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. Cattle manure applied to grazing land is a potential source of nutrients delivered to streams. The spatial data set “Application of manure nitrogen generated by cattle housed in animal feeding operations to county-wide farmland within the Pacific drainages of the United States (2012)” represents an estimate of the amount of cattle manure nitrogen generated at animal feeding operations (such as dairies and feedlots) in 2012 that was applied to farmland within the counties in which those facilities were located. This data set was created by estimating the total amount of manure nitrogen that was exported to market in 2012 within each county and disaggregating that amount to the farmland within that county.