2020  E. coli Counts

for Geneva Lake Beaches

Click on the Community to see their public beach results.

2020 Boats docked, moored on Geneva Lake  or stored as in-out service on

Geneva Lake WI  by community.  

total 2020 for web page.png

dark blue = City of Lake Geneva

light blue = Linn north shore

green = Williams Bay

white = Fontana

Orange = Linn south shore.



Overview and Update of the Big Foot Creek Watershed Study.

Big Foot Creek is locted on the southeast end of Geneva Lake.  It drains a large wetland that inclules parts parts of Big Foot Beach State Park in its northern wetland.  The creek has discharge degraded water with poor quality for many years.  Low oxygen, high phosphorus are two of the major water quality issues associated with the Creek.  The GLEA has initiated a study to document the degraded water quality, identify the causes and recommend best management practices to improve Big Foot Creek's water quality. 

The initial step (Phase I) began in the spring of 2019 and ended in the fall of 2019 and included collecting water quality data to confirm the the creek's poor water quality. A Phase I final report will be released in the spring of 2020. The over all project goal is to abate the degraded water quality, specifically the high levels of  phosphorus , low levels of oxygen and the reddish floc that is discharged to Geneva Lake. 


A Wisconsin DNR small scale lake planning grant was awarded in the amount of $3,000 to assist with the project’s costs.  High school students from Badger High School assisted with sample collection and did some field/lab analysis (see above parameter tested*).  The data is presently being processed and  interpreted.  A Phase I report will be prepared  

Phase II of the program was started in the spring of 2020.  Applied Ecological Services was hired for resource inventory,  modeling and to develop best management practices to improve water quality.  A final report on phase Phase II is expected towards the end of 2020.

Five year Private Well Testing Program 

Results of Groundwater testing in the Joint Geneva Lake Environmental Agency – Linn Sanitary District Long-Term Well Testing Program.


As a mean of understanding the groundwater quality within the Geneva Lake basin, the Geneva Lake Environmental Agency and the Linn Sanitary District entered into an agreement to monitor thirteen private drinking wells from different locations around the watershed.  The importance of groundwater in the annual Geneva Lake water budget as identified in several studies makes it important to know what is in the groundwater and what it is delivering to Geneva Lake (Figure 1). 

water sources.jpg

The original selection of wells to be involved in the sampling program was based upon several criteria.

  • Parameters tested for bacteria, nitrates,

  • Past testing results and participants (who wants to be involved?)

  • Aquifer

  • Location: density of homes and soils

  • Distribution within the watershed.

    • North and south shore,

    • Areas where our POWTS testing indicated a concentration of failing/old systems

    • Areas of high density of POWTS

    • Shallow groundwater, w/POWTS

    • Area where past well testing indicated bacterial contamination. 

    • Nearby land use.

Land use and the use of private on-site wastewater treatment systems in the Town of Linn are potential threats to groundwater quality.  It is important to know if and what impacts those potential threats have on the overall groundwater quality.


To get a good representation of the conditions around the lake, wells in different aquifers were chosen based upon location, past data and depth.  Chosen wells were in both the north and south watershed areas of Geneva Lake.  The groundwater shed boundary on the north side of Geneva Lake runs very close to the north shore of the lake.  On the south side of the lake the groundwater shed runs up to three miles south of the lake on the southwest end of the lake and around a mile on the southeast end of the lake.  A major portion of the Geneva Lake watershed extends southwest of the lake out into the Big Foot Prairie (Figure 2).


