Overview

A soft water, drainage impoundment located on the Wisconsin River that is the fourth largest lake within the state. The water level is controlled by a hydroelectric power dam having a 30-foot head owned by Wisconsin River Power Company. The water has a light brown color, is alkaline, and has a low transparency. Northern pike, walleye, largemouth bass, black crappie, bluegill, pumpkinseed, yellow perch, black bullhead, and brown bullhead are the significant game fish species. Carp, redhorse, buffalo, white sucker, bowfin, and burbot are also present. Partial winterkill and summerkill conditions occasionally occur. Commercial fishing for rough fish and bullhead has been carried on in the past. Industrial pollution is a problem. There is public access from county-owned parks in Adams and Juneau Counties and numerous road ends; there are commercial facilities; there is one organizational camp; and there are over a hundred dwellings on the flowage. Much of the frontage is owned by the Power Company and expanded developments, including a state park, are now under consideration. Muskrat are significant and beaver are present in backwater areas. Several species of puddle ducks use the flowage for nesting and during their spring and fall migrations.

Source: 1969, Surface Water Resources of Juneau County Castle Rock Flowage, T16N, R4E, Section 13 Surface Acres = 13,387, S.D.F. = 6.05, Maximum Depth = 36 feet

Date  1969

Author   Aquatic Biologist

Historical Description

Jim Kreitlow (NOR) documented dissolved oxygen standards violations while sampling the lake in the mid 1990s. Dissolved oxygen concentrations below 5 mg/l were generally found during the early morning hours, probably a result of algae respiration. Values for pH above 9.0 were documented in 1994, 1995, 1996 and 1997 (9 of 107 samples).

The cause of this impairment is likely a result of excessive nutrient loading (phosphorus) from point and nonpoint sources in the watershed. As a result, the flowage is very eutrophic with abundant algae growth.

The Petenwell and Castle Rock Flowages Comprehensive Management Plan was completed in 1996. This report indicates severe algal blooms cause periodic shifts in dissolved oxygen. During photosynthesis, dissolved oxygen values are high (11-12 mg/l) but during respiration, they can drop below 5.0 mg/l (Storet, 1992 was referenced). The report also indicates blue-green algae are the dominant phytoplankton in the Petenwell and Castle Rock Flowages. The report also references sediment sampling has been completed in both flowages, however additional sampling is recommended. Previous sampling found high levels of 2,3,7,8-TCDD and 2,3,7,8-TCDF in the sediments. PCBs and mercury have also been detected at limited sampling sites. Currently, a fish consumption advisory exists on the flowage for PCBs, dioxin and mercury.

Date  2006

Author   Aquatic Biologist

General Condition

Castle Rock Lake Buckhorn State Park Beach was assessed for the 2018 listing cycle; E. coli data sample data were clearly below the 2018 WisCALM listing thresholds for the Recreation use. This beach was meeting this designated use and was not considered impaired.

Date  2017

Author  Ashley Beranek

Impaired Waters

Castle Rock Flowage was recently evaluated during the ten-year period of 2009 through 2018 for results that were reported to the USEPA for the 2020 Clean Water Act condition report. The waterbody is considered impaired, or in poor condition for designated uses which include the quality of fish and aquatic life, recreational use, and public health and welfare (fish consumption and related). Pollutants or problems encountered during sampling (impairments) are determined based on water quality standards outlined in Wisconsin 2020 Consolidated Assessment and Listing Methodology (WisCALM). Assessment results show water conditions that are potentially harmful for Aquatic Life and Recreation uses due to values for total phosphorus that fall into the range expected for an aquatic community in poor health, therefore this water is listed as impaired.

Assessment results during the 2020 listing cycle show total phosphorus levels that indicate impairment to Aquatic Life and Recreation uses, according to 2020 WisCALM standards. Based on the most updated information, in 2020 the impairment was changed from �water use restrictions� to �high phosphorus levels,� which helps clarify the impairment. This lake has been listed as impaired for total phosphorus since 1998.

Date  2019

Author  Ashley Beranek

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

Castle Rock Lake is located in the Little Roche A Cri Creek watershed which is 196.20 mi². Land use in the watershed is primarily forest (55.60%), agricultural (23.20%) and a mix of wetland (9.70%) and other uses (11.50%). This watershed has 108.40 stream miles, 12,554.07 lake acres and 18,156.97 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Medium for runoff impacts on streams, Low 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.