Building wetlands along waterways best option to deter runoff from Midwest crop fields

Research project searches for cost-effective intervention alternatives

By: - July 11, 2021 9:00 am

New research indicates building large wetlands is the most cost-effective way to deter chemical runoff and soil loss on crop fields in the Midwest. The study centered on the Le Sueur River Basin in Minnesota where wetlands help respond to runoff and erosion from corn and soybean fields. (Amy Hansen)

LAWRENCE — The most cost-effective method of responding to chemical and sediment runoff from intense agriculture production is development of large-scale wetlands in watersheds feeding rivers and large streams, a University of Kansas researcher said in a new study.

Findings of research published in Proceedings of the National Academy of Sciences indicated the most effective environmental intervention should be concentrated at the watershed level rather than on individual farms. Conclusions were dawn from computer modeling of the Sueur River Basin in Minnesota, which is subject to runoff from corn and soybean fields.

Excess nitrogen and phosphorus can wash from fields and into waterways by rain or melting snow and can leach through the soil to groundwater. Typically, a farmer in Kansas or other Midwest state striving to deter soil loss and protect water quality would plant cover crops, reduce tillage, adopt high-precision fertilizer application or add modest water retention ponds.

A study of the Le Sueur River Basin in Minnesota, which is subject to runoff from agricultural production of soybeans and corn, says wetlands constructed along waterways are the most cost-effective method of reducing nitrate and sediment loads in streams and rivers. Authors say the research is applicable to other Midwest farm states. (Amy Hansen)

Amy Hansen, assistant professor of civil, environmental and architectural engineering at KU and lead author of the study, said these useful methods of intervention relied on through voluntary participation of farmers and a patchwork of government agencies. However, she said, it wasn’t as effective environmentally and less attractive economically than constructing wetlands feeding into a common waterway.

She said wetlands were beneficial because they slowed movement of water heading to streams, rivers or lakes and contained microbes or vegetation that processed nutrients used as fertilizer on crops.

“Microbes and plants within wetlands are actually removing the nitrate from the water,” Hansen said. “With sediment, on the other hand, what the fluvial wetlands are doing is holding water back during these high flows — and by holding that water back you’re getting lower peak stream flows, which is reducing the amount of near channel sediment that’s being transported downstream.”

Grappling with an entire watershed requires combining funds from different agencies and pinpointing locations where wetlands offer the greatest reduction in nitrates and sediments reaching waterways, said Jacques Finlay, a professor of biological sciences at the University of Minnesota.

“This work shows that we can’t make real progress toward our goals for improving water quality in agricultural areas with more of a business-as-usual approach,” Finlay said.

The proof-of-concept research funded by the NSF and involving the universities in Kansas and Minnesota as well as University of California-Irvine relied on multidisciplinary expertise of social scientists, hydrologists, ecologists and environmental economists, said Efi Foufoula-Georgiou, of UC-Irvine.

“The sustained NSF support allowed us to take a fresh view of the problem and take the time needed to collect extensive field data, build new models and engage with stakeholders,” Foufoula-Georgiou said.

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Tim Carpenter
Tim Carpenter

Tim Carpenter has reported on Kansas for 35 years. He covered the Capitol for 16 years at the Topeka Capital-Journal and previously worked for the Lawrence Journal-World and United Press International. He has been recognized for investigative reporting on Kansas government and politics. He won the Kansas Press Association's Victor Murdock Award six times. The William Allen White Foundation honored him four times with its Burton Marvin News Enterprise Award. The Kansas City Press Club twice presented him its Journalist of the Year Award and more recently its Lifetime Achievement Award. He earned an agriculture degree at Kansas State University and grew up on a small dairy and beef cattle farm in Missouri. He is an amateur woodworker and drives Studebaker cars.

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