A Systems Approach to Modeling Watershed Ecohydrology and Pesticide Transport

Area of Science:

• Agricultural hydrology
• Environmental modeling
• Ecosystem protection

Background:

• Nonpoint-source pollution from agriculture impacts surface water quality.
• Agricultural practices raise concerns regarding Endangered Species Act (ESA) compliance, especially for Pacific Northwest salmonids.
• Understanding pollutant transport is crucial for ecological risk assessment.

Purpose of the Study:

• To characterize ecohydrology and solute transport in the Zollner Creek watershed using the Soil and Water Assessment Tool (SWAT).
• To evaluate model parameterization scenarios for simulating watershed ecohydrology and solute transport.
• To assess the model's ability to predict pesticide concentrations in surface water.

Main Methods:

• Utilized the Soil and Water Assessment Tool (SWAT) for watershed modeling.
• Integrated institutional expertise with local knowledge for model parameterization.
• Employed probabilistic methods to simulate pesticide application patterns.
• Correlated SWAT-simulated atrazine concentrations with observed data.

Main Results:

• The SWAT model successfully simulated general trends of atrazine surface water concentrations.
• A correlation ( = 0.37) was found between simulated and observed atrazine concentrations.
• The model provided concurrent mean estimates of daily atrazine surface water concentrations.

Conclusions:

• The developed SWAT model application can characterize watershed-scale ecohydrology and pesticide transport.
• Further model development can enhance understanding of continuous pesticide loading and environmental impacts.
• This approach facilitates the assessment of refined mitigation strategies for agricultural nonpoint-source pollution.