HR: 1340h
AN: H43B-0371    [Abstracts]
TI: Effects of Structural Changes in US Animal Agriculture on Fecal Bacterial Contamination of Streams: Comparison of Confined and Unconfined Livestock Operations
AU: * Smith, R A
EM: rsmith1@usgs.gov
AF: U S Geological survey, MS 413, Reston, VA 20192 United States
AU: Alexander, R B
EM: ralex@usgs.gov
AF: U S Geological survey, MS 413, Reston, VA 20192 United States
AU: Schwarz, G E
EM: gschwarz@usgs.gov
AF: U S Geological survey, MS 413, Reston, VA 20192 United States
AB: US animal agriculture has undergone major structural changes over the past two decades. Although the total size of the national livestock population (when measured in animal units) has remained relatively unchanged over the period, the number of livestock producers has declined dramatically, and the average size of the remaining operations has increased substantially. A related change has been a pronounced trend towards greater confinement and spatial concentration of farm animals. These changes raise important questions about the water quality effects of animal agriculture. Fewer, larger operations and increased animal confinement might be expected to spatially focus the discharge of manure-related contaminants and result in a smaller number of more heavily impacted watersheds in high production areas. But at a less simplistic level, assessing the overall national effects of the restructuring of animal agriculture requires a spatially detailed analysis covering a wide range of watershed scales. In this study, we use an empirical (SPARROW) model of fluvial fecal coliform bacteria loads to compare the effects of confined and unconfined farm animal populations on levels of fecal contamination in US streams and rivers. The model was calibrated with monitoring data from 341 stream and river monitoring stations distributed among the nation's 48 conterminous states. Bacteria monitoring records cover the period 1978 to 1995. The model accounts for six categories of fecal coliform sources: municipal point sources, urban runoff, forest land, shrublands/wetlands, confined animal agriculture, and unconfined animal agriculture. Bacterial inputs from agricultural sources for the study period are based on data from the Agricultural Statistics Service and the Natural Resources Conservation Service. Model output (fecal coliform loads and concentrations) is produced for 62,000 stream locations.
DE: 1803 Anthropogenic effects
DE: 1871 Surface water quality
DE: 0400 Biogeosciences
DE: 0840 Evaluation and assessment
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting