The U.S. Geological Survey (USGS) is developing SPARROW models (SPAtially Related Regressions On Watershed Attributes) to assess the transport of contaminants (e.g., nutrients) through the Pacific drainages of the United States (the Columbia River basin; the coastal drainages of Washington, Oregon, and California; the Klamath River basin; the Central Valley of California, and the west slopes of the Sierra Nevada Mountains). SPARROW relates instream water quality measurements to spatially referenced characteristics of watersheds, including contaminant sources and the factors influencing terrestrial and aquatic transport. Livestock manure used as fertilizer on farmland is a potential source of nutrients delivered to streams. These data sets represent an estimate of the amount of manure nitrogen and phosphorus generated at cattle animal feeding operations (AFO''s, such as dairies and feedlots) in 2012 that was applied to farmland. The data sets were created by estimating the total amount of manure nutrients generated at each AFO in 2012, the amount from that total that was retained and applied to farmland immediately surrounding each AFO, and the amount that was exported for application to farmland within the counties in which those AFO's were located. The application to farmland was estimated by either 1) disaggregating the retained manure nutrients to the pasture and cultivated land around each AFO based on the number of cattle housed there in 2012 or 2) disaggregating the exported manure nutrients to the pasture and cultivated land within the counties in which those AFO's were located.
