Editing Phosphorus Load Flux to Water (section)

== Boundary Conditions ==
Boundary inclusions encompass all phosphorus inputs to surface waters within the geographic unit of analysis, including diffuse sources such as agricultural runoff and atmospheric deposition, as well as point sources like sewage effluent. Exclusions include phosphorus retained or transformed within soils and sediments prior to reaching the water body, phosphorus inputs to groundwater not connected to surface waters, and internal phosphorus cycling within aquatic systems. The spatial boundaries correspond to watershed or catchment areas, ensuring that flux measurements reflect inputs entering the aquatic environment rather than phosphorus already present or recycled internally.