Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 13, 2006
Publication Date: October 13, 2006
Citation: Moorman, T.B., Tomer, M.D., James, D.E. 2006. Escherichia coli and enterococcus in the south fork of the Iowa river watershed [abstract]. Soil and Water Conservation Society. p. 87.
Confined swine production has increased in Iowa over the last decade and there is uncertainty about the impact of these operations on water quality. We have monitored the populations of Escherichia coli and Enterococcus in the 78,000 ha South Fork of the Iowa River watershed from 2003 through 2005 to understand spatial and temporal trends. Sampling contrasted two sub-basins that have high populations of swine, Tipton Creek and the South Fork, against Beaver Creek which has lower swine populations. Individual runoff events from manured lands produced large populations of E. coli and Enterococcus, but long-term average bacterial populations in the sub-basins did not correspond to the swine populations of the sub-basins. Runoff from field-scale catchments with and without manure suggests that wildlife also contribute to stream water populations. These bacterial populations showed temporal trends with peak populations in late summer. Variability in E. coli populations was best described by a model that included temperature and the percentage of storm flow contributing to discharge. Monitoring subsurface drainage systems for these bacteria shows lower populations than in stream water, but some storm events increase bacterial transport. The impact of cropping patterns and conservation practices will be discussed.