Watershed characterization involves determining the attributes or characteristics of the watershed, such as topography, soil types, land use/land cover, impervious area, waterbody types, nutrient loads, nutrient sources, and stakeholder interest and willingness to participate. In addition to current conditions, past and projected conditions of the watershed should also be characterized. Past conditions can indicate areas where legacy nutrient sources might be expected, or can be used to develop reduction targets. Management activities designed based on past or current conditions can be rendered ineffective by future land use/land cover changes in the watershed. Considering projected changes in land use/land cover and population can better ensure management success.

Prioritizing areas for nutrient-related restoration and protection activities is also part of watershed characterization.