Explaining differential sources of zoonotic pathogens in intensively-farmed catchments using kinematic waves

Area of Science:

• Environmental Science
• Microbiology
• Hydrology

Background:

• Bacterial contamination in streams during flood events poses risks to water users.
• Escherichia coli (E. coli) is often used as an indicator for health risks, but its concentration patterns may differ from actual pathogens like Campylobacter.
• Observed discrepancies in peak concentrations between E. coli and Campylobacter during floods suggest multiple potential sources.

Purpose of the Study:

• To investigate the differential time-concentration patterns of E. coli and Campylobacter during flood events in agricultural catchments.
• To develop a theoretical framework explaining these patterns based on pathogen source and transport mechanisms.
• To inform public policy and risk assessment for downstream water users.

Main Methods:

• Field surveys of stream water quality during flood events.
• Analysis of time-concentration data for E. coli and Campylobacter relative to flood hydrographs.
• Development of a theoretical model based on kinematic wave theory to simulate contaminant transport from different sources.

Main Results:

• E. coli peak concentrations can lead, coincide with, or lag behind flood peaks, while Campylobacter peaks often coincide with flood peaks.
• The developed kinematic wave theory model successfully explains these observed differential time-concentration patterns.
• The model identifies three predominant pathogen sources: sediment entrainment, local land runoff, and upstream releases.

Conclusions:

• The timing of indicator bacteria (E. coli) and pathogen (Campylobacter) peaks during floods provides crucial information about their sources.
• Identifying predominant pathogen sources through these patterns is essential for targeted management strategies.
• This research improves quantitative health risk assessments for recreational, drinking water, and food production uses of water bodies.