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United States Department of Agriculture

Agricultural Research Service

Title: Relationships Between Dissolved Nitrogen and Landuse/landcover at Two Spatial Scales in the Calapooia River Watershed, Oregon

Authors
item Floyd, William - OREGON STATE UNIVERSITY
item Schoenholtz, S - OREGON STATE UNIVERSITY
item Griffith, Stephen
item Wigington, P - US EPA
item Steiner, Jeffrey

Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: February 28, 2004
Publication Date: June 28, 2004
Citation: Floyd, W.S., Schoenholtz, S., Griffith, S.M., Wigington, P., Steiner, J.J. 2004. Relationships between dissolved nitrogen and landuse/landcover at two spatial scales in the Calapooia River watershed, Oregon. In:Proceedings of the American Water Resources Association Summer Specialty Conference, June 28-30, 2004, Middleburg, Virginia. 2004 CD-ROM.

Interpretive Summary: The Calapooia River, a major tributary to the Willamette River in Oregon, provides an outstanding opportunity to study dynamics of dissolved nitrogen (DN) in a multiple landuse watershed. The watershed is typical of many found in the Willamette basin, with National Forest land in the headwaters, industrial forestry practices in its upper reaches, forestry and mixed agriculture in the middle portion, a lower section that is almost entirely grass seed farming, and small urban centers found throughout. The Oregon Department of Environmental Quality has designated water quality in the Calapooia River as poor, identifying nitrate-nitrogen and ammonium-nitrogen levels as high. To gain a better understanding of the relationship between landuse/landcover (LULC) and DN dynamics within the watershed, 90 sites were selected for synoptic water quality sampling of surface water at monthly intervals. Forty-four of the sites are at the mouth of small sub-basins between 3.0 and 20 km2 and provide the basis for statistical comparison. Synoptic sampling began in October 2003 and will continue. Preliminary results indicate a relationship between landuse and DN levels, particularly nitrate during the early winter when rainfall is high. Relationships between LULC and DN in the 44 small sub-basins are being explored at two spatial scales: (i) the sub-basin level and (ii) within 150 m of the stream network. Analysis at these scales will provide an indication of how LULC within sub-basins and in proximity to stream networks influences DN concentrations.

Technical Abstract: The Calapooia River, a major tributary to the Willamette River in Oregon, provides an outstanding opportunity to study dynamics of dissolved nitrogen (DN) in a multiple landuse watershed. The watershed is typical of many found in the Willamette basin, with National Forest land in the headwaters, industrial forestry practices in its upper reaches, forestry and mixed agriculture in the middle portion, a lower section that is almost entirely grass seed farming, and small urban centers found throughout. The Oregon Department of Environmental Quality has designated water quality in the Calapooia River as poor, identifying nitrate-nitrogen and ammonium-nitrogen levels as high. To gain a better understanding of the relationship between landuse/landcover (LULC) and DN dynamics within the watershed, 90 sites were selected for synoptic water quality sampling of surface water at monthly intervals. Forty-four of the sites are at the mouth of small sub-basins between 3.0 and 20 km2 and provide the basis for statistical comparison. Synoptic sampling began in October 2003 and will continue. Preliminary results indicate a relationship between landuse and DN levels, particularly nitrate during the early winter when rainfall is high. Relationships between LULC and DN in the 44 small sub-basins are being explored at two spatial scales: (i) the sub-basin level and (ii) within 150 m of the stream network. Analysis at these scales will provide an indication of how LULC within sub-basins and in proximity to stream networks influences DN concentrations.

Last Modified: 8/21/2014
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