Turtle Creek, Turtle Creek Watershed (LR01)
Turtle Creek, Turtle Creek Watershed (LR01)
Turtle Creek (790300)
10.81 Miles
24.77 - 35.58
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 Natural Communities.
Warm Mainstem, COOL-Warm Mainstem
Year Last Monitored
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
This river is impaired
Low DO
Total Phosphorus
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.
Supported Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
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.
Supported Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
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.


Turtle Creek--Comus Lake to Rock-Walworth County Line This 13-mile stretch of stream (plus Comus Lake) is buffered by more than 2,000 acres of adjacent wetlands in the nearby state-owned wildlife area. This segment is, however, affected by urban polluted runoff from the city of Delavan and exhibits low dissolved oxygen and high turbidity, especially during low flow conditions. A marginal smallmouth bass fishery exists and the threatened Ozark minnow has been found in a tributary to this stretch. In the past, WDNR proposals for habitat enhancements have been deferred due to excessive polluted runoff impacts and the stream's natural limitations. This segment's potential is considered warm water forage fishery.

Date  2002

Author   Aquatic Biologist

Historical Description

Turtle Creek is the second largest stream in Rock County and is an important recreational asset. The stream originates in Walworth County, enters Rock County at Fairfield and flows southwest to the Rock River just below Beloit in Illinois. Turtle Creek is managed for smallmouth bass; additional game fish species which occur in varying numbers include walleyes, black crappies, rock bass, northern pike, and channel catfish. The latter two species are concentrated in the lower reaches of the river. Carp are abundant at times, along with redhorse, suckers, and forage species.

Adjoining fresh meadow wetland totals 128 acres and is concentrated in the upper portion of the stream. About 13 percent of the wetland is wooded. Approximately 2 miles of the stream runs through the Turtle Creek Wildlife Area which includes 312 acres of public hunting and fishing grounds in Rock County. Spring flow in both Rock and Walworth Counties maintain open water the year round in the wildlife area, and approximately 2,000 mallards and 2,000 Canada geese over-winter here. The area is also used extensively by feeding and resting waterfowl during migration periods and habitat improvement has greatly increased nesting densities in recent years. The area also has a good natural pheasant population which is supplemented by stocking during hunting season. In addition to hunting and fishing, Turtle Creek is one of the better streams in southern Wisconsin for canoeing. There is also one town park and one city park located on the stream. Access is available at the wildlife area and the parks, and is possible at six town roads, two county roads and one state highway crossing.

Surface Acres = 285.1, Miles = 24.5, Gradient = 4.5 feet per mile.

From: Ball, Joseph R., and Ronald J. Poff, Lake and Stream Classification Project. Surface Water Resources of Rock County, Department of Natural Resources, 1970.

Date  1970

Author   Aquatic Biologist

Turtle Creek, Turtle Creek Watershed (LR01) Fish and Aquatic LifeTurtle Creek, Turtle Creek Watershed (LR01) RecreationTurtle Creek, Turtle Creek Watershed (LR01) Fish Consumption

Impaired Waters

Turtle Creek, from its headwaters to Comus Lake, was evaluated for phosphorus in the 2022 cycle and found to have levels above the statewide criteria. This segment of Turtle Creek was added to the 2022 Impaired Waters List.

Date  2022

Author  Ashley Beranek

Impaired Waters

Turtle Creek (WBIC 790300) from Rock/Walworth county line to Comus Lake in Delavan was listed for total phosphorus in 1998. This segment of Turtle Creek was assessed during the 2018 listing cycle; new biological (fish Index of Biotic Integrity (IBI) scores) sample data were clearly below the 2018 WisCALM listing thresholds for the Fish and Aquatic Life use. Based on the most updated information, no change in the existing impaired waters listing was needed.

Date  2017

Author  Ashley Beranek

Impaired Waters

The 2018 assessments of Turtle Creek (IL, WI state line to Rock/Walworth county line) showed impairment by phosphorus; new total phosphorus sample data exceeded the 2018 WisCALM listing criteria for the Fish and Aquatic Life use. However, new and existing biological data did not indicate impairment (i.e. no macroinvertebrate or fish Index of Biotic Integrity (IBI) scored in the "poor" condition category). This water was also assessed for temperature; new temperature sample data exceeded the 2018 WisCALM listing criteria for the Fish and Aquatic Life use. Based on the most updated information, this water was proposed for the impaired waters list.

Date  2017

Author  Ashley Beranek


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.



Citizen-Based Stream Monitoring
Collect chemical, physical, and/or biological water quality data to assess the current overall stream health. The data can inform management decisions and may be used to identify impaired waters for biennial lists.
Citizen-Based Stream Monitoring
Collect chemical, physical, and/or biological water quality data to assess the current overall stream health. The data can inform management decisions and may be used to identify impaired waters for biennial lists.
Nine Key Element Plan
Turtle Creek PWS Plan - Nine Key Element Plan - The purpose of this project is to develop and document water quality and land use information about the Turtle Creek Watershed so that the specific causes and critical areas contributing to nonpoint source pollution in the watershed can be identified and the most practical means for abating the pollution can be developed.

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

Turtle Creek is located in the Turtle Creek watershed which is 288.47 miĀ². Land use in the watershed is primarily agricultural (69.80%), grassland (9.10%) and a mix of forest (6.50%) and other uses (14.50%). This watershed has 339.80 stream miles, 590.58 lake acres and 6,590.97 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.

Natural Community

Turtle Creek is considered a Warm Mainstem, COOL-Warm Mainstem under the state's Natural Community Determinations.

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

Warm Mainstem waters are moderate-to-large but still wadeable perennial streams with relatively warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon, and warm water fishes are abundant to common. Headwater species are common to absent, mainstem species are abundant to common, and river species are common to absent.