Bacterial accumulation dynamics in runoff from extreme precipitation.

Area of Science:

• Environmental Science
• Microbiology
• Water Quality Management

Background:

• Extreme precipitation events are increasing globally, posing risks to surface water quality.
• The quantity and impact of bacteria transported by rainfall runoff are not fully understood.
• Understanding bacterial runoff is crucial for predicting microbial contamination of water sources.

Purpose of the Study:

• To quantify bacterial concentrations in runoff from different land surfaces under simulated rainfall.
• To develop cumulative dynamic models for estimating bacterial loads entering water bodies.
• To assess the influence of rainfall characteristics and land cover on bacterial transport.

Main Methods:

• Simulated 30 rainfall scenarios with intensities from 19.3 to 250 mm/h.
• Measured instantaneous concentrations of culturable (R2A, NA) and viable bacteria in runoff.
• Developed cumulative dynamic models based on measured bacterial concentrations.

Main Results:

• Bacterial concentrations in runoff varied significantly by land surface type (forest, grassland, bare soil).
• Estimated maximum bacterial loads entering water sources ranged from 10^9.38-11.31 CFU/m^2 (culturable) and 10^11.84-13.25 cells/m^2 (viable).
• Rainfall characteristics influenced model fitting and bacterial accumulation dynamics (p < 0.01).

Conclusions:

• Forest and grassland runoff present a high microbial risk, persisting even during "Drought-to-Deluge Transition" periods.
• Bacterial accumulation models offer valuable predictive tools for microbial risks during precipitation events.
• Findings support ensuring drinking water safety amidst climate change challenges.