Wetland Restoration and Creation for Nitrogen Removal: Challenges to Developing a Watershed-Scale Approach in the Chesapeake Bay Coastal Plain

Abstract

Abstract Concern for the health of the Chesapeake Bay and the establishment of the Bay Total Maximum Daily Load have led to growing interest in restoring and creating wetlands to mitigate agricultural nitrogen inputs. All Bay states have included wetland restoration in their watershed implementation plans (WIPs) to help meet their required reduction in nitrogen loading. In agricultural areas of the coastal plain, efforts to develop a watershed-scale approach to siting and designing wetlands have been met with considerable challenges. Nitrate loss is primarily attributed to base-flow conditions, and groundwater flow is multidimensional and highly variable, so accounting for nitrate transport connectivity between agricultural N source areas and potential wetland restoration areas is difficult. Socioeconomic and political challenges also constrain implementation. Our ability to account for subsurface connectivity may be improved with better assessment of hydrologic connectivity in areas with artificial drainage, catchment-scale studies of hydrogeomorphic predictions of hydrologic connectivity, and improved use of geospatial data. A coordinated monitoring program would improve our ability to estimate wetland nitrogen removal efficiencies across environmental and management conditions. The addition of a requirement that water quality should be an explicit objective of restorations included within WIP accounting would avoid the inclusion of projects with minimal water quality benefits. Research is also needed on farmer attitudes in the Chesapeake Bay watershed toward wetlands for water quality protection. These proposed actions would improve our ability to understand and implement wetland restoration as a component of our response to meet water quality objectives.