Lake Operations

Aquatic Plant Harvesting, Background and Current Plan Updates

See permits at the bottom of this page**


The Delavan Lake Sanitary District has been responsible for the performance and management of the mechanical harvesting of nuisance aquatic plants in Delavan Lake since 1997. In 2002 the Wisconsin Department of Natural Resources (WDNR) implemented new regulations which required DLSD to apply for and obtain a NR 109 permit for these harvesting operations. As a part of this permitting process we are required to submit a report on the harvesting operations conducted each season.

In 2009, we found that our harvested aquatic plant and algae quantities were down from what has been considered normal.  The details of quantities and types of plants harvested can be found in the Harvesting Report.  The complete Aquatic Plant Harvesting Report can be found at the bottom of this page.

Each year the Delavan Lake Sanitary District contracts with an Aquatic Plant Specialist to perform an Aquatic Plant Survey of Delavan Lake.  A copy of the latest survey (2012) is available at the bottom of this page.

View Aquatic Plan Surveys at the bottom of this page.

The first Aquatic Plant Management Plan was developed for Delavan Lake in 1993 with the assistance and approval of WDNR. The goal of this plan was to preserve the aquatic systems that included water quality, fisheries and wildlife, while minimizing the conditions resulting from aquatic nuisances, and to preserve and maintain recreational uses of Delavan Lake. The plan included mechanical harvesting and chemical treatments to minimize nuisance conditions and regular monitoring of changes within the aquatic plant communities which would provide guidance for the future harvesting program.

In 2002 a comprehensive lake management plan was completed for Delavan Lake. This planning report was prepared by the Southeast Wisconsin Regional Planning Commission (SEWRPC) and funded in part by a lake planning grant from WDNR. This report contained a revised Aquatic Plant Management Plan which was reviewed and adopted by the DLSD Commission as its official plan for lake management activities on Delavan Lake.

In 2008 DLSD received a grant to update this Aquatic Plant Management Plan, and we have again retained SEWRPC to assist us in this process. It is expected that revisions to this plan will be guided by the results of recent Aquatic Plan Surveys and Harvesting Reports as well new science and technology. It will be our goal to use the most efficient and environmentally sound means possible to accomplish the goals of the program.

Our current WDNR Harvesting Permit allows the mechanical harvesting of up to 349 Acres. This permit expires December 31, 2016.

We observed some major changes in aquatic growth during the 2008 harvesting season. How much of this was attributable to the periods of high runoff and high lake levels is uncertain. Runoff from upstream farm fields is extensive. The heavy rains hit in mid June and the crops were too young to do much to slow down the runoff. Aerial photos show vast areas of silt laden runoff coming to the lake. It is likely that much of the manure and chemicals used to feed local crops also ended up in the lake.

We had delays in the appearance of some Aquatic plant species and a reduction in the numbers of others; specifically Eurasian Water Milfoil, which is an invasive aquatic plant. The numbers of new beds of Wild Celery throughout the lake was striking. This is a valuable food source for water foul and we try to be careful not to cut it. That may be difficult as it is becoming established within the beds of nuisance plants that we usually cut. Wild celery breaks off from ducks feeding or boat traffic and the broken ends float or are wind driven into shore. We have received many new complaints about this.

The  Aquatic Plant Surveys and Harvesting Reports are available at the bottom of this page.

Large numbers of small zebra mussels were observed throughout the lake. They were colonizing any hard surface in the lake, from shore stations to watercraft and most of the plants that we were trying to harvest. The consequence of the large numbers of zebra mussels attaching themselves to plants is that the plants are weighed down and out of the reach of the harvesters. During the heavy rainfall events this summer, large quantities of small zebra mussels were flushed through the dam gates and downstream. Many have found new homes on the dam gate operating equipment.

In her 2008 Aquatic Plant Survey, Kathy Aron noted the very heavy growth of filamentous algae throughout the lake. It was attached to plants and came aboard during harvesting making our loads very heavy. This causes stress to our equipment as well as many more trips to dump weed loads.

  Weed Harvesting Crew 2017

Weed Harvesting Crew 2017



Document NameTypeSizeViewDownload
An Aquatic Plant Management Plan Update for Delavan Lake 2017
Adobe Acrobat File
2.96 MB
Aquatic Plant Harvesting Permit 2017
Adobe Acrobat File
10.03 MB
Harvesting Permit 2012-2016
Adobe Acrobat File
3.77 MB
Chemical Aquatic Plant Permit 2016
Adobe Acrobat File
3.46 MB
Chemical Aquatic Plant Permit 2015
Adobe Acrobat File
3.67 MB
Chemical Aquatic Plant Permit 2014
Adobe Acrobat File
2.24 MB
Chemical Aquatic Plant Permit 2013
Adobe Acrobat File
2.47 MB
Chemical Aquatic Plant Permit 2012
Adobe Acrobat File
3.49 MB
Aquatic Plant Harvesting Report 2014
Adobe Acrobat File
5.1 MB
Aquatic Plant Harvesting Report 2012
Adobe Acrobat File
5.74 MB
Aquatic Plant Harvesting Report 2013
Adobe Acrobat File
6.08 MB
Aquatic Plant Harvesting Report 2011
Adobe Acrobat File
5.79 MB
Aquatic Plant Harvesting Report 2009
Adobe Acrobat File
5.86 MB
Aquatic Plant Harvesting Report 2010
Adobe Acrobat File
5.66 MB
Aquatic Plant Survey 2013
Adobe Acrobat File
576.2 KB