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Regional nutrient trends in streams and rivers of the United States, 1993-2003

January 1, 2009

Trends in flow-adjusted concentrations (indicators of anthropogenic changes) and observed concentrations (indicators of natural and anthropogenic changes) of total phosphorus and total nitrogen from 1993 to 2003 were evaluated in the eastern, central, and western United States by adapting the Regional Kendall trend test to account for seasonality and spatial correlation. The only significant regional trend was an increase in flow-adjusted concentrations of total phosphorus in the central United States, which corresponded to increases in phosphorus inputs from fertilizer in the region, particularly west of the Mississippi River. A similar upward regional trend in observed total phosphorus concentrations in the central United States was not found, likely because precipitation and runoff decreased during drought conditions in the region, offsetting the increased source loading on the land surface. A greater number of regional trends would have been significant if spatial correlation had been disregarded, indicating the importance of spatial correlation modifications in regional trend assessments when sites are not spatially independent.

Citation Information

Publication Year 2009
Title Regional nutrient trends in streams and rivers of the United States, 1993-2003
DOI 10.1021/es803664x
Authors Lori A. Sprague, David L. Lorenz
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Series Number
Index ID 70035134
Record Source USGS Publications Warehouse
USGS Organization Colorado Water Science Center

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