Preprint #96-3
Spatio-Temporal Statistical Modeling of
Livestock Waste in Streams
by
Noel Cressie and James J. Majure
Abstract
Livestock agriculture (e.g., dairy, beef, pork, poultry) in the USA is
tending rapidly toward operations where a large number of animals are
concentrated in a relatively small area. The economies of scale are
counterbalanced by the dangers of pollution from inadequate treatment
of animal waste. Traditional methods of treatment involve lagoon
retention and subsequent spreading on fields but the sheer volume of
production seems to be outstripping these and other technologies.
Surface-water runoff finds its way into streams and rivers, ultimately
polluting all downstream segments of the watershed. The topic of this
paper is spatio-temporal statistical modeling of (log) nitrate
concentration in the upper North Bosque watershed, which is a region of
concentrated dairy operations. A model is fitted from daily data
collected over a period of 15 months, at 17 stream monitoring sites
throughout the watershed. Optimal predictions of unknown nitrate
concentration, at all stream locations at any given time, are obtained,
along with a measure of their variability. The model allows for policy
changes to be made, and assessed, based on the consequent spatio-temporal
predictions.
Copies of preprints are available from the author upon request. Use
the preprint number (located at the top of the page) and
make the request directly to the author, Iowa State
University,
Department of Statistics, Snedecor Hall, Ames, IA 50011-1210.