WetlandNNI: Quantification of hydrologic interception of nitrogen and phosphorus (National Nutrient Inventory) by conterminous U.S. wetlands (1987-2017)

Wetlands provide numerous critical functions, including nutrient cycling and water quality improvement, that have made them a critical component of many state and local stewardship programs. Quantifying landscape nutrients entering wetlands comprises crucial components of state-led efforts to improve nutrient reduction strategies, both for water quality within wetlands themselves and for other water sources, such as lakes and streams, that wetlands provide a buffer for nutrient inputs. However, these data are rarely assembled at comprehensive scales that are relevant to management, such as local wetland basins, stream catchments, watersheds. This subproduct provides downscaled data from EPA's National Nutrient Inventory (NNI; https://www.epa.gov/water-research/national-nutrient-inventory-portfolio) for approximately 84 million individual wetland basins over a 30-yr period accumulated for individual wetland basins, local stream catchments and full accumulative watersheds across the conterminous US. We generated annual landscape nitrogen and phosphorus inputs from several anthropogenic sources across nearly 12 million wetland basins at 5-yr increments from 1987-2017 (1987, 1992, 1997, 2002, 2007, 2012, 2017), resulting in a novel and robust resource to explore effects of nutrient inputs on wetlands and the effect of wetland interception of landscape nutrients on other water resources. The new metrics cover all major anthropogenic sources of urban and agricultural nutrient inputs, including nitrogen and phosphorus metrics from livestock manure excretion, crop removal, and fertilizer. The accessibility of these data will greatly advance the way state partners generate nutrient budgets for impaired waters and conduct conservation and restoration planning to meet statutory requirements under the Clean Water Act.