Delavan Lake Report

Delavan Lake Sanitary District
Delavan Lake Improvment Association
Delavan Lake Water Quality
Delavan Lake USGS

2021 State of the Lake Report

2021 State of the Lake

Town of Delavan Lake Projects (updated: 8/12/19)

Town Park Project 1 - PHASE 2

This project will start Summer of 2020

Grant request has been submitted to the DNR, and DNR has been approved

Below is the timeline for this project


June 15-16 Installation Erosion Control & De-watering by R&T Voegeli Excavating
June 17 Clearing and Grubbing by R&T Voegeli Excavating
June 18-19 Excavate site to Proposed Grade by R&T Voegeli Excavating
June 22 Install Sand Bedding by R&T Voegeli Excavating
June 23-24 Install Geo Textile and Granite Boulders by R&T Voegeli Excavating
June 25 Excavate and Install Rip Rap by Culvert by R&T Voegeli Excavating
June 26 Restore site with seed and erosion mat by Jeff Voegeli Landscaping Inc.
June 29-30 Final Cleanup and Rain Day Extension by All

Town Park Project 1 - PHASE 2


News from Delavan Lake Sanitary: Aug 19, 2019

Purple Loosestrife now blooming near Delavan Lake

Purple Loosestrife, Lythrum salicaria, is an extremely invasive wetland species that was introduced to the United States form Europe as a garden perennial. Plants grow from 3 - 10 feet tall and a single plan can easily produce 2 million seeds per year. These aggressive plants have spread to wetlands, lake and stream edges, road ditches and other wet areas where their intense grown can quickly out compete native plants.

Purple Loosestrife is listed as a Restricted Species in Wisconsin, which means it is illegal to buy, sell or cultivated this plant.

We are asking everyone to be on the lookout for Purple Loosestrife and if you find it on our property please use one of the suggested control measures to eradicate it.

Control: Manual control for smaller plants means pulling or digging plants. Cut stems often form new roots and flower spikes disposed of on the ground will continue to mature and produce seeds. Please place all cut and dug plants into a garbage bag for removal to a landfill.

Chemical control may work as well. Check with the DNR invasive species staff for the latest
Purple Loosestrife chemical control information. Since Purple Loosestrife is usually near water, a permit will likely be required from the Wisconsin Department of Natural Resources (DNR).

For larger populations, Wisconsin has a very successful bio-control program to help control (not eradicate) purple loosestrife. The bio-control agents include 2 species of insects that feed on the shoots and leaves of the purple loosestrife plants. Overtime the plants are weakened to the point that they produce smaller plants with fewer stems and many eventually die. White we are seeing significant control of this species it is still extremely important that no new plants are introduced and that existing populations are carefully monitored.

For more information please see the DNR Fact Sheet at



​The Delavan Lake Water Quality program, jointly financed by the Delavan Lake Sanitary District, the Town of Delavan, and the United States Geological Survey includes monthly monitoring of the lake and its watershed. It also includes the gathering of upstream "loading" data from an automated sampling station on Jackson Creek, and sampling from 8 strategically located stream crossings throughout the watershed. The purpose of the comprehensive monitoring program is to systematically gather the information which the Lake Committee and its expert advisers require to evaluate and guide its ongoing efforts to maintain and improve lake water quality.​

The 0.80 inch rainfall and the gradual snowmelt provided the perfect opportunity to conduct the first of 8 regularly scheduled sampling efforts in carefully identified locations around the lake's extensive watershed. The sampling is conducted according to strict protocols and the staff charged with the responsibility for collecting the samples has received extensive training by skilled USGS personnel. The samples, 2 from each of the 8 sites are sent to CT Laboratories in Baraboo WI for analysis. The lab is fully certified by cognizant state and federal agencies. Additionally, members of the team reviewed their capabilities. You can check them out at Five separate analyses are conducted on each sample. They include, total phosphorous, total nitrogen, and suspended solids. The resultant information is then forwarded to each of our team members for interpretation. Should one location or another indicate a particularly high concentration of nutrients or suspended solids, the team will further evaluate conditions "upstream" in an effort to identify the source of the elevated loadings, and recommend specific actions to remediate the problem area.​

An essential part of the watershed monitoring program is the automated sampling site at Jackson Creek maintained by the USGS as an integral part of the Comprehensive program. Jackson Creek accounts for an estimated 68% of all water and approximately 75% of the total phosphorus entering Delavan Lake. The station measures stream flow in real time and the chart below clearly shows the impact of the rainfall and melting over the first weekend in March.

The automated sampling system will obtain samples of the incoming stream water both routinely and at peak flow periods. The samples will be subsequently analyzed for suspended sediment, dissolved phosphorous, sediment particle size and Nitrogen. The aggregated information will yield estimates of nutrient loading which can be readily compared to historical data. The Mound Road Sedimentation Ponds, which were rebuilt in 2009, are a critical part of the Lake protection system and the data resulting from both sets of sampling will provide useful management data. The Lake Committee intends to conduct a detailed study of the rate at which sediment has been accumulating in the rebuilt sediment and nutrient control ponds this spring. The information gathered at the station will complement sampling at the route 50 bridge which will in turn provide insight into the effectiveness of the recently completed Inlet dredging project.​

The In-Lake element of the program is already underway. The first sampling was conducted by USGS staff in February (yes, through the ice). The second sampling will take place as soon as practicable after the ice leaves the Lake. The samples will be analyzed along distinct and meaningful parameters. The results, as was the case last year, will be reported as they become available on the Towns website under the Lake Information tab. We are actively working with others to reliably summarize this data in a simple set of “dashboard measures”. The task has proved to be more complex that we anticipated. Nevertheless, we hope to have that “dashboard” in place by early summer.​

Dale M. Robertson – USGS Wisconsin Water Science Center