Leakage of water from public supply distribution networks is responsible for significant phosphorus fluxes within many urban catchments across the United States

The release of phosphorus into aquatic environments as a result of anthropogenic activity has led to eutrophication of many fresh and coastal waters around the globe and across the United States (US). Dosing of public water supplies (PWS) with phosphate (PO₄) compounds is undertaken around the globe, including many parts of the US, in order to inhibit corrosion and release of lead and copper within water distribution network pipes. However, 17% of this treated water is released into the environment due to leakage, resulting in previously unquantified fluxes of phosphorus into the environment. We have calculated this PWS leakage PO₄ flux (as phosphorus; PO₄-P) for the US to be between 2.2-6.7 kt PO₄-P yr^-1. County PWS leakage fluxes range from 0-2,865 kg PO₄-P km^-2 yr^-1, and the relative magnitude of the fluxes in many urban counties across the northeastern US highlights the need for these previously unquantified fluxes to be incorporated into catchment nutrient balances. Not only do PWS leakage fluxes of PO₄-P make a potentially significant contribution to eutrophication in urban catchments, but they also represent a loss of phosphorus that subsequently cannot be easily recovered at wastewater treatment plants, driving increased extraction of non-renewable and dwindling global phosphorus rock reserves.