Fish and Aquatic Life
T15N R22E Sec. 36 NESE
Stream Length = 44.0 miles
The Onion River discussion is segmented into two sections to represent the different stream classifications and biological characteristics of the stream from its headwaters downstream. The Onion River is classified as a Cold Water Fish Community stream, Class II trout stream from the headwaters downstream to the top of the Waldo Dam impoundment. A Warm Water Sport Fish Community classification exists from the Waldo Impoundment downstream to the confluence with the Sheboygan River.
ONION RIVER WARM WATER SEGMENT (RM 0.0-31.9)
The lower Onion River extends from the Waldo Dam downstream to its confluence with the Sheboygan River at Rochester Park. It does not completely achieve its potential to support a warm water sport fish community because of water quality and habitat limitations. The reach flows through vast acreage of farmland, where intensive pasturing contributes to erosion and sedimentation. Even light rains, or during periods when the carp are active, the stream becomes turbid, resulting in heavy siltation, and increased nutrient levels due principally to agricultural pollutants (pers. comm. Galarneau). The lower Onion River supports a tolerant warm water fishery with carp, bullhead, northern pike, and green sunfish present.
Overall the Onion River water quality has changed little from the information presented in the Onion River Priority Watershed Plan (WDNR 1981) as compared to our monitoring in 1994. Water quality is still good to excellent in the rivers upstream reaches (above Waldo) and poor in the river’s lower reaches. The rivers tributary streams, specifically Belgium Creek and Lima tributary, are severely degraded due to both point and nonpoint sources and ultimately effect the water quality in the Onion River.
The Onion River Priority Watershed Plan (WDNR 1981) reported that both the biotic index samples and the water chemistry samples above the Hingham impoundment were indicative of good to excellent water quality. While samples collected at the downstream end of the watershed (Ourtown Road) rated the river's water quality as poor. Similar results were observed from our 1994 Onion River water quality monitoring (WDNR 1999).
WDNR personnel surveyed the Onion River approximately 1.6 miles downstream of Ourtown Road in July 2000 (River mile 2.8). The stream reach that was surveyed was within the boundaries of the Pinehurst (“The Bull”) Golf Course. The fish community rated good and included the following species: sand shiner, common shiner, white sucker, greater redhorse, longnose dace, hornyhead chub, smallmouth bass, bluntnose minnow, rock bass, common carp, green sunfish, bigmouth shiner, johnny darter, northern pike, stonecat, blackside darter, black bullhead, black crappie, and bluegill. Stream habitat consisted of a good variety of bottom substrates and habitat types. There were numerous riffle, pool and run areas within the sample reach. However, fish cover was fairly limited. Vegetated buffer areas were good within the stream reach, but heavy agricultural land use within the watershed does contribute a large portion of the sediment and nutrient loading to the Onion River. Future monitoring will be done to determine if the new golf course will have an impact on the stream ecosystem.
ONION RIVER COLD WATER SEGMENT (RM 31.9-44.0)
This segment of the Onion River extends form the headwaters downstream to the top of the pool formed by the Waldo Dam. The potential fishery is currently limited by increased water temperature due to the impoundment and presence of private fish ponds on major spring sources, and siltation from agricultural runoff. This segment is classified as a cold water fish community, Class II trout stream but has the potential of being a Class I stream. The headwaters, Ben Nutt Creek maintains a good diversity of intolerant fish species with tolerant and very tolerant fish species present. Intolerant species include brook and brown trout. Tolerant and very tolerant species include green sunfish, stonecat, and carp.
The diversity of macroinvertebrates is only moderate and decreases in the downstream reaches of this segment. Tolerant stream bottom insects dominate, but the HBI falls in the range of "excellent" to "fair" water quality. This segment supports the most balanced fish and aquatic life community in the watershed.
WDNR personnel surveyed the Onion River upstream of County Highway U in July 2000. The survey was conducted upstream and downstream of a large dairy farm operation for a total of two sample sites. This was done to collect baseline data for a future stream relocation project that is designed to reduce nonpoint source pollutant loading to the stream and improve the stream ecosystem. Downstream areas did appear to be impacted from the farm runoff when compared to the upstream site.
Downstream of the dairy farm the fish community rated poor. Fish species included white sucker, mottled sculpin, brown trout, creek chub, northern brook lamprey, rainbow trout, brook stickleback, common carp, brook trout, central mudminnow, and golden shiner. Stream habitat was impacted by the dairy farm with inadequate buffer areas along the streambank, sedimentation on the bottom substrate, bank erosion, and lack of fish cover.
Upstream of the dairy farm the fish community rated fair. Fish species included brown trout, mottled sculpin, white sucker, northern brook lamprey, and rainbow trout. Stream habitat had an excellent buffer of woodland, shading was higher, bank erosion was minimal, bottom substrate had more rock and gravel, and fish cover was better, but still limited.
Author Aquatic Biologist
BEN NUTT CREEK T15N R21E Sec. 30
Stream length = 6.0 miles
As the major headwater tributary to the Onion River, this creek drains an area of about nine square miles in the southwest corner of the town of Plymouth. Although classified as a Class II trout stream, brown trout reproduction has been reduced by the presence of dams, ponds, and raceways that cause temperature fluctuations in the headwater springs. Brown trout are planted annually, and the stream experiences heavy fishing pressure. The Hilsenhoff biotic index (HBI) value for the creek was 5.88 indicating "fair" water quality (WDNR 1991). The fishery is composed of brown trout, bluntnose minnow, blacknose dace, creek chub, pearl dace, white sucker, brook stickleback, johnny darter, and mottled sculpin.
