Open AccessWetland restoration yields dynamic nitrate responses across the Upper Mississippi river basin
Author(s) -
Grey R. Evenson,
Heather E. Golden,
Jay R. Christensen,
Charles R. Lane,
Adnan Rajib,
Ellen D’Amico,
David Tyler Mahoney,
E. White,
Qiusheng Wu
Publication year - 2021
Publication title -
environmental research communications
Language(s) - English
Resource type - Journals
ISSN - 2515-7620
DOI - 10.1088/2515-7620/ac2125
Subject(s) - wetland , environmental science , hydrology (agriculture) , drainage basin , structural basin , tile drainage , nitrate , water resource management , ecology , geography , geology , soil water , soil science , geotechnical engineering , cartography , biology , paleontology
Wetland restoration is a primary management option for removing surplus nitrogen draining from agricultural landscapes. However, wetland capacity to mitigate nitrogen losses at large river-basin scales remains uncertain. This is largely due to a limited number of studies that address the cumulative and dynamic effects of restored wetlands across the landscape on downstream nutrient conditions. We analyzed wetland restoration impacts on modeled nitrate dynamics across 279 subbasins comprising the ∼0.5 million km 2 Upper Mississippi River Basin (UMRB), USA, which covers eight states and houses ∼30 million people. Restoring ∼8,000 km 2 of wetlands will reduce mean annual nitrate loads to the UMRB outlet by 12%, a substantial improvement over existing conditions but markedly less than widely cited estimates. Our lower wetland efficacy estimates are partly attributed to improved representation of processes not considered by preceding empirical studies − namely the potential for nitrate to bypass wetlands (i.e., via subsurface tile drainage) and be stored or transformed within the river network itself. Our novel findings reveal that wetlands mitigate surplus nitrogen basin-wide, yet they may not be as universally effective in tiled landscapes and because of river network processing.