Escherichia coli concentrations in waters of a reservoir system impacted by cattle and migratory waterfowl

Authors: HANSEN, SAMUEL - University Of Nebraska; MESSER, TIFFANY - University Of Nebraska; MITTELSTET, AARON - University Of Nebraska; Berry, Elaine; BARTELT-HUNT, SHANNON - University Of Nebraska; ABIMBOLA, OLUFEMI - University Of Nebraska

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2019
Publication Date: 2/1/2020
Citation: Hansen, S., Messer, T., Mittelstet, A., Berry, E.D., Bartelt-Hunt, S., Abimbola, O. 2020. Escherichia coli concentrations in waters of a reservoir system impacted by cattle and migratory waterfowl. Science of the Total Environment. 705:135607. https://doi.org/10.1016/j.scitotenv.2019.135607.
DOI: https://doi.org/10.1016/j.scitotenv.2019.135607

Interpretive Summary: Surface water contaminated with feces is a source of pathogens that can cause water- or foodborne illness when the water is used for irrigation, recreation, or for drinking water. Identifying the sources of fecal contamination and understanding the factors that affect pathogen prevalence and concentration are critical first steps to applying effective water management practices to reduce contamination risk. In this work, concentrations of nonpathogenic Escherichia coli were used as indicators of the extent of fecal contamination of water in a stream flowing through a cattle grazing area. Waterfowl are common in the stream, which is located in the Nebraska region of the Central Flyway for avian migration. E. coli concentrations were measured in water samples collected during five rainstorms occurring during the summer and fall. Cattle density had a significant effect on E. coli concentrations during the summer season, while waterfowl density had a significant effect on E. coli concentrations during the fall. In addition, the probabilities of E. coli concentrations exceeding the Environmental Protection Agency fresh water criteria increased as the water moved downstream, which demonstrates how upstream contamination can impact water quality in downstream locations. These findings demonstrate the need for management practices to limit the entry of E. coli in storm runoff into streams in pastured areas, as well as the need for microbial testing of surface water before use to irrigate human food crops.

Technical Abstract: Recent pathogenic Escherichia coli contamination of fresh vegetables that originated from irrigation water has increased awareness and importance of identifying sources of E. coli entering these agroecosystems. However, inadequate methods for accurately predicting E. coli occurrence and sources in waterways continue to limit the identification of appropriate and effective prevention and treatment practices. Therefore, the primary objectives of this study were to: (1) Determine the concentration of E. coli during storm events in a hydrologic controlled stream situated in a livestock research operation that is located in the Central Flyway for avian migration in the United Sates, Great Plains; and (2) identify trends between E. coli concentrations, grazing rotations, and avian migration patterns. The study sampled five rainfall events (three summer and two fall) to measure E. coli concentrations throughout storm events. A combination of cattle density and waterfowl migration patterns were found to significantly impact E. coli concentrations in stream. Cattle density had a significant impact during the summer season (p<.0001), while waterfowl density had a significant impact on E. coli concentrations during the fall (p = 0.0422). The downstream reservoir had exceedance probabilities above the Environmental Protecion Agency freshwater criteria >85% of the growing season following rainfall events. Based on these findings, implementation of best management practices for reducing E. coli concentrations during the growing season and testing of irrigation water prior to application are recommended.