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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #333133
Title: Design and hydrologic performance of a tile drainage treatment wetland in Minnesota, USA

Author
item LENHART, CHRISTIAN - University Of Minnesota
item GORDON, BRAD - University Of Minnesota
item NIEBER, JOHN - University Of Minnesota
item Gamble, Joshua
item CURRENT, DEAN - University Of Minnesota
item ROSS, NIKOL - Minnesota Department Of Agriculture
item KARLHEIM, LYDIA - Tetra Tech
item PETERSON, HEIDI - Minnesota Department Of Agriculture

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2016
Publication Date: 11/25/2016
Citation: Lenhart, C., Gordon, B., Nieber, J., Gamble, J.D., Current, D., Ross, N., Karlheim, L., Peterson, H. 2016. Design and hydrologic performance of a tile drainage treatment wetland in Minnesota, USA. Water. 8(12):549. doi:10.3390/w8120549.

Interpretive Summary: Constructed treatment wetlands in can intercept flow from tile drained agricultural fields and remove nitrate prior to discharging to streams or ditches. Fitting wetlands into riparian zones and land adjacent to ditches to minimize farmland usage and the associated costs of easements or land purchase may increase landowner adoption. We sought to develop a new treatment wetland design and then model and monitor its effectiveness. After construction in 2013 the wetland was monitored for three years. Nitrate removal averaged 68% over 3 years, nearly matching model predictions. However most denitrification occurred in the sub-soil of the wetland rather than in surface flow as predicted. The wetland had similar nitrate removal rates to other studies in the region. The edge-of- field design provides advantages such as greater potential landowner adoption in rural areas. The finding is important for the design of treatment wetlands because it demonstrates that small, edge-of-field designs can be as affective as larger basins in removing nitrate from tile drianage water, but also suggests possible ways to further improve removal. The findings of this research will be of interest to NRCS who have developed a treatment wetland standard, watershed districts, researchers, and producers/producer groups with interest in reducing tile drainage nitrate losses.

Technical Abstract: Treatment wetlands are increasingly needed to remove nitrate from agricultural drainage water to protect downstream waters such as the Gulf of Mexico. A 0.10 ha wetland was designed,installed and monitored to treat subsurface drainage flow from farmland in Minnesota, USA. This project sought to develop a new treatment wetland design and then model and monitor its effectiveness. A level-pool routing, mass balance approach with Drainmod flow inputs was used to predict nitrate removal efficiency. After construction in 2013 the wetland was monitored for three years recording flow inputs and outputs in addition to nitrate-nitrogen, total phosphorus and orthophosphrous into and out of the wetland. Nitrate removal averaged 68% over 3 years; nearly matching model predictions. However most denitrification occurred in the sub-soil of the wetland rather than in surface flow as predicted. The wetland had similar nitrate removal rates to other studies in the region. The edge-of- field design provides advantages such as greater potential landowner adoption in rural areas.