Fish and Aquatic Life
Rock Lake is a borderline high-quality mesotrophic lake. It has been the focus of long-term trend monitoring from 1986 to 1998. In 1999 and 2000, DNR baseline monitoring was conducted on Rock Lake. Ongoing monitoring indicates good water quality, but lake fertility is increasing (WDNR, 1994). This increased fertility may lead to more algae blooms. The lake was chemically treated in the past to control excessive aquatic plant growth, but this management practice has decreased due to potential harm to fish habitat. The lake has a diverse sport fishery supporting both smallmouth and largemouth bass, walleye, northern pike and panfish. A fish consumption advisory exists for walleye; past fish tissue monitoring has found elevated levels of mercury in walleye. The source of the metal is unknown (WDNR, 1994); it may originate from natural sources.
Polluted runoff is the greatest threat to Rock Lake. Residential development along the shoreline and backlot development adjacent to the lake have recently accelerated. Agricultural runoff carrying excess nutrients to the lake also contributes to water quality concerns.
A lake planning grant was awarded to the Rock Lake Improvement Association to develop an overall lake management plan. Other lake planning grants may be needed to address other issues. Rock Lake is monitored through WDNR's self-help monitoring programs. The least darter, a fish on the state's watch list, has been observed in Rock Lake (Fago,1982).
In 1999, the Rock Lake was designated by the DNR Nonpoint Source Pollution Project as a Priority Lakes Nonpoint Source Pollution Control Project. A plan was written and the implementation process in underway. The project will end in 2004.
In 2002, the county acquired 89 acres of wetlands, uplands, and woodlands on the western shore of Rock Lake. The land was purchased for development of a county park.
Also in 2002, Jefferson County obtained a DNR Lakes Planning Grant to conduct a lake classification project in the county. A Citizens Advisory Group was formed of diverse stakeholders in the county to develop a plan to increase protection of the lakes in the county.
Author Aquatic Biologist
Source: 1968, Surface Water Resources of Jefferson County Rock Lake, T7N, R13E, Section 10, 11, 14, 15
A large compound depression in the ground moraine, which has a shoreline greatly altered by the construction in 1865 of a dam with about a 10 foot head. The southern basin of the lake is largely the result of impoundment and is sometimes referred to as Marsh Lake. The fishery consists of northern pike, walleye, yellow perch, largemouth and smallmouth bass and most panfishes. Carp are present but not in problem proportions. The lake is quite fertile and generally clear. There is a 3.1 acre city park and a 15.5 acre county park on its banks. The county park has an improved boat launching site with adequate parking. About 1,700 acres of wetland lie within this watershed and encompass Mud Lake and Bean Lake to the south. The west shore is somewhat marshy and has been the object of some dredging and shore alteration in the past. Large numbers of coots are common; mallards, teal and geese also frequent the lake especially the south lobe (Marsh Lake). The city of Lake Mills borders more than one-third of the shoreline.
Surface Acres = 1,371.0, S.D.F. = 1.43, Maximum Depth = 56 feet
Author Surface Water Inventory Of Wisconsin
Sandy Beach West, Sandy Beach East, Rock Lake Ferry Park Beach, and Bartel's Beach, all of Rock Lake, were assessed for the 2018 listing cycle; E. coli data sample data were clearly below the 2018 WisCALM listing thresholds for the Recreation use. These beaches were meeting this designated use and were not considered impaired.
Author Ashley Beranek
Rock Lake (WBIC 830700) was assessed during the 2018 listing cycle; total phosphorus and chlorophyll-a sample data clearly met the 2018 WisCALM listing thresholds for the Fish and Aquatic Life and Recreation uses. This water was not meeting its designated uses and was considered impaired. No listing change was needed in the existing impaired waters listing.
Author Amanda Smith
Rock Lake (830700) 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 lake is considered impaired for Fish Consumption use and meeting REC and FAL uses.
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|
|830700||Rock Lake||283291||Rock Lake - Ferry Park Beach||6/2/2005||8/30/2017||Map||Data|
|830700||Rock Lake||10003036||Rock Lake||6/1/1990||3/6/2017||Map||Data|
|830700||Rock Lake||10020036||Rock Lake -- Ferry Park Landing Access||6/18/2004||8/24/2017||Map||Data|
|830700||Rock Lake||10003042||Rock Lake - Lake Mil||Map||Data|
Rock Lake is located in the Lower Crawfish River watershed which is 177.65 mi². Land use in the watershed is primarily agricultural (75%), wetland (10%) and a mix of suburban (7%) and other uses (8%). This watershed has 331.66 stream miles, 1,780.53 lake acres and 12,199.86 wetland acres.
Nonpoint Source Characteristics
This watershed is ranked Low 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.