Fecal indicator sources in small creeks

Authors: Coppock, Cary; HONG, EUNMI - Orise Fellow; Pachepsky, Yakov; HARRIGER, DANA - Warren Wilson College; LYBARBER, VANESSA - Warren Wilson College; Shelton, Daniel

Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Fecal indicator organisms (FIO) in surface water have been widely adopted as surrogates for human gastro-intestinal pathogens, despite available data indicating that the correlations are quite low. Nonetheless, high levels of FIO are a source of concern for agricultural, recreational and industrial users. High concentrations of fecal indicator organisms (FIO) are commonly found in post-storm elevated flow of low order creeks (headwater tributaries) and high order creeks (downstream). Predicting and identifying these hazards has become a priority for food safety professionals. Recent work raises questions about whether entrained bacteria are attached to perturbed sediments and whether they arrive mostly as runoff from adjacent land. Whence do they come? With enactment of the Food Safety Modernization Act (FSMA, 2011), (FSMA Produce Rule, 2015) and burgeoning state and local laws, produce irrigation water is expected to remain below threshold FIO concentrations. Ongoing research suggests that FIO inputs between storm events correlate to geography and environmental factors other than storm runoff. The objective of our monitoring studies is to model spatial and temporal dimensions of FIO plumes and describe FIO sources impacting irrigation water. Five sites were selected to monitor FIO on a low to mid-order creek in south central Pennsylvania. Weekly water grab samples were collected for 65 weeks including two summers and evaluated for Escherichia coli and Enterococcus. Microbial concentrations were compared to creek flow (volume x velocity) to extrapolate microbial loads with a focus on base flow microbial concentrations. Results suggest that some irrigation sources may receive FIO inputs perpetually. We also have identified gaps in effectiveness of predicting threats to irrigation water using classic parameters at available spatial and temporal resolutions. These knowledge gaps (sediment attachment and resolution of environmental data) may affect a discord between FSMA Produce Rule compliance, and reliable prediction of actual food safety threats.