WetlandNNI: Quantification of hydrologic interception of nitrogen (National Nutrient Inventory) by conterminous U.S. wetlands (1987-2017)
Wetland restoration can be an effective tool in nutrient reduction strategies. However, to be effective as a strategy, restored wetlands must be geographically positioned where (1) soil and hydrologic conditions promote wetland persistence post-restoration and (2) interception of excess landscape nutrients by restored wetlands will occur. Understanding the distribution of restorable wetlands and the amount of nutrients these wetlands might intercept would provide critical insights that would allow managers to prioritize restoration actions when nutrient reduction is a primary objective. Further, understanding the potential accumulative effects of restorable wetlands across stream watersheds would further help to prioritize restoration activities within and among watersheds to maximize returns on investments. This subproduct will use several recently-developed EPA products to quantify the potential interception of landscape nutrients by existing and restorable wetlands. Specifically, these EPA products include geospatial depictions of: (1) the locations of restorable wetlands (EnviroAtlas Factsheet), (2) landscape nutrient inputs (EPA’s Nutrient Inventory), and (3) a geospatial framework that nests wetlands within catchment boundaries of the National Hydrography Dataset Plus version 2 (NHDPlusV2). This nested geospatial framework was developed by ORD’s Scott Leibowitz, Ryan Hill, and Marc Weber as part of a previous RAP to characterize wetland connectivity to downstream waters and a publication describing the framework is forthcoming. Briefly, the framework identified 6.6 million unique contiguous wetland units from the 2011 National Land Cover Dataset (NLCD). It then delineated wetland drainage basins for each wetland and associated flowpaths to the 2.6 million receiving streams of the NHDPlus. The wetland drainage basins and flowpaths can then be combined with other landscape layers (e.g., soils) to characterize features upslope or downslope from each wetland that can affect how wetlands connect or contribute to downslope waterbodies. In this effort, the framework would be updated with (1) the most recent version of the NLCD (e.g., 2019) and (2) potentially restorable wetlands. Wetland drainage basins would then be used to calculate summaries of nutrients inputs (Nutrient Inventory) draining to each existing and restorable wetland. Finally, the nesting of the wetlands framework within the NHDPlusV2 would allow for accumulations of restoration scenarios to be made and stored within EPA’s StreamCat dataset. Thus, this subproduct will produce searchable databases to support nutrient reduction through wetland restoration at two spatial scales: individual wetlands and receiving stream. Due to the large amount of data produced by this subproduct, work could also include modeling, visualization, and search tools to organize and help prioritize wetlands among possible restoration scenarios.