Subsurface Transport of Orthophosphate in Five Agricultural Watersheds

A recently published USGS study, “Subsurface Transport of Orthophosphate in Five Agricultural Watersheds, USA”, highlights some of the factors that contribute to movement of phosphate in ground water and the potential impact on levels in streams.  The study looked at 5 agricultural watersheds from California to Maryland.  Key findings include the following:

  • Phosphorus subsurface movement was controlled by sorption onto iron oxides or clays.
  • Water chemistry and soil types affected phosphorus transport to the aquifers.
  • Low pH conditions within an aquifer in Maryland prevented phosphorus transport.
  • Geochemical modeling was used to assess adsorption.

An abstract of the report and access to the complete study is available at