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Twin Lakes Subwatershed Improvement

Growing Wetland Plants To Improve Water Quality

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About this project: 

Stormwater pondThe aquatic vegetation plantings were one part of the Twin Lakes Subwatershed Improvement Project - a water quality improvement project supervised by the Minnehaha Creek Watershed District (MCWD). The project was a coordinated effort by the Clean Water Partnership (CWP), which included representatives from the MCWD, the cities of Minneapolis and St. Louis Park, the Minneapolis Park and Recreation Board, Hennepin County and the Minnesota Pollution Control Agency.

Earlier components of the project included construction of wetland detention basinsWetlands are a key to many of the MCWD's and CWP's water quality projects because they naturally filter and cleanse urban stormwater.

The Chain of Lakes Clean Water Partnership was a seven-year initiative to improve water quality in the Minneapolis Chain of Lakes. It was one of the largest urban watershed-restoration projects in the country and included wetland restorations, storm sewer improvements and public education.

The project was funded and sponsored by the cities of Minneapolis and St. Louis Park, Hennepin County, Minneapolis Park and Recreation Board, MCWD and Minnesota Pollution Control Agency. The plantings were completed in 2004.

Where are the Plantings?

Plantings took place just west of Cedar Lake in Minneapolis and St. Louis Park. Aquatic vegetation was planted at Twin Lakes and Twin Lakes Park, while both aquatic vegetation and shoreline vegetation plantings took place at Cedar Meadows. 

Who was Involved?

  • MCWD directed the project, with help from members of the CWP and from the Cedar-Isles-Dean Neighborhood Association (CIDNA).
  • The Loring-Nicollet-Bethlehem youth volunteers, a group of 13- to 17-year-olds with an interest in the environment and horticulture, helped with plantings at Cedar Meadows.
  • Master gardeners from Twin Cities garden clubs helped train the youth volunteers and oversee the plantings.

How Do Aquatic Vegetation and Wetlands Enhance Water Quality?

While the MCWD and CWP tackle major water quality projects, backyard gardeners who have bodies of water on their properties (ponds, creeks, etc.) can use the same vegetation techniques to protect water quality on their properties and beyond.

By planting more than 19,000 select plants, the CWP completed shoreline and wetlands environs that naturally filter and cleanse urban stormwater. Wetlands effectively reduce levels of sediment, lawn pesticides, yard waste and nutrients - especially phosphorus - before they can impair lake water quality.

These urban water bodies need special wetland species - plants that are equipped to take on urban stormwater. These plants will grow rapidly and establish a defensive front against pollution. Their roots host beneficial bacteria that capture impurities.

Eventually, wetlands can improve the water quality of Twin Lakes and Cedar Lake by removing up to 30 percent of the phosphorus and dissolved inorganic nitrogen. Wetlands also are a haven for vast numbers of wildlife. In fact, the biodiversity of wetlands in the Midwest is greater than any other temperate plant community.

This particular project won't solve all the water quality problems. The combination of wetland ponds and sediment removal Best Management Practices has an immense, positive cumulative effect on improved water quality.

Approximately 19,000 plants (a mixture of 2" and 4" potted plants) were planted along the shorelines with small hand trowels. Protective barriers were built to keep Canadian geese, musk rats, white-tailed deer, carp and rusty crayfish from disturbing the plants, and to dissuade humans from trampling or pulling them.

Currently MCWD performs vegetation maintenance on the Twin Lakes pond buffer vegetation and the Cedar Meadows pond buffer vegetation. In the spring of 2011, a prescribed burn took place at both sites. Each site also goes through routine mowing, hand pulling and herbicide applications to keep invasive species out of the buffer.