Issues and Actions

What are the Issues?

Water Quality

Green Lake and four of its seven major tributaries are listed as impaired waterways (Hill Creek, Roy Creek, Silver Creek and Wuerches Creek). Learn more about Wisconsin’s impaired waters. Reasons for impairment within the Green Lake watershed include low dissolved oxygen levels and degraded habitat. Contributing pollutants consist of high phosphorous and sediment levels. Search impaired waters within the Big Green Lake Watershed. Dissolved oxygen levels seasonally decline at a depth of about 10 meters within Green Lake, and in 2014, the lake was listed as impaired for low oxygen levels. The lake’s water quality issues are likely linked to nonpoint source pollution.

impaired waters in the green lake watershed map

Impaired waters within Green Lake watershed
Official Name Local Name Year Listed Water Body Identifcation Code Pollutant Impairment Priority
Green Lake Green Lake (Big Green) 2002 146100 PCBs Contaminated Fish Tissue Low
Green Lake Green Lake (Big Green) 2014 146100 Total Phosphorus Low DO High
Hill Creek Hill Creek 2002 146200 Sediment/Total Suspended Solids Degraded Habitat High
Hill Creek Hill Creek 2016 146200 Total Phosphorus Degraded Biological Community High
Roy Creek Roy Creek 2014 148200 Total Phosphorus Impairment Unknown High
Roy Creek Roy Creek 2002 148200 Sediment/Total Suspended Solids Degraded Habitat High
Silver Creek Silver Creek 1998 146800 Sediment/Total Suspended Solids Elevated Water Temperature, Degraded Habitat High
Silver Creek Silver Creek Mouth 2012 146800 E. coli Recreational Restrictions – Pathogens Low
Twin Lakes Big Twin Lake 2014 146500 Total Phosphorus Excess Algal Growth High
Unnamed Unnamed Trib to Silver Creek 2016 146900 Total Phosphorus Degraded Biological Community High
Unnamed Wuerches Creek 2008 148300 Total Phosphorus Low DO, Elevated Water Temperature High
Unnamed Wuerches Creek 1998 148300 Sediment/Total Suspended Solids Degraded Habitat High
Unnamed North Tributary to Silver Creek 2016 147400 Total Phosphorus Impairment Unknown High
Unnamed Unnamed Trib to Silver Creek 2016 147700 Total Phosphorus Impairment Unknown High

Sediment and Phosphorus Loads

Current research on Green Lake’s water quality focuses on quantifying the effects of sediment inputs, phosphorus runoff, dissolved oxygen levels, and other metrics that may contribute to the lake’s impaired status. Point source and non-point source pollution from both urban and agricultural sources may contribute to Green Lake’s water quality impairments. Managers and researchers are conducting studies to more precisely identify the impact of sediment and phosphorus loads in the Green Lake watershed.

Aquatic Invasive Species (AIS)

AIS observed in Green Lake include Eurasian water milfoil, zebra mussels, curly-leaf pondweed, rusty crayfish and German carp. The introduction of these species has disrupted the Green Lake ecosystem.

What is Being Done?

In 2011, the Green Lake planning team began work on the first Lake Management Plan, which was published in January 2013. The Lake Management Plan summarizes the main issues facing Green Lake, presents research and data about the lake’s quality, and lays out strategies for mitigating these challenges. The Lake Management Plan is the framework used by Green Lake’s stakeholders when taking action to improve the quality of the lake.

The Green Lake Planning Team consists of the Green Lake Association, the Green Lake Sanitary District, the Green Lake Conservancy, Green Lake and Fond du Lac County Land and Water Conservation Departments, the cities of Green Lake and Ripon, the United States Geological Survey, and the Wisconsin Department of Natural Resources. See our partners to learn more.

Best Management Practices

Best Management Practices (BMPs) are land use practices and structures that provide favorable conditions for water quality improvement. Examples include “hard” practices, such as the installation of sediment basins, stream bank and shoreline improvements structures; and “soft” practices including no-till farming, cover crops, and terracing to prevent erosion. BMPs are critical to the Green Lake management goal of reducing phosphorus loads into the lake. Nonpoint source pollution, from both agricultural and developed areas, contributes to increased phosphorus and sediment loads reaching the lake. Working with farmers and shoreline property owners to implement BMPs that reduce runoff of phosphorus and sediment into the lake is an important goal within the watershed. Green Lake partners work with residents to educate them about BMPs, to provide funding for implementation of BMPs, and to evaluate the success of BMPs once they are implemented.

The Green Lake Association (GLA), the Green Lake Sanitary District (GLSD), Green Lake and Fond Du Lac County Land and Water Conservation Departments, the National Resource Conservation Service (NRCS), and the nonprofit contractor Golden Sands Resource Conservation and Development are all involved with BMP implementation.

Read more about BMPs in the Green Lake watershed.


Data collection is an important facet of lake management at Green Lake. Keeping records of stream flow, nutrient levels, plant and animal species populations, and other metrics allows lake managers to assess the state of the lake and to make decisions about future management strategies.


Outreach and education are key components of the strategy to improve Green Lake’s water quality.

Because of Green Lake’s tourist industry, it is important that recreational users of the lake are informed about best practices for preventing the spread of aquatic invasive species. The Department of Natural Resources and UW Extension have teamed up to implement the Clean Boats, Clean Waters program.

Resident outreach is another focus in Green Lake, particularly around the implementation of BMPs. In the Green Lake watershed, this includes two primary resident groups: farmers and shoreline residents. The more educated and engaged residents are, the more likely they are to successfully implement BMPs. Ongoing efforts are in place by several watershed partners to create dialogue among farmers and shoreline owners and to educate residents about best practices.

The Green Lake Association provides educational resources for watershed residents, including a video tour focusing on points of interest within the watershed.