The purpose of this work is to introduce SWAT (Soil and Water Assessment Tool) model, EPIC (Erosion Productivity-Impact Calculator) model and a dynamic economic optimization model as tools to estimate cost of water pollution abatement. Beaty creek watershed in Delaware County, Oklahoma was chosen as a case study to apply these tools. Objective of this study is to estimate the marginal abatement costs for poultry farmers if they were to reduce poultry litter application for water improvement in a watershed. The study successfully derived the marginal abatement costs for different sub-basins. These pointed out the areas where non-point source pollution can be reduced at least cost. These areas were not easily identified by visual examination of the data. This result allows the regulatory agency to focus its effort to these areas and thus, be able to reduce its administrative and enforcement costs.