Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2004
Publication Date: 7/28/2004
Citation: Moorman, T.B., Tomer, M.D., Douglass, E.A., Greenan, C.M. 2004. Movement and survival of fecal contaminant indicators in an Iowa watershed. Soil and Water Conservation Society. Available:www.swcs.org.
Technical Abstract: The South Fork of the Iowa River drains a 78,000 ha (215,000 ac) watershed in north-central Iowa. The land is about 85% in row-crop (corn-soybean) agriculture. There are approximately 95 confined feeding operations (mostly swine), and in lower stream reaches there are wildlife, pastures with cattle access to streams, and homes that may have inadequate on-site waste treatment. These may all be sources for fecal contamination of streams. Since August 2001, stream water monitoring has been conducted to evaluate the occurrence of Escherichia coli in the South Fork watershed. During 2002, monitoring was expanded to include tile-drain discharge, soil populations following application of manure, and event-based monitoring of field runoff and stream flow. The first 12 months of stream monitoring showed E. coli populations exceeded a recreational-contact standard of 200 mpn/100 mL between 34 and 56% of the time, depending on the sub-basin. Tipton Creek showed a downstream increase in E. coli populations, i.e., with increasing distance from most swine feeding operations. This indicates downstream sources may be important, or there are resident populations in stream sediments that are released during runoff events. E. coli populations vary seasonally, and correlations with temperature, and sediment and nutrient concentrations were observed. Soil monitoring showed E. coli populations declined about 90% per week after fall manure application. But a runoff event shortly after application showed a large pulse of E. coli in field runoff and in streams. Research to better understand the sources and risks of fecal contamination in this watershed is continuing.