Trends in total phosphorus concentrations, 1993-2003

Increases in phosphorus concentrations, adjusted for streamflow, occurred from 1993 to 2003 in 33 percent of the streams, and decreases were estimated in 16 percent of the 171 streams assessed. Flow adjusted phosphorus concentrations increased by more 50 percent in 26 percent of the streams assessed. Phosphorus concentrations were adjusted for streamflow so that changes in nutrient concentrations could be evaluated in comparison to changes in nutrient sources, such as fertilizer application, animal manure, wastewater discharges, and population. More information about changes in nutrients and sediment concentrations in streams, 1993-2003, is available in the USGS archive.