Agricultural activities alter watershed functions and increase nutrient concentrations in streams and lakes through excess fertilizer use and altered flow paths. To mitigate these impacts while maximizing farmer profits, various agricultural management practices are recommended and implemented. However, the complex interactions among climate, crop, soil, and market incentives make it challenging to accurately predict how farmer decisions affect watershed responses, such as stream water quality and crop yield.

This study employs the Soil and Water Assessment Tool (SWAT) to enhance our understanding of the interactions between agricultural management decisions and watershed functions in the Portage River Basin, part of the Western Lake Erie Basin. We hypothesize that the impact of agricultural management practices can vary with climate and soil conditions. To test this, we generated a suite of management scenarios based on historical data, including crop choice/rotation strategies, planting and harvesting dates, and fertilizer application timing and amounts. We evaluated nutrient exports, crop yields, and farmer profits at both field and watershed scales.

Our findings identify which agricultural management practices can sustain economic viability while minimizing negative impacts on stream water quality, and where these practices are most effective. Additionally, this work provides benchmark datasets for developing a coupled agent-based model (ABM) integrated with the watershed model, enhancing our capacity to simulate key processes and interactions among human, agricultural, and watershed systems.