Slowing the Flow: Wetlands Work As Filters
Nestled along farm fields on the banks of Money Creek, a series of wetland projects aims to improve water quality in McLean County.
“One of the big goals for this wetland is to reduce the amount of nitrates flowing into Lake Bloomington,” says McLean County farmland owner Tim Kraft, who installed a wetland on his land in 2014.
Money Creek is the main tributary to Lake Bloomington, one of the reservoirs used as a water supply for the city of Bloomington. The constructed wetlands act as filters, removing excess nutrients that can have a negative impact on water quality if they reach a high enough level.
Nitrates are a water soluble form of Nitrogen, an essential nutrient for plant growth. When heavy rains saturate the soil, nitrates can be washed away.
Nitrates occur naturally in the absence of agriculture, but fertilizer use can contribute to increased levels. Nutrient loss can be an unintended side effect of fertilizer needed for crop production and field tile drainage that make much of Illinois’ soggy soils farmable.
“Everyone has the same goal to keep the nitrogen in the field and out of the water,” says Rick Twait, Superintendent of Water Purification for the city of Bloomington. “The export of nitrates in tile drainage water doesn’t do anybody any good.”
In looking for solutions to keep nitrates out of the water, the city partnered with McLean County Soil & Water Conservation District, Nature Conservancy and the Environmental Defense Fund to explore wetlands. To learn more, check out this video on a similar project along the Mackinaw River:
As part of the ‘Drinking Watersheds’ project, monitoring equipment at the inlets and outlets of each wetland collect data for researchers to analyze how well the process is working.
“We’re seeing reductions of about 50 to 60 percent,” says University of Illinois Ecological Specialist, Mike Wallace, who visits each wetland about once a week to collect data and water samples. “No matter how much nitrate is in the water, the wetlands remove about half.”
In addition to reducing nutrients in water, wetlands serve can also serve a secondary purpose.
“The big emphasis is water quality, but a great side benefit is wildlife habitat,” Kirkham says.
To learn more, read the full article here.