Depth of wells tested ranged from 84 ft. to 804 ft.  Aquifers in the Geneva Lake area include the glacial outwash and till consisting of sand and gravel that range between 0 -  200 ft. and is found throughout the basin; Silurian dolomite, a limestone aquifer that exists as a thin layer just below the sand and gravel on the eastern end of the lake found at depths between 175 and 200 ft. and a Sandstone aquifer found below 200 ft.  Between the limestone and the deep sandstone aquifer is the Maquoketa shale confining unit found only on the eastern half of the lake.  Being a shale, this layer does not serve as an aquifer (Figure 3).

hydrogeology of SE WI.jpg


Wells 1, 3, 4, 5, 6, 10, 11, 12 and 13 are drawing from the sand and gravel aquifer.  Well 7 is the deep sandstone aquifer. The depths of wells 2, 8, and 9 are unknown.   A better idea of the aquifer that each well draws from can be obtain by reviewing the well drilling log.  Not all well logs were found for the wells tested. 


Of the 13 private wells tested in 2020 one had a positive total coliform but tested negative for E-coli (fecal coliform).   None of the thirteen private wells tested exceeded the nitrate nitrogen drinking water standard.  Only four wells had levels that were above detection levels,  and they were below the drinking water standard (Table 1). 

Table 1. Private Well testing Results, Geneva Lake Watershed Walworth CO. WI 2019 and 2020

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In addition to the private wells tested in this program thirteen public water supply systems were also looked at in terms of nitrogen and bacterial test results. Public water supply wells include municipal wells, restaurants, bars, hotels, schools, and subdivision wells.   Public water supply systems are required to annually test their water for a wide range of parameters including nitrate nitrogen, total and fecal coliform bacteria.


The public water supply wells included in this report are located to the south, west and north of Geneva Lake.  Not all well depths were recorded, yet those recorded are of various depths ranging from 86 ft. at Kikkoman foods west of the lake, to 1500 ft. at South Shore Club located on the south shore of Geneva Lake.


The 2020 testing of these thirteen wells found bacteria to be absent and nitrate nitrogen to be below the drinking water standard (Table 2).  It should be noted that the highest two nitrate values found in the thirteen public water supply wells are located in the western portion of Geneva Lake’s groundwater shed, in an area of agriculture land use. 

Table 2.  Public Well Testing Results, Walworth County.

public well results 2020.png

Starry Stonewort Management  on Geneva Lake 

With the discovery of starry stonewort in Geneva Lake at several locations in the southeast corner of the lake outside the lagoon, starry stonewort’s  best long-term management shifted from eradication to containment and control. Management is concentrating in the areas of known starry stonewort populations.   

Long term management is anticipated to include controlling this invasive through chemical treatment, hand pulling and possibly a few other options that are being tried on other lakes.   As with a terrestrial environment, the best way to keep unwanted weeds from spreading in your lawn is to have a healthy lawn. It is the same with unwanted weeds in the lake.  Keeping  a healthy bio-diverse and balanced plant community will deter any unwanted weeds from establishing themselves and spreading throughout the lake.  


Educational effort with boaters at the launch and the cleaning of boats before and after they enter the lake will help keep unwanted invasive species from getting into the lake and spreading.  Keeping a clean boat while on the lake, such as removing vegetation and mud from anchors and props before you move to another site is one sure way of reducing the spread of an invasive within a lake.   This is the message of the Clean Boats Clean Waters program which was active on Geneva Lake's five municipallaunches duirng 2020.  The possibility of establishing a boat cleaning station is also bering explored.  For information on the regulations for boat transfer and bait laws  see  https://dnr.wi.gov/topic/Invasives/boat.html.

For 2021 a shorline meander plant survey is being planned.  The survey will look at the plantcommunity in the shorline area of the lake, especialy near the launch sites.  

Future starry stonewort populations in Geneva Lake will also be managed to control and contain.  Starry stonewort management will be based upon an integrated pest management approach that looks at the big picture of keeping a healthy lake and specifically, a healthy plant community.  


A long term commitments to Clean-Boats Clean Waters ( ttps://dnr.wi.gov/lakes/cbcw/) practices at the launches are a must if we are to reduce the likelihood of new invasive species getting into Geneva Lake.   During the summer of 2020 the GLEA staff the municipal public launch sites with individuals trained in the Clean Boats, Clean Waters program to help boaters understand what they must do to help spread aquatic invasive species.