Many conservation practices and implementation programs exist to address nonpoint source (NPS) pollution losses from agricultural landscapes (Helmers et al., this issue). In order to select the most appropriate practices and programs for reducing NPS pollution in a specific region while maintaining economic return for the landowner, the interacting processes of agricultural management and watershed hydrology need to be understood across broad spatial scales. On a nationwide basis, it is easy to see how NPS pollution in one part of the country might be different than those in another region of the country. For example, cotton growers in the South, dairy farmers in the Northeast, cattle ranchers in the West, and grain farmers in the Midwest all face unique challenges based on differences in climate, soil types, and cropping patterns. Each region relies on a different set of conservation practices and programs to address NPS pollution. To be effective, conservation systems must be based on an understanding of specific management impacts on water quality problems, and therefore be targeted to reduce, intercept, and/or treat contaminants moving via surface or sub-surface pathways from working agricultural lands.