HR: 17:15h
AN: H54D-06    [Abstracts]
TI: Water Quality Signal of Animal Agriculture at USGS Monitoring Stations is Related to Animal Confinement and/or Farm Size
AU: * Smith, R A
EM: rsmith1@usgs.gov
AF: US Geological Survey, MS413 National Center, Reston, VA 20192, United States
AU: Alexander, R B
EM: ralex@usgs.gov
AF: US Geological Survey, MS413 National Center, Reston, VA 20192, United States
AU: Schwarz, G E
EM: gschwarz@usgs.gov
AF: US Geological Survey, MS413 National Center, Reston, VA 20192, United States
AB: US animal agriculture has undergone major structural changes over the past two decades, with the total number of livestock producers declining dramatically and the average size of the remaining operations increasing substantially. The result has been a pronounced trend towards greater spatial concentration and confinement of livestock. The change raises important questions about the water quality effects of animal agriculture in regions where livestock waste production has become more intensive but recovery, handling, and application of animal wastes to cropland more systematized. In previous research, we developed three separate national-level SPARROW models of surface water contaminants (total nitrogen, total phosphorus, and fecal coliform bacteria). Based on USGS monitoring and ancillary data from more than 400 US stream and river basins, the models include point and nonpoint sources of contaminants, land-to-water transport factors, and in-stream loss processes; parameter estimation is by non-linear regression. In this study we report on a pattern in the statistical results for the three models: The source coefficients (quantity of contaminant delivered to streams per unit of contaminant input) for unconfined animals are consistently larger and more statistically significant than those for confined animals. The implicit meaning is that something associated with waste management on large farms and/or animal confinement (e.g. retention period, recovery of manure for application to crops and subsequent crop uptake, and/or better waste treatment) reduces the average water quality signal of this scale of animal agriculture (per unit of manure input) to barely detectable at downstream monitoring stations, while the water quality signal from unconfined animal agriculture is more clear. The county-level data for confined and unconfined manure inputs (defined primarily by farm size) are from the USDA, and are spatially distributed in the model GIS by 1-km land use data. To date, our analytical probing of the results has not identified a viable alternative to the implicit conclusion.
UR: http://water.usgs.gov/nawqa/sparrow/
DE: 0402 Agricultural systems
DE: 0466 Modeling
DE: 1847 Modeling
DE: 1848 Monitoring networks
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting