Linking watershed modeling and bacterial source tracking to better assess E. coli sources

Area of Science:

• Environmental Science
• Water Quality Management
• Microbial Ecology

Background:

• Terrestrial E. coli contamination is complex, influenced by urbanization and grazing.
• Accurate assessment of bacterial sources, especially wildlife, is lacking.
• Reducing E. coli in impaired water bodies requires understanding and managing contamination sources.

Purpose of the Study:

• To identify critical E. coli sources in the Arroyo Colorado watershed.
• To evaluate the effectiveness of conservation practices in mitigating E. coli.
• To improve bacterial source tracking within a modeling framework.

Main Methods:

• Utilized a process-based hydrologic and water quality model.
• Integrated bacterial source tracking (BST) data for wildlife and human contributions.
• Incorporated GIS, census data, and expert knowledge to identify E. coli sources.

Main Results:

• Enhanced E. coli source data significantly improved model accuracy (R²=0.90 vs. 0.59).
• Wildlife contributions remain a significant E. coli source, particularly in agricultural and range lands.
• Combined nonpoint source management, advanced wastewater treatment, and aeration effectively restored water uses.

Conclusions:

• Accurate source identification is key to effective E. coli mitigation.
• Wildlife is a persistent E. coli contributor, necessitating targeted management.
• Integrated strategies including source control and in-stream measures are vital for water quality restoration.