E. coli in PA streams as affected by climate forcing

Abstract. Each year, more than 9 million foodborne illnesses are estimated to be caused by major pathogens. More than 70% of the cropland for vegetables is irrigation water may contain pathogens or potential bacteria that affect human health. The FDA (Food and Drug Administration) mandated the Food Safety Modernization Act in 2011 and it includes a regulation for irrigation water based on E. coli concentration, however there is no regulation for how or when to collect the samples. To find the optimal monitoring guidelines, it is necessary to discover, evaluate and integrate the knowledge affecting microbial quality of irrigation water using watershed model. In this study, the modified SWAT (Soil and Water Assessment Tool) model was applied for E. coli concentration on the stream in the Little Cove Creek Watershed in Pennsylvania with forestry and dairy pasture land use using the 90-year meteorological data since 1923. The geometric mean of daily simulation results for 90 years during growing periods is estimated 141 CFU of E. coli in 100ml water with excess rate of FDA regulation is about 59%. In addition, stream flow water samples from the simulation were collected 20 times per year and iterated 100 times per year. The geometric mean of samples is expected 153 CFU of E. coli in 100 ml with the 82% excess rate of regulation. Further developments to find the mechanisms under base flow and apply these mechanisms are necessary for better simulation of bacteria transport for irrigation sources. This study will utilize as the basic tools for better expectation and to support the guideline for optimal monitoring for food safety.