Author Surface Water Inventory Of Wisconsin
The Onion River (also known as Ben Nutt Creek) was assessed during the 2018 listing cycle; new biological (macroinvertebrate Index of Biotic Integrity (IBI) scores) sample data were clearly below the 2018 WisCALM listing thresholds for the Fish and Aquatic Life use. This water was meeting this designated use and was not considered impaired.
Author Ashley Beranek
Onion River (51200) from Cth N to its headwaters was assessed during the 2016 listing cycle; total phosphorus and biological (macroinvertebrate and fish Index of Biotic Integrity (IBI) scores) sample data were clearly below 2016 WisCALM listing thresholds for the Fish and Aquatic Life use. This water is meeting this designated use and is not considered impaired.
Author Ashley Beranek
The Onion River (CTH N to confluence with Sheboygan River) was assessed during the 2018 listing cycle; total phosphorus sample data clearly exceeded 2018 WisCALM listing thresholds for the Fish and Aquatic Life use. However, available biological data did not indicate impairment (i.e. no macroinvertebrate or fish Index of Biotic Integrity (IBI) scored in the "poor" condition category)This water is not meeting this designated use and is considered impaired.
Author Amanda Smith
The Onion River (51200), from its mouth to Cth N, was added to the impaired waters list for total phosphorus in 2012. The 2016 assessments showed continued impairment by phosphorus; total phosphorus sample data exceed 2016 WisCALM listing criteria for the Fish and Aquatic Life use and biological impairment was observed (i.e. at least one macroinvertebrate or fish Index of Biotic Integrity (IBI) scored in the poor condition category). Based on the most updated information, no change in existing impaired waters listing is needed.
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 2016 . See also 'monitoring' and 'projects'.
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 and implementation of a Total Maximum Daily Load Analysis, habitat restoration work, partnership education and outreach and more. If specific recommendations exist for this water, they will be displayed below.
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
|WBIC||Official Waterbody Name||Station ID||Station Name||Earliest Fieldwork Date||Latest Fieldwork Date||View Station||View Data|
|51200||Onion River||10015853||Onion River - Upstream Side Winooski Rd. Bridge||9/25/1990||9/25/1990||Map||Data|
|51200||Onion River||10011283||Onion River - Onion River at Bohnhoff Farm||11/14/2000||10/11/2004||Map||Data|
|51200||Onion River||10021117||Unnamed Tributary To Ben Nutt Creek||4/19/2007||4/19/2007||Map||Data|
|51200||Onion River||10030869||Onion River 250m DS of Blueberry Ln||Map||Data|
|51200||Onion River||603315||Onion River - Winooski Rd Bridge Upst||7/31/1990||8/21/1990||Map||Data|
|51200||Onion River||10009410||Ben Nutt Creek Sumac Lane Stocking Site||Map||Data|
|51200||Onion River||10009429||Onion River Cty E Stocking Site||5/11/1994||12/13/1994||Map||Data|
|51200||Onion River||10028735||Onion River At Elderberry Lane||5/20/2008||1/1/2015||Map||Data|
|51200||Onion River||10030550||Onion River ||9/10/2009||11/3/2009||Map||Data|
|51200||Onion River||603340||Onion River at Cth E Or1||3/28/1994||10/25/2017||Map||Data|
|51200||Onion River||603236||Onion River at Cty Hwy U||9/12/1978||10/30/1978||Map||Data|
|51200||Onion River||10009329||Onion River 1 At Blueberry Road||11/7/2002||11/7/2002||Map||Data|
|51200||Onion River||603290||Onion River at Cth Ac||8/31/1978||10/16/1990||Map||Data|
|51200||Onion River||603303||Onion River at Cth U 1m (Bi)||5/17/1979||10/31/1979||Map||Data|
|51200||Onion River||603313||Onion River - 200 M Dwnstrm Mill Cr||7/31/1990||8/21/1990||Map||Data|
|51200||Onion River||10008153||Unnamed Tributary To Onion River||Map||Data|
|51200||Onion River||10010263||Onion River - Ben Nutt Creek 1at Sth 67 (60m Upstream))||5/17/1979||10/2/2003||Map||Data|
|51200||Onion River||10030871||Onion River 250m DS of Hwy E||Map||Data|
|51200||Onion River||10034387||Onion River - at Bonhoff property bridge crossing||Map||Data|
|51200||Onion River||603302||Ben Nutt Creek at Sth 67 (Bi Sur)||9/25/1990||9/25/1990||Map||Data|
|51200||Onion River||10008169||Onion River - Onion River Upstream Of Bohnoff Site 56 M From Farm Bridge||Map||Data|
|51200||Onion River||10034214||Ben Nutt Creek at Sumac Rd.||8/18/2015||11/11/2015||Map||Data|
|51200||Onion River||10047502||Ben Nutt Creek 200m DS Sumac Rd||Map||Data|
|51200||Onion River||603314||Onion River - 500 M Downst Of Mill Cr||7/31/1990||8/21/1990||Map||Data|
|51200||Onion River||10008174||Onion River Bohnoff Site Downstream Of Cattle Bridge||Map||Data|
|51200||Onion River||10008195||Onion River - Un Creek Kamrath Trib To The Onion River 100 M Downstream Of Cthy Zz ||Map||Data|
|51200||Onion River||10030870||Onion River at Hwy E||8/6/2015||8/6/2015||Map||Data|
Onion River is located in the Onion River watershed which is 98.00 mi². Land use in the watershed is primarily agricultural (76%), forest (9%) and a mix of wetland (7%) and other uses (8%). This watershed has 132.85 stream miles, 143.10 lake acres and 5,098.92 wetland acres.
Nonpoint Source Characteristics
This watershed is ranked Not Available for runoff impacts on streams, Not Available 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.