Quantifying 30 Years of spatially explicit catchment and watershed nutrient budgets through the NNI in StreamCat

This presentation will discuss the benefits of incorporating the NNI into StreamCat, providing annual time series (1987-2017) of nitrogen and phosphorus inputs, removal by crop harvest, and management relevant metrics for all 2.6 million stream catchments and watersheds across the conterminous U.S. These data points in StreamCat can assist users in developing watershed-specific nutrient management plans. We present uses of these data for assessing surface and groundwater areas and discuss possible future research.   The presentation is part of the upcoming seminar July 2, 2025: Applying EPA’s National Nutrient Inventory to quantify landscape nutrient inputs and interception to support state and local water quality objectives.   Harmful Algal Blooms, Hypoxia, and Nutrients Research Webinar Series | US EPA

Impact/Purpose

The National Nutrient Inventory presents a compilation of datasets quantifying N and P inputs, outputs, and management relevant metrics across the conterminous US, available at HUC12 and county scales. We used these data to provide downscaled NHDPlus catchment and accumulated watershed nutrient metrics across the conterminous US from 1987-2017. These data present the highest resolution nutrient data available across the conterminous US and will be readily accessible through StreamCat’s Application Programming Interface and visualized through StreamCatTools. We will present case studies on using these data for surface and groundwater impaired areas of interest. Additionally, these refined data can be used to calibrate predictive models for assessing the impact of nutrient inputs and outputs on surface and groundwater and and run time series analyses on nutrient mass balances at management-relevant scales. These data can be used by a wide variety of stakeholders to support nutrient management goals. This presentation supports research being conducted under SSWR.405.1.1.4 (Quantification of nutrient inputs to conterminous US stream and lake watersheds via accumulation of nutrient inventories in StreamCat and LakeCat) and SSWR.402.2.3.4 (Expanding the use and usability of StreamCat and LakeCat watershed characterization for NARS and other EPA programs and partners).

Citation

Markley, S. Quantifying 30 Years of spatially explicit catchment and watershed nutrient budgets through the NNI in StreamCat. Harmful Algal Blooms, Hypoxia, and Nutrients Research Webinar Series, Corvallis (online), OR, July 02, 2025.