A study published in the journal Nature Geoscience provides new understanding on the efficiency of wetlands within a watershed in mitigating harmful chemicals in rivers and streams.

• A team of researchers from the University of Minnesota looked at effective strategies on reducing nitrate at the landscape scale.
• In conducting the study, the research team used water samples gathered for four years from more than 200 waterways within the intensively managed Minnesota River basin, a 17,000-square-mile region of the Mississippi River basin.
• They also used geo-spatial information regarding land use in the watershed.
• Results revealed that when stream flows are high, wetlands are five times more efficient per unit area at decreasing nitrate than the best land-based conservation practices, such as cover crops and land retirement.
• In addition, the arrangement of wetlands within a watershed is an important predictor of the magnitude of nitrate reduction. Wetlands are three times more efficient at nitrate reduction if they intercept 100 percent of the drainage area in comparison to interception of 50 percent of the drainage area.
• Nitrate removal due to temporary wetlands, such as riparian floodplains and more geographically isolated wetlands, was measurable and was greatest during high stream flows. This was seen when such features are hydrologically connected to surface water.
• The researchers suggested that the restoration of wetlands could be one of the most efficient methods for comprehensive improvement of water quality.

In conclusion, the findings indicated that maintaining or restoring wetlands in intensively managed agricultural watersheds would reduce nitrate in rivers and improve water quality.

For the full text of the study, go to this link.

Journal Reference:

Hansen AT, Dolph CL, Foufoula-Georgiou E, Finlay JC. CONTRIBUTION OF WETLANDS TO NITRATE REMOVAL AT THE WATERSHED SCALE. Nature Geoscience, 2018; 11(2): 127-132. DOI: 10.1038/s41561-017-0056-6