Floating gardens don’t just look idyllic. They can also have a measurable, positive impact on water quality, as a new study has demonstrated.
Floating gardens are essentially rafts built on a frame of plastic caging, wrapped in coconut husks, and filled in with native plantings. As plants grow, they extend their roots into the water, growing hydroponically, explains a statement.
On Chicago’s North Branch of the Chicago River, non-profit Urban Rivers and partners are developing a mile-long, floating eco-park. Dubbed the Wild Mile, the re-development of this former industrial canal is Urban Rivers’ flagship project. As part of the park, floating gardens, attached to shore, are being installed.
The Illinois State team, from the University’s Department of Geology, Geography, and the Environment, saw an ideal setup for a controlled experiment. “We got involved because it’s the perfect opportunity to see if there’s an impact on water quality,” explains lead author Abigail Heath in the statement.
Starting in spring 2018, Heath and co-authors sampled water immediately upstream and downstream of a narrow 3 meter by 50 meter floating garden installed along the shoreline. Although the garden is set at the edge of Chicago’s urban core, water quality is also impacted by upstream agriculture. Analyses are focused on nutrients including nitrate as nitrogen, chloride, sulfate, and phosphate.
An average of data collected over the course of the study show modest but definitive improvement. For example, nitrate as nitrogen dropped from 4.69 milligrams per liter in surface water just upstream of the garden to 4.43 milligrams per liter just downstream, a drop of about 1 percent. Phosphate was also lower downstream of the garden.
The researchers see this as a scalable model for how larger floating gardens might help remediate water in similar settings.
Image credit: Keira McPhee, flickr/Creative Commons