Oconomowoc River, Oconomowoc River Watershed (UR09)
Oconomowoc River, Oconomowoc River Watershed (UR09)
Oconomowoc River (848200)
2.01 Miles
22.90 - 24.91
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
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.
Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
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.


The Oconomowoc River begins in southern Washington County and flows southwesterly to the Rock River in Jefferson County. The river flows through a number of larger natural lakes in Waukesha County. The slender madtom, a small catfish on the state's endangered list, has been found in the Oconomowoc River. The statewide population of this fish has been declining over the past 20 years. The slender madtom is highly sensitive to siltation and water quality problems. Its presence indicates that the reach of the Oconomowoc River where it is found may be some of the best warmwater habitat in southern Wisconsin. This high-quality habitat is threatened by the area's rapid suburbanization (Lyons, 1995).

In 1999, the DNR conducted baseline monitoring on the river. The fisheries data collected indicated that the river was in fair condition. Other data showed the river to be in fair to good condition.

Section above Friess Lake
The Oconomowoc River originates in Section 10 of the Richfield Township, receiving flow at its headwaters from several agricultural drainage ditches. The township is experiencing increasing urbanization.The river flows for five miles before entering Friess Lake. The upper half of the river has been straightened, while the lower portion below Pleasant Hill Road retains much of its natural meander. A major drainage channel enters the river from the north in section 8 of Richfield Township. This section of the Oconomowoc River has many adjacent wetlands important for northern pike spawning.

Date  2002

Author   Aquatic Biologist

Oconomowoc River, Oconomowoc River Watershed (UR09) Fish and Aquatic LifeOconomowoc River, Oconomowoc River Watershed (UR09) RecreationOconomowoc River, Oconomowoc River Watershed (UR09) Fish Consumption


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.



Citizen-Based Stream Monitoring
Collect chemical, physical, and/or biological water quality data to assess the current overall stream health. The data can inform management decisions and may be used to identify impaired waters for biennial lists.
Monitor Water Quality or Sediment
More data collect, continuous monitoring, biology not showing impairment AU: 11485; ID: 10029786
Nutrient Budget Development
North Lake Management District is sponsoring project to complete a sediment and nutrient study for the Oconomowoc River Watershed with the following goals: 1) Estimate watershed sediment, phosphorus, and pollutant sources and loads of the River 2) Evaluate sediment accretion/erosion/transport within the Monches Millpond and the River downstream of the Dam 3) Complete in-stream bank and bed survey 4) Examine sediment and riverbed stability within the former Funks Millpond 5) Communicate results and recommendations to the District, WDNR, and other interested parties. Project deliverables: completion of a comprehensive report including the following elements: 1) Historical, present-day, and planned future land use information to help estimate phosphorus, sediment, and select pollutant loads, 2) Mapped changes to sediment deposits created by using digital orthophotography to evaluate changes to sediment bars and general channel form within the Monches Millpond and the River downstream and related to changes during and immediately after dam reconstruction/removal will also be mapped, 3) On-water survey data including: channel form, sediment types and distribution, debris jams and channel obstructions, eroding banks and unstable channel form, riparian vegetation, and potentially other factors. Attention will be given to channel stability in the former Funks impoundment, millrace, and dam area. 4) Discussion of project background issues, conclusions, and recommendations generated will be in a format useful to the WDNR and average Lake user.
Nine Key Element Plan
Oconomowoc River PWS Plan - Nine Key Element Plan - The Oconomowoc River Priority Watershed Project plan assesses the nonpoint sources of pollution in the Oconomowoc River Watershed and guides the implementation of nonpoint source control measures. These control measures are needed to meet specific water resource objectives for the Oconomowoc River and its tributaries. The purpose of this project is to reduce the amount of pollutants originating from nonpoint sources that reach surface water and groundwater within the Oconomowoc River Priority Watershed Project area.

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

Oconomowoc River is located in the Oconomowoc River watershed which is 130.86 mi². Land use in the watershed is primarily agricultural (24.90%), forest (19.70%) and a mix of wetland (16.90%) and other uses (38.40%). This watershed has 136.99 stream miles, 2,858.66 lake acres and 11,105.19 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.

Natural Community

Oconomowoc River is considered a Warm Mainstem 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.

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