Floating Gardens: More than Just a Pretty Place
Boulder, Colo., USA: Floating gardens sound so idyllic. Now, a study proves
that they are more than just a pretty place. The study, by researchers at
Illinois State University, demonstrates that such constructed gardens can
have a measurable, positive impact on water quality.
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. 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 primary intent of the floating gardens is beautification. But 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.
Heath will present the results of the study in an online talk on Tuesday
from 10:45 to 11:00 a.m. EDT, during the Geological Society of America’s
annual meeting.
The study is novel: previous studies have explored floating gardens’ impact
on water quality over time, primarily in wastewater treatment ponds, but
not over space, in moving water. The project also meshes well with Urban
Rivers’ broader goals. “The city is interested in water quality,” says Phil
Nicodemus, Urban Rivers Director of Research. “Happily, Illinois State got
involved.”
Starting in spring 2018, Heath and co-authors have sampled water
immediately upstream and downstream of a narrow 3 meter by 50 meter
floating garden installed along the shoreline. Samples are collected
weekly, at the surface and from 0.3 meters deep, the depth where roots
reach from the garden’s base into the water. 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.
Could this small slice of human-made paradise improve water quality? 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.
“Despite how small this garden was there was measurable improvement in
water quality from upstream to downstream, especially for nitrates,” notes
Heath. She and colleagues see this as a scalable model for how larger
floating gardens might help remediate water in similar settings. “Even this
tiny garden makes a difference,” she says.
Contact: Abigail Heath
Illinois State University
Department of Geography, Geology and the Environment
Felmly Hall 206
Campus Box 4400
Normal, Illinois 61790-4400
aheath1@ilstu.edu
Phone (Dr. Eric Peterson): 309-438-7865
FEATURED ABSTRACT:
60-4:
Assessment of Floating Gardens to Improve the Water Quality of the
Chicago River
(10:45 a.m. EDT):
https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/355783
The Geological Society of America, founded in 1888, is a scientific society
with over 20,000 members from academia, government, and industry in more
than 100 countries. Through its meetings, publications, and programs, GSA
enhances the professional growth of its members and promotes the
geosciences in the service of humankind. Headquartered in Boulder,
Colorado, GSA encourages cooperative research among earth, life, planetary,
and social scientists, fosters public dialogue on geoscience issues, and
supports all levels of earth-science education.
https://www.geosociety.org
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