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Wetland-Mediated Nitrate Dynamics across the Upper Mississippi River Basin
Citation:
Golden, H., J. Christensen, AND C. Lane. Wetland-Mediated Nitrate Dynamics across the Upper Mississippi River Basin. Joint R5/R7 Science Academy Webinar, Durham (virtual), NC, November 07, 2023.
Impact/Purpose:
Our work focuses on simulating and analyzing the downstream effects of NFWs at two scales: the ~0.5 million km2 Upper Mississippi River Basin (UMRB) and the Raccoon River Watershed (~9400 km2), Iowa. In the UMRB we ask: (1) what is the potential for NFWs to reduce nitrate within UMRB subbasins as well as at the UMRB outlet and (2) what NFW and NFW catchment characteristics influence nitrate reductions at these scales? Our more recent focus in the Raccoon River Watershed is to address how far downstream nitrate reductions from restored NFWs will affect water quality. Overall, we find that NFW catchment area-to-NFW area ratios, tile drainage, and distances to watershed outlets – along with other wetland characteristics – are key factors in determining the magnitude of NFW-mediated nitrate reductions, at both river basin (UMRB) and watershed (Raccoon River) scales.
Description:
Wetland restoration and construction are important land management options for retaining nitrogen and phosphorus and thereby improving water quality at local scales (i.e., at nearby streams). However, limited information exists regarding the cumulative influence of wetlands outside of floodplains (i.e., non-floodplain wetlands, NFWs) on surface water quality at large river basin and watershed scales. Our work focuses on simulating and analyzing the downstream effects of NFWs at two scales: the ~0.5 million km2 Upper Mississippi River Basin (UMRB) and the Raccoon River Watershed (~9400 km2), Iowa. In the UMRB we ask: (1) what is the potential for NFWs to reduce nitrate within UMRB subbasins as well as at the UMRB outlet and (2) what NFW and NFW catchment characteristics influence nitrate reductions at these scales? Our more recent focus in the Raccoon River Watershed is to address how far downstream nitrate reductions from restored NFWs will affect water quality. Overall, we find that NFW catchment area-to-NFW area ratios, tile drainage, and distances to watershed outlets – along with other wetland characteristics – are key factors in determining the magnitude of NFW-mediated nitrate reductions, at both river basin (UMRB) and watershed (Raccoon River) scales.
