Overview

Oconomowoc Lake is 767 acres and 62 feet deep. It is a multiple basin lake in the terminal moraine. The Oconomowoc River enters and leaves the lake and is impounded by a 2 foot head structure at the outlet. The water is clear and the bottom gravel. Both inlet and outlet are traversable by boat. Public access is located on the Oconomowoc River immediately downstream of the Upper Oconomowoc Lake dam. The fishery consists of largemouth bass, pan fish and northern pike, with Cisco an additional winter contributor to the creel. Walleyes are stocked and Muskellunge have become established from upstream Okauchee Lake. The absence of large adjoining wetlands detracts from waterfowl value, however, ducks can be observed resting in the center of the lake during fall migration.

The Village of Oconomowoc has been very active in managing Oconomowoc Lake. A lake welfare committee makes recommendations to the village board regarding proper management actions. In the last five years, the village has addressed public access, water quality, the use of aquatic herbicides for the control of aquatic vegetation, swimmers itch control, zebra mussels and purple loosestrife control.

In 1990, the village received a Wisconsin Lake Management Planning Grant to monitor the water quality of Oconomowoc Lake. The U.S Geological Survey has been contracted to monitor the lake from 1991 through 1995.

In 1994, zebra mussel veligers were identified in Okauchee Lake, just upstream of Oconomowoc Lake. Adult zebra mussels were found in the fall of 1999.

Date  2002

Author   Aquatic Biologist

Historical Description

Source: 1963, Surface Water Resources of Waukesha County Oconomowoc Lake T7N, R17E,

A multiple basin lake in the terminal moraine. The Oconomowoc River enters and leaves the lake and is impounded by a 2-foot structure at the outlet. The water is clear and the bottom is primarily gravel. Both inlet and outlet have been traversed by boat and provide the only public access to this large lake. The fishery consists of largemouth bass, pan fish, and northern pike, with cisco an additional winter contributor to the creel. The absence of large adjoining wetlands detracts from waterfowl value, however, ducks are observed resting in the center of the lake during fall migration.

Section 2 Surface Acres 767, S.D.F. = 1.80, Maximum Depth = 62 feet

Date  1963

Author   Surface Water Inventory Of Wisconsin

Impaired Waters

Oconomowoc Lake (849600) was placed on the impaired waters list for Mercury in fish tissue in 1998. This water 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 was also assessed for chlorides and sample data were clearly below 2016 WisCALM chronic and acute listing criteria for the Fish and Aquatic Life use. This lake is considered impaired for Fish Consumption use and meeting REC and FAL uses.

Date  2015

Author  Aaron Larson

Condition

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.

Reports

Recommendations

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

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 Lake 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.