Castle Rock Lake, Lower Yellow (Juneau Co.) River Watershed (CW02)
Castle Rock Lake, Lower Yellow (Juneau Co.) River Watershed (CW02)
Buckhorn State Park Beach, Castle Rock Lake (1345700)
0.06 Miles
0 - 0
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's Riverine Natural Communities.
Year Last Monitored
This is the most recent date of water monitoring stored in the SWIMS system. 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.
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.
Fish and Aquatic Life - waters that do not have a specific use designation subcategory assigned but which are considered fishable, swimmable waters.
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.


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

Castle Rock Lake, Lower Yellow (Juneau Co.) River Watershed (CW02) Fish and Aquatic LifeCastle Rock Lake, Lower Yellow (Juneau Co.) River Watershed (CW02) RecreationCastle Rock Lake, Lower Yellow (Juneau Co.) River Watershed (CW02) Fish Consumption

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 (WBIC 1345700) was assessed during the 2018 listing cycle; total phosphorus sample data overwhelmingly exceeded the 2018 WisCALM listing thresholds for the Fish and Aquatic Life and Recreation uses. Chlorophyll-a sample data was not available for assessment. This water was not meeting its designated uses and was considered impaired. No listing change was needed to this already impaired water.

Date  2017

Author  Amanda Smith


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'.



Habitat Restoration - Shoreland

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

Castle Rock Lake is located in the Lower Yellow (Juneau Co.) River watershed which is 261.05 miĀ². Land use in the watershed is primarily forest (43.70%), wetland (43.70%) and a mix of open (6.60%) and other uses (6.00%). This watershed has stream miles, lake acres and 65,343.09 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Low for runoff impacts on streams, Low for runoff impacts on lakes and Low for runoff impacts on groundwater and therefore has an overall rank of Low. 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

Buckhorn State Park Beach, Castle Rock Lake is considered a Reservoir under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model resultsand 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.