Locations and Magnitudes of Nitrate Reductions from Wetland Restoration across the Upper Mississippi River Basin

Abstract:

Large-scale and long-term changes to land use and management have led to excessive eutrophication and degraded aquatic systems throughout the Upper Mississippi River Basin. Recommendations for improving the condition of the basin’s aquatic systems invariably include the restoration of some portion of the basin’s historical wetlands. Yet there is considerable uncertainty regarding the potential of wetlands to mitigate nutrient loads across larger spatial scales and in landscapes so extensively modified by human activity. We applied a basin-scale process-based hydrologic model to simulate the capacity of wetland restoration to reduce nitrate loads across the basin. We executed over 100 simulations to evaluate restoration efficacy across varying extents of wetland restoration and associated declines in fertilizer application given reduced quantities of land in agricultural production. Preliminary results indicate that restoration will reduce nitrate loads in the basin but that the magnitude of reduction is highly variable across the landscape’s subbasins. We identify subbasins simulated as providing higher nitrate load reductions while determining why the model predicted success in these locations in-particular. In so doing, we highlight generalized conditions for restoration success across the basin.