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

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 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 States. 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 the 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 = .0422). The downstream reservoir had exceedance probabilities above the Environmental Protection 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.