Mechanized aquatic plant management

In order to protect diverse and stable communities of native aquatic plants and prevent the spread of invasive aquatic plants, many aquatic plant and algal management and nuisance control activities require one or more permits issued by the department.

As a general rule of thumb, DNR permits are required if you are placing a structure in the water or disturbing the lake or river bottom. Removal of aquatic or riparian plants through hand removal, mechanical harvesting, raking or cutting may also require a mechanical aquatic plant management permit. Contact your local aquatic plant management coordinator or waterway resource management specialist before engaging in any aquatic plant management or nuisance control activities.

It is important to note that county zoning permits may also be required for the placement of these structures, or for electrical housing units that may be needed to support structural aquatic plant management units. Applicants are responsible to check with local county zoning staff to seek applicable county permits.

Aerators

Aeration systems can help increase the localized dissolved oxygen levels in the water column and circulate water to prevent algal buildup. These systems typically require placing a single base or tubular structure on the lakebed to push air or water through the water column so that water is continually moving, avoiding stagnant water flow conditions. This has the potential to push algal mats to other parts of the lake or river. This can adversely impact other riparian owners and members of the public who may be recreating on the water. Although the department does not advocate for aerators, a permit is not required to install or maintain these devices so long as the following conditions are met:

• the prop is attached to a legal structure that has either received a permit or is exempt from needing a permit;
• the mixing action does not disturb the lake bottom; and
• the prop does not cause problems for lake users or neighbors.

If any of the above conditions are not met, visit water permits to apply for a miscellaneous structure permit.

Beach grooming or mowing vegetation

Mowing vegetation along coastal waters may be exempt from permitting. See the shoreline maintenance exemption checklist for more information.

If the mowing activity requires motor vehicles to be driven on a lakebed to groom or mow the shoreline, an individual permit may be required. Visit water permits to apply for an individual permit. Permits may also be needed to drive motorized equipment on beaches to manage for invasive plants growing on the exposed lakebed. Visit beach maintenance for additional information on managing invasive plants, or visit water permits to apply for permits to drive motorized equipment on beaches.

Mowing with a push lawnmower on exposed lakebed is exempt from a NR 109 permit. If the area being mowed is confined to a single area with a maximum width of no more than 30 feet measured along the shoreline provided that any piers, boat lifts, swim rafts and other recreational and water use devices are located within that 30-foot-wide zone and may not be in a new area or added to an area where plants are controlled by another method. Any removal beyond the 30 feet would require a permit.

Diver-Assisted Suction Harvesting (D.A.S.H.)

DASH utilizes a similar suction device as suction harvesting, but the device is solely used to transport hand-picked target species by a diver to the surface, without the diver surfacing with the target species. The suction device basically serves as a conveyor to a boat or shore station where the target species is isolated and disposed of. The use of this technology will require a mechanical aquatic plant management permit to avoid deleterious impacts on the native aquatic plant community.

Fountains

The benefits of fountains are similar to aeration systems- they avoid stagnant water conditions and help maintain localized oxygen levels in the water column. Fountains spray water above the water surface whereas aerators are fully subsurface systems. Because a fixed structure must be placed on the lakebed to install a fountain, a miscellaneous structure permit is required.

Jetting

Jetting is a process of forcefully shooting water toward the lakebed to dislodge sediment and/or plants. The dislodged sediment typically moves from one area of a lake to another and can cause a number of environmental concerns including declining water clarity, nutrient release, destruction of fish and wildlife habitat, and increased sedimentation of neighboring properties or channels. Due to these potentially severe side effects, the jetting of sediment is classified as dredging and requires a DNR dredging permit.

Nursery growers licensed by DATCP can sometimes use jetting to collect native aquatic plants. An aquatic plant jetting general permit has been created to streamline the process for these types of jetting operations.

Mixing prop or other mixing devices

A mixing prop is a propeller suspended in the water column that moves water and suspended algal material away from a localized area. These props are typically attached to another structure such as a pier, wharf, boom or float. Although mixing props potentially reduce the density of isolated algae mats, the effort usually does not improve the overall water quality of the lake and does not remove all risk of exposure to algal toxins. It also can cause significant problems for downstream riparian owners that may receive compounding algal mat densities from the prop. Although the department does not advocate for mixing props, a permit is not required to install or maintain these devices so long as the following conditions are met:

• the prop is attached to a legal structure that has either received a permit or is exempt from needing a permit;
• the mixing action does not disturb the lake bottom and the discharge jet is below the water surface; and
• the prop does not cause problems for lake users or neighbors.

If any of the above conditions are not met, visit water permits to apply for a miscellaneous structure individual permit.

Rollers

Weed rollers are typically slow-moving pivot beams attach to a pier or wharf that slowly roll along a lake bottom, agitating lakebed material to prevent aquatic plant growth. Because these are submerged structures, they can potentially cause navigation concerns and can limit habitat availability for fish and aquatic life. For these reasons, rollers are not typically permissible in Wisconsin's waters. A miscellaneous structure individual permit is required if a riparian owner wishes to pursue a roller.

Suction harvesting

Suction harvesting is a process of suctioning lakebed to remove sediment and uproot and remove aquatic vegetation. Because you are disturbing and removing lakebed materials, this process is considered dredging and requires a dredging permit. The use of this technology will also require a mechanical aquatic plant management permit to avoid deleterious impacts on the native aquatic plant community.

Weed harvesting (mechanical harvesting)

Weed harvesters are boat-like structures that move across the water surface cutting and collecting aquatic plants. Mechanical harvesting requires a mechanical aquatic plant management permit unless the body of water is 10 acres or less and is entirely confined on the property of one person with the permission of that property owner.

Weed raking

A weed rake is a device that attaches to an existing structure such as a pier or piling, designed to mechanically remove aquatic plants by the movement of rake tines attached to a floating boom without grubbing, lifting or rolling of the bottom sediments. A weed rake general permit is available for qualifying weed rake projects. Projects that cannot meet the eligibility requirements of the general permit must apply for a miscellaneous structure individual permit.