Delavan Lake, Turtle Creek Watershed (LR01)
Delavan Lake, Turtle Creek Watershed (LR01)
Delavan Lake (793600)
1906.03 Acres
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.
Deep Lowland
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 lake is impaired
Excess Algal Growth
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.
Deep Lowland
Deep lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
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.
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.


Lake Delavan is a moderately large eutrophic lake in Walworth County. A dam on Swan Creek, the lake's outlet stream, elevates the lake level by three feet. Due to excess nutrients the lake has been plagued for years by poor water quality, severe blue-green algae blooms, excessive populations of rough fish, anoxic conditions and fishkills. Construction of a municipal sewer system eliminated septic systems surrounding the lake by 1981 and a complete restoration was attempted in the late 1980s and 1990s. The restoration included dewatering, pesticide application for carp removal, and extensive alum treatments. However, tons of phosphorus and nutrient-rich sediments remain in the lake.

Although the lake's excess nutrients no longer result in the large blue-green algae mats of the 1970s and 1980s, an overabundant fishery and excessive populations of Eurasian water milfoil are now problematic. An Aquatic Plant Management Plan was completed for the lake in 1993 by Aron & Associates. In 1975, more than 15 percent of the lake's direct drainage was urbanized; today this percentage is likely higher. Plans for a new dog track and numerous new subdivisions in the direct drainage area ensure that stormwater management, construction site erosion, and hydrologic modification will be top concerns for this lake in the coming years.

The Lake Restoration Project implemented by local citizens, governmental units, the University of Wisconsin, WDNR, U.S. Geologic Survey and U.S. Environmental Protection Agency in the 1980s and 1990s included the following milestones: short-circuiting the mixing of nutrients coming into the lake from Jackson Creek; drawing down the lake for treatment of rough fish (carp) with the chemical rotenone; and application of aluminum sulphate on the lake bottom to reduce nutrient exchange between lake sediments and lake water. The plan also included reducing nutrient and sediment loads through wetland restoration and creation. About 125 acres of existing wetland and farmed wetlands at the confluence of Jackson Creek and its major tributary were selected for restoration/creation (Helsel and MacKinnon 1995). An 85-acre wetland was constructed to reduce sediment and nutrients entering the lake. This Lake Renewal Plan, funded by U.S. EPA's Clean Lakes Program, was implemented in coordination with the activities funded under the Turtle Creek Priority Watershed Project.

Rock River Water Quality Management Plan, Lower Rock River Appendix. WT-668-2002. South Central Region, WDNR.

Date  2002

Author   Aquatic Biologist

Historical Description

A large natural lake managed for largemouth bass, pan fish, and walleye. Major management problems are carp and pollution. Rough fish removal has since both state and town roads border the pond. Only one farm has frontage and there are no recreational facilities.

Surface Acres = 2,072, S.D.F. - 2.77, Maximum Depth = 56 feet.Source: 1961, Surface Water Resources of Walworth County,WI: WI-DNR Delavan Lake, T-2-N, R-16-E,

Date  1961

Author   Aquatic Biologist

Delavan Lake, Turtle Creek Watershed (LR01) Fish and Aquatic LifeDelavan Lake, Turtle Creek Watershed (LR01) RecreationDelavan Lake, Turtle Creek Watershed (LR01) Fish Consumption

General Condition

Delavan Lake House In The Wood 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 water was meeting its designated uses and not considered impaired.

Date  2017

Author  Ashley Beranek

Impaired Waters

Delavan Lake (WBIC 793600) was placed on the impaired waters list for total phosphorus and excess algal growth in 2016. The 2018 assessments showed continued excess algal growth; new chlorophyll-a sample data exceeded the 2018 WisCALM listing thresholds for the Recreation use. Total phosphorus data were clearly below the Recreation use and Fish and Aquatic Life use listing thresholds. Based on the most updated information and biologist input, no change in the existing impaired waters listing was needed.

Date  2017

Author  Ashley Beranek

Impaired Waters

Delavan Lake (WBIC 793600) was assessed during the 2016 listing cycle; chlorophyll sample data exceed 2016 WisCALM listing thresholds for the Recreation use, however, total phosphorus data do not exceed REC thresholds. Total phosphorus and chlorophyll data do not exceed Fish and Aquatic Life thresholds.

