reduced flow, sometimes less
than 125 cfs. After a large fishkill in July, 1983, that coincided with a period of low
flows, the DNR initiated a petition to the Federal Energy Regulatory Commission (FERC)
requesting an increase in minimum flows.

Date  1993

Author   Surface Water Inventory Of Wisconsin

Historical Description

After numerous attempts at negotiating an increase in flow, the DNR and the US. Fish
and Wildlife Service conducted an In-stream Flow Incremental Methodology (IFIM) study
to determine the effects of the dam operation on the quantity and quality of aquatic
habitat in the lower river. The IFIM study results indicated the Stiles dam should be
operated with the following monthly minimum flows in order to protect habitat for
smallmouth bass. rainbow trout and invertebrates:
Month cfs
October 455
November 569
December 486
January 354
February 345
March 558
April 1,242
May 892
June 705
July 410
August 384
September 468

The study further recommended that these flows (or, if lower, the natural flow of the
river above the Stiles dam) be adopted as the minimum constant releases from the Stiles
In September, 1987, DNR filed an amended petition with FERC requesting monthly
minimum flows of 345 cfs in February to a minimum flow of 1,242 cfs in April, as
reflected in the study, with fluctuations of no more than 1.2 foot on the flowage.
Oconto Electric Cooperative, in opposition to the petition, submitted a statement on the
"Impact of Increased Minimum Flow Releases on Revenue Generated by the Oconto
Electric Cooperative Stiles Hydroplant." The U.S. Department of Interior filed a motion
to intervene which reiterated and supported the position expressed by DNR. Oconto
Electric Cooperative also filed a motion to intervene. Additionally, FERC received
comments from several citizens, the Department of Interior's Office of Environmental
Project Review and the National Rural Electric Cooperative Association. In January.
1990, at the request of FERC staff, Oconto Electric Cooperative filed an "Assessment of
Alternative Minimum Flow Regimes on Project Revenues."

Date  1993

Author   Surface Water Inventory Of Wisconsin

Historical Description

The staff at FERC reviewed DNR's petition and materials supplied by Oconto Electric
Cooperative. FERC weighed the benefits to the fishery associated with the proposed flow
regime against those provided by DNR and the U.S. Fish & Wildlife Service, as well as
the costs to the project. FERC's final order amending Oconto Electric's license required
the following flows:
Month cfs
November 1 - February 28/29 200
March 1 - April 30 317
May 1 -June 30 572
July 1 - July 31 410
August 1 - September 30 370
October 1 - October 3 1 317
FERC further ordered that the level in the reservoir be maintained at 108.8 to 110 feet.
Studies and modeling of the assimilative capacity of the Oconto River between Oconto
Falls and Oconto were conducted in 1989 (Fenske, 1989). Major influences on dissolved
oxygen included re-aeration, photosynthesis, and river flow. The studies concluded that
wastewater discharges from Scott Paper Company and the village of Oconto Falls do not
significantly impact dissolved oxygen levels and that wasteload allocations are not
necessary to protect water quality in this segment of the river.
Aquatic plants (milfoil) are abundant from Stiles downstream. The Bureau of Fisheries
Management continues to stock portions of the Oconto River.
The exotic zebra mussel (Dreissena polymorpha) has been found in Green Bay waters.
Concern has arisen that the mussel may alter the ecology of Wisconsin's inland aquatic
systems. Zebra mussels also pose a threat to water intake systems, which become
clogged with the mussels, and have been known to impact recreational activities such as
boating and fishing. The DNR should monitor the spread of this invader.

Date  1993

Author   Surface Water Inventory Of Wisconsin

Oconto River, Lower Oconto River Watershed (GB03) Fish and Aquatic LifeOconto River, Lower Oconto River Watershed (GB03) RecreationOconto River, Lower Oconto River Watershed (GB03) Fish Consumption

Impaired Waters

The 2018 assessments of the Oconto River (miles 31.43-35.81) showed continued impairment by temperature; new temperature sample data exceeded the 2018 WisCALM listing criteria for the Fish and Aquatic Life use. Based on the most updated information, no change in the existing impaired waters listing was needed.

Date  2017

Author  Ashley Beranek

Impaired Waters

Oconto River (440200) in Shawano Co was assessed during the 2016 listing cycle; temperature data exceeded 2016 WisCALM listing thresholds for the Fish and Aquatic Life use.

Date  2015

Author  Aaron Larson


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.



Best Management Practices, Implement
Partnering with property owners, Machickanee Advancement Association is sponsoring a grant to implement water quality and habitat best practices from Wisconsin's Healthy Lakes Implementation Plan. Best practices, including fish sticks, 350 sq. ft. native plantings, diversions, rock infiltration, and/or rain gardens, will be designed and installed according to the Healthy Lakes fact sheets, technical guidance and grant application.
Monitor Fish Tissue
440200 name Oconto River TMDL ID 173 Start Mile 10.41 End Mile 14.63
Monitor Fish Tissue
440200 name Oconto River TMDL ID 173 Start Mile 0 End Mile 9.94

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

Oconto River is located in the Lower Oconto River watershed which is 196.48 miĀ². Land use in the watershed is primarily forest (33.70%), agricultural (25.80%) and a mix of wetland (23.90%) and other uses (16.60%). This watershed has 314.34 stream miles, 3,972.16 lake acres and 24,684.40 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Low 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.

Natural Community

Oconto River is considered a Warm Mainstem, Macroinvertebrate, Cool-Cold Headwater, No Classification, COOL-Warm Headwater, Large River 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.

Cool (Warm-Transition) Headwaters are small, sometimes intermittent streams with cool to warm summer temperatures. Coldwater fishes are uncommon to absent, transitional fishes are abundant to common, and warm water fishes are common to uncommon. Headwater species are abundant to common, mainstem species are common to absent, and river species are absent.

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.

Cool (Cold-Transition) Headwaters are small, usually perennial streams with cold to cool summer temperatures. Coldwater fishes are common to uncommon (<10 per 100 m), transitional fishes are abundant to common, and warm water fishes are uncommon to absent. Headwater species are abundant to common, mainstem species are common to absent, and river species are absent.