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Quantification of nutrient inputs to conterminous US stream and lake watersheds via accumulation of nutrient inventories in StreamCat and LakeCat
Citation:
Markley, S., M. Weber, M. Brehob, M. Pennino, T. Hudson, R. Hill, S. Alford, J. Compton, AND R. Sabo. Quantification of nutrient inputs to conterminous US stream and lake watersheds via accumulation of nutrient inventories in StreamCat and LakeCat. U.S. Environmental Protection Agency, Washington, DC, 2025.
Impact/Purpose:
Quantifying watershed nutrients are crucial components of state-led efforts to improve nutrient reduction strategies. However, assembling these data at scales that are relevant to management, such as local stream catchments or watersheds. This subproduct provides downscaled data from EPA's National Nutrient Inventory (NNI; https://www.epa.gov/water-research/national-nutrient-inventory-portfolio) for 2.64 million local stream catchments and full accumulative watersheds across the conterminous US. With the incorporation of NNI into StreamCat, we generated over 3.5 billion pieces of data, comprising three decades of nutrient estimates, resulting in a novel and robust resource to explore nutrient inputs. 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 watershed planning to meet statutory requirements under the Clean Water Act. The data are available via EPA's StreamCat online database, API, and R package (StreamCatTools). The submission of this subproduct is in partial fulfillment of SSWR405.1.1.4, Quantification of nutrient inputs to conterminous US stream and lake watersheds via accumulation of nutrient inventories in StreamCat and LakeCat. Accumulation of the NNI in LakeCat is forthcoming.
Description:
Publication of EPA’s Nutrient Inventory is a critical step towards thorough mapping and accounting of sources of N and P to US landscapes. However, summaries of nutrients within accumulative watersheds are needed to develop accurate watershed-level nutrient budgets and relate landscape inputs to instream nutrient concentrations. This subproduct will accumulate the Nutrient Inventory across available years for all streams and lakes within the medium resolution National Hydrography Dataset Plus version 2 (NHDPlus), i.e., 2.6 million stream segments and nearly 400,000 lakes across the conterminous US. These data will allow OW to easily and rapidly identify the dominant sources of N or P for any stream segment or lake in the US. Further, these data will be made accessible through the EPA’s StreamCat and LakeCat datasets and a soon-to-be released online database and an application programming interface (API). This database and API will make nutrient watershed accumulations readily accessible and easily integrated by a variety of OW programs and tools. Finally, the accumulated nutrient data will serve as the basis for a multiple proposed StRAP subproducts and models in SSWR.401, SSWR.404, and SSWR.405. These data will contribute directly to OW, region, and state efforts to identify and reduce non-point nutrient sources. Having spatially explicit data about nutrient sources and loads can help target and inform restoration and conservation efforts, as well as more formal TMDLs, nutrient reduction plans, and groundwater management approaches. This subproduct will produce a database of accumulated nutrient values for at least 2.6 million stream segments and 400,000 lakes of the medium resolution National Hydrography Dataset Plus version 2 (NHDPlus). These data will be made accessible through the StreamCat and LakeCat datasets. They will also be made available as an online database with application programming interface (API) that will facilitate data acquisition and use by OW and state partners. This database will provide a state-of-the science accounting of nutrient sources that drain to all streams and lakes in the conterminous US. It will allow EPA and state partners to identify dominant sources of N and P to individual waterbodies and will greatly facilitate nutrient reduction strategies and planning.