Date  2015

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 2018. See also the 'monitoring and projects' tab.



Best Management Practices, Implement
Partnering with property owners, Delavan Lake Sanitary District is sponsoring a grant to implement water quality and habitat best practices from Wisconsin's Healthy Lakes Implementation Plan. Best practices, including fish sticks, 350 sq. ft. native plantings, diversions, rock infiltration, and/or rain gardens, will be designed and installed according to the Healthy Lakes fact sheets, technical guidance and grant application.
Best Management Practices, Implement
Partnering with property owners, the applicant is sponsoring a grant to implement water quality and habitat best practices from Wisconsin's Healthy Lakes Implementation Plan. Best practices, including fish sticks, 350 sq. ft. native plantings, diversions, rock infiltration, and/or rain gardens, will be designed and installed according to the Healthy Lakes fact sheets, technical guidance and grant application.
Land Acquisition
1.68 acres of land was acquired along Delavan Lake - Brown's Channel.
Land Acquisition
The Delavan Lake Sanitary District (DLSD) will use this grant to pay for part of the purchase of 18 lots along Browns Channel, part of Delavan Lake, located in the Town of Delavan. The project includes the Brown parcel (1.38 acres) and the Odling Parcel (0.30 acre), zoned Lowland Conservation District (C4). The parcel borders other DLSD lands under protection.
Partnership Project
The Delavan Lake Sanitary District will partner with the Assembly Park subdivision to facilitate the installation of 243,000 square feet of permeable pavers for a 25.4 acre subdivision. Approximately 5 acres of local paved roads will be removed and replaced with permeable pavers.
Habitat Restoration - Shoreland
Walworth County will continue the Walworth County Lakes Specialist position for one year. The Lakes Specialist will provide educational information to lake residents regarding shoreline stabilization and shoreline restoration. The Lakes Specialist will also design shoreline restoration projects for interested landowners, provide technical assistance to contractors and hold workshops on shoreland restoration.
Protect Riparian or Shorelands
Walworth County will implement the Shoreland Protection Initiative project that includes: 1. A baseline lakeshore inventory; 2. ten lakshore demonstration sites; 3. the preparation of lake lawn and yard nutrient management plans; 4. fact sheets on lakeshore stabilization, shoreland buffers, shoreland regulations and lawn care; 5. an annual lakeshore inventory and distribution of shoreland regulation materials; 6. formation of a Walworth Co. Lakes Association and meetings with and newsletter pertaining to Walworth Co. lakes; 7. Workshops, information packets and news articles pertaining to the Fox river Basin Partnership Team Lakes Initiative; and 8. the formation of the Walworth County Land Conservancy.
Restore Wetlands
The Town of Delavan proposes to restore the Mound Road wetland astride the Jackson Creek inflow to Delavan Lake. Project activities include supplemental seeding and planting, control of noxious weeds and undesirable vegetation, and the initiation of long term maintenance and development of public access
County Land and Water Management Plan
The Delavan Lake Sanitary District is sponsoring a project to create a concept plan that will show improvements including a nature trail west of Brown's Channel on the 2.1 acre land that the Sanitary District owns which includes 22 properties. Project final deliverables: 1) Wetland delineation and map; 2) Concept plan created by consultant to show mapped wetland areas and stream bank including erosion and stability issues; 3) Concept plan to include results, management alternatives, cost analysis, and best location for a future nature trail on the West bank of Brown's Channel 4) Baseline assessment of the invasive plant species and location to be created and included in the plan for the properties. Specific project activities: 1) Wetland delineation and mapping; 2) Stream bank location and mapping, including erosion and stability potential of the banks; 3) Assessment of best location for future nature trail; 4) Map invasive plants, species and locations on properties completed by multiple University students and Sanitary District staff; 5) Creation of a public supported updated plan that includes an aquatic invasive species control strategy and a detailed aquatic plant harvesting plan. Special Conditions: 1) Volunteer lists and signatures shall be maintained for reporting in kind volunteer labor.

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

Delavan Lake 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

Delavan Lake is considered a Deep Lowland 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.

Deep lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.