Overview

Okauchee Lake - 1,187 acres and up to 94 feet deep -- is a large, complex basin bordered by terminal moraine and outwash deposits. It was created by a group of ice blocks entrapped in glacial deposits and its present level is maintained above the natural shoreline by a dam on the Oconomowoc River. In addition to its irregular shore, the lake has the frontage of five islands, which occupy nearly 23 acres of the lake basin. The aquatic vegetation in the lake has historically undergone chemical treatment and mechanical harvesting to improve recreational opportunities; the Okauchee Lake Management District has recently relied solely on mechanical harvesters. Pan fish, northern pike and largemouth bass comprise the fishery; with cisco affording some winter angling opportunity. Muskellunge are stocked annually. Hybrid musky stocking was discontinued in 1989 and since then only true muskies have been stocked. Walleyes have been stalked periodically to enhance the native fishery. Public access is provided through a combination of public and privately owned access sites. Adjoining wetlands are limited to the inlet area of the Oconomowoc River, yet fair numbers of waterfowl rest in the weedy bays during fall migration.

The Okauchee Lake Management District completed an aquatic plant management plan and is also addressing issues such as zebra mussels, Eurasian watermilfoil, adequate public access, user conflicts and riparian rights. In 1992, the district received a Wisconsin Lake Management Planning Grant. The grant was used to contract with the U.S. Geological Survey to monitor lake water quality from 1993 through 1995 and to complete an aquatic plant management plan. The district also participated in a research project designed to reduce Eurasian watermilfoil through reestablishing native aquatic vegetation. While the project was unsuccessful, it did show the willingness of the lake management district to participate in WDNR programs.

In 1994, a representative from the University of Wisconsin Sea Grant Institute identified zebra mussel larvae in Okauchee Lake. While followup tests came up clean, the initial finding raises some concern over the lake's ecological balance. The lake management district greatly assisted in educational efforts and provided WDNR and UW Sea Grant with equipment and personnel to assist in surveys. Adult zebras mussels were confirmed summer 2001.

Date  2002

Author   Aquatic Biologist

Historical Description

Source: 1963, Surface Water Resources of Waukesha County Okauchee Lake T8N, R17E, Section 18 Surface Acres = 1, 187, S.D.F. = 3.20, Maximum Depth = 94 feet A large complex basin bordered by terminal moraine and outwash deposits. The lake was, no doubt, created by a group of ice blocks entrapped in glacial deposits; its present level is maintained above the natural shoreline by a dam on the Oconomowoc River. In addition to its irregular shore, the lake has the frontage of five islands which occupy nearly 23 acres of the lake basin. A major use problem is submergent aquatic vegetation and the lake annually receives chemical treatment for its control. Panfish, northern pike, and largemouth bass comprise the fishery; in addition cisco afford some winter angling opportunity. Public access is available, but poorly marked and not considered adequate. Adjoining wetlands are limited to the inlet area of the Oconomowoc River; however, fair numbers of waterfowl rest in the weedy bays during fall migration.

Date  1963

Author   Surface Water Inventory Of Wisconsin

Impaired Waters

Okauchee Lake (850300) was placed on the impaired waters list for total phosphorus in 2014. The 2016 assessments showed continued impairment by phosphorus; total phosphorus sample data exceed 2016 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use, however chlorophyll data do not exceed REC or FAL thresholds. Based on the most updated information, no change in existing impaired waters listing is needed.

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

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

Okauchee 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.