Source specific fecal bacteria modeling using soil and water assessment tool model

Area of Science:

• Environmental Science
• Water Quality Modeling
• Microbial Ecology

Background:

• Fecal bacteria contamination poses significant risks to water safety and public health.
• Accurate identification of fecal bacteria sources, including livestock, human, and wildlife, is crucial for effective water management.
• Bacteria source tracking (BST) methods are essential for pinpointing non-point sources of contamination.

Purpose of the Study:

• To evaluate source-specific fecal bacteria using the Soil and Water Assessment Tool (SWAT) microbial sub-model.
• To model fecal bacteria from livestock, human, and wildlife sources individually and in combination.
• To assess the model's performance in predicting flow, sediment, nutrients, and bacteria concentrations.

Main Methods:

• Utilized the SWAT microbial sub-model 2005 with three years of observed BST data (2004-2006).
• Calibrated and validated the SWAT model for flow, sediment, and total fecal coliform bacteria (FCB) at multiple sub-watersheds.
• Modeled source-specific FCB concentrations from combined and individual sources (livestock, human, wildlife).

Main Results:

• The SWAT model demonstrated good to very good agreement for daily flow (R(2) 0.52-0.84) and sediment (R(2) 0.50-0.87).
• Model performance for nutrients and total fecal bacteria showed variable agreement, ranging from unsatisfactory to very good.
• Agreement decreased for single bacteria sources (R(2) -5.03 to 0.39), indicating potential BST uncertainty and spatial variability.

Conclusions:

• The SWAT model can predict watershed hydrology and sediment transport effectively.
• Modeling source-specific fecal bacteria presents challenges due to BST data uncertainty and spatial variability.
• This research advances bacteria modeling knowledge and highlights the complexities of source attribution in water quality studies.