Harvesting

Harvesting is currently the best management option that the MPRB has to control aquatic plants, including Eurasian watermilfoil, an aquatic invasive species that is prevalent in many Minneapolis lakes.  Harvesting is done primarily in high recreational use areas such as the beaches and boat launches.  Harvesting temporarily provides for trouble-free boating and swimming, and allows sunlight to penetrate to native plants below.

Harvesting of aquatic plants can only occur in the areas identified in the Minnesota DNR issued permit. The Aquatic Plant Management Permit allows for up to 50% of the littoral zone to be harvested.  The littoral zone is the near shore area where sunlight penetrates all the way to the bottom and aquatic plants grow.  The MPRB uses two forms of harvesting as part of its aquatic plant management program – mechanical harvesting and hand pulling by SCUBA divers.

2019 Harvesting Permit Maps

Mechanical Harvesting

Mechanical harvesting is performed on Cedar Lake, Lake of the Isles, Bde Maka Ska and Lake Harriet.  A machine called a mechanical harvester, operated by MPRB certified equipment operators,  removes plants that are in the top four to six feet of water. The harvested plant material is removed from the water and stored until the end of summer when it is brought to the Minnesota Landscape Arboretum to be used as organic fill for their operations.  The mechanical harvesters can only harvest within the Minnesota DNR permitted areas.  This means you won’t see them operating out in the middle of the deeper water or along the entire shoreline.

The harvesters operate throughout the season with changes due to the weather, wind, water temperature, plant growth rates, and other changing variables. The harvesters are operated by MPRB Equipment Operators who are professional drivers holding Class A Commercial Driver’s Licenses.

Lake Name

Hours of Operation in 2019 Distance covered in 2019 (miles) Tons of Material Removed in 2019

Bde Maka Ska

75.2 88.1 69.82

Cedar Lake

9.6 13.0 10.27
Lake Harriet 132.37 243.3

115.00

Lake of the Isles 33.23 33.3

26.70

TOTAL 250.4 377.7

221.79

Table Updated Monthly-Last Update August 1, 2019

Map of 2018 typical weed harvester activity for week of 7/30/2018-8/6/2018 at Lake Harriet

SCUBA Diver Hand Pulling

SCUBA diver hand pulling of aquatic plants is performed in areas that are inaccessible or hard to reach with a mechanical harvester.  SCUBA diver removal is utilized at Wirth Lake and Lake Nokomis.