National Water-Quality Assessment (NAWQA) Project
<-- BACK TO: Changes in Nutrient and Sediment Concentrations in Streams and Rivers of the United States, 1993-2003
Increases in nitrogen concentrations, adjusted for streamflow, occurred from 1993 to 2003 in 21 percent of the streams, and decreases were estimated in 16 percent of the 137 streams assessed. Flow adjusted nitrogen concentrations increased by more 50 percent in 7 percent of the streams. Nitrogen 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, population, and atmospheric deposition.