Direct and indirect hydrological controls on E. coli concentration and loading in midwestern streams

Area of Science:

• Environmental Science
• Hydrology
• Microbiology

Background:

• Agricultural watersheds are significant sources of microbial contamination.
• Understanding hydrological controls on E. coli is crucial for water quality management.

Purpose of the Study:

• To investigate hydrological factors influencing E. coli concentration and loading in artificially drained agricultural watersheds.
• To identify key indicators for predicting E. coli contamination.

Main Methods:

• Analysis of E. coli concentration and loading data from two agricultural watersheds.
• Correlation analysis between E. coli and hydrological variables (discharge, precipitation, antecedent precipitation, turbidity, temperature).
• Comparison of findings across different flow conditions (base flow vs. high flow) and seasons.

Main Results:

• E. coli concentrations were lower at base flow, but loads were higher at high flow.
• E. coli loads were significantly higher in winter/spring than in summer/fall.
• Discharge and precipitation were key indicators of E. coli concentration, while 7-day antecedent precipitation (7dP) indicated loading.
• Turbidity and 7dP were strong predictors at base flow, with spatial variations observed.

Conclusions:

• Hydrological factors, particularly discharge, precipitation, 7dP, and turbidity, play a significant role in E. coli dynamics in agricultural watersheds.
• Turbidity and 7dP show potential for identifying E. coli hotspots during base flow in artificially drained Midwest landscapes.
• Seasonal variations impact E. coli loading, with higher loads in winter/spring.