EPA Science Inventory

Spatial and Temporal Patterns of Dissolved Nitrogen and Phosphorus in Surface Waters of a Multi-Land Use Basin

Citation:

Evans, D., S. Schoenholtz, J. Wigington, S. Griffith, AND W. Floyd. Spatial and Temporal Patterns of Dissolved Nitrogen and Phosphorus in Surface Waters of a Multi-Land Use Basin. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 186(2):873-887, (2014).

Description:

Research on relationships between dissolved nutrients and land use at the watershed scale is a high priority for protecting surface water quality. We measured dissolved nitrogen (DN) and ortho-phosphorus (P) along 130 km of the Calapooia River (Oregon, USA) and 44 of its sub-basins for three years to test for associations with land use. Nutrient concentrations were analyzed for spatial and seasonal patterns and for relationships with land-use and stream discharge. Ortho-P and DN were higher in lower-elevation sub-basins dominated by poorly-drained soils and agricultural production compared to higher-elevation sub-basins dominated by well-drained soils and forests. Eight lower basins had at least one sample period with nitrate-N >10 mg L-1. The Calapooia River had lower dissolved nutrient concentrations compared to lower sub-basins, often by an order of magnitude. Dissolved organic N represented a greater proportion of DN in the upper forested sub-basins. Seasonal nutrient concentrations had strong positive correlations to the percent of a sub-basin that was managed for agriculture in all seasons (p-values≤0.019) except summner. Results suggest that agricultural lands are contributing to stream nutrient concentrations. However, poorly drained soils in agricultural areas may also contribute to the strong relationships that we found between dissolved nutrients and agriculture.

Purpose/Objective:

Extensive water samples were collected over a period of three years along the river network and tributary streams of the Calapooia River in western Oregon. Samples were analyzed for dissolved nitrogen (DN) and ortho-phosphorus (P). Ortho-P and DN were higher in lower-elevation sub-basins dominated by poorly-drained soils and agricultural production compared to higher-elevation sub-basins dominated by well-drained soils and forests. The Calapooia River had lower dissolved nutrient concentrations compared to lower sub-basins, often by an order of magnitude. Results suggest that agricultural lands are contributing to stream nutrient concentrations. However, poorly drained soils in agricultural areas may also contribute to the strong relationships that we found between dissolved nutrients and agriculture.

URLs/Downloads:

ABSTRACT - EVANS.PDF   (PDF,NA pp, 59.742 KB,  about PDF)

Record Details:

Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Start Date: 04/22/2014
Completion Date: 04/22/2014
Record Last Revised: 06/19/2015
Record Created: 04/22/2014
Record Released: 04/22/2014
OMB Category: Other
Record ID: 273851

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB

WESTERN ECOLOGY DIVISION

FRESHWATER ECOLOGY BRANCH