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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #260868
Title: Impact of land use patterns and agricultural practices on water quality in the Calapooia River Basin of western Oregon

Author
item Mueller Warrant, George
item Griffith, Stephen
item Whittaker, Gerald
item Banowetz, Gary
item Pfender, William
item GARCIA, TIFFANY - Oregon State University
item GIANNICO, GUILLERMO - Oregon State University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2012
Publication Date: 5/31/2012
Citation: Mueller Warrant, G.W., Griffith, S.M., Whittaker, G.W., Banowetz, G.M., Pfender, W.F., Garcia, T.S., Giannico, G.R. 2012. Impact of land use patterns and agricultural practices on water quality in the Calapooia River Basin of western Oregon. Journal of Soil and Water Conservation. 67(3):183-201.

Interpretive Summary: Our objectives were to identify and quantify the sources of nitrogen and sediment present in streams of the Calapooia River basin in western Oregon. We collected samples for water quality measurements from streams draining 40 sub-basins on a monthly basis from October 2003 to January 2007. The sub-basins possessed wide ranges in permanent tree cover, agricultural landuse patterns, slopes, and soil types. Relationships among variables were tested using a variety of statistical tools, including some specifically defined to analyze spatial data. Sub-basins varied from 96% forest to 99% agriculture, from 1.3 to 18.9% slope, from 0.5 to 43.0 ppm total nitrogen maximums, and from 29 to 249 ppm suspended sediment maximums. Total nitrogen increased as percentage of seven common agricultural crops increased, and decreased as percentage of trees and one crop, Italian ryegrass, increased. Sediment concentrations were most strongly influenced by rainfall totals during periods of 4 and 14 days prior to sampling. A somewhat weaker effect of soil disturbance during planting was also seen. Transformations of total nitrogen over time identified four prominent groups of sub-basins: (1) those with low impact of nitrogen and a strong peak in December, (2) those with medium impact of nitrogen and the same timing pattern, (3) those with high impact of nitrogen and the same timing pattern, and (4) those with very high impact of nitrogen but no clear timing pattern.

Technical Abstract: The objectives of our study were to identify and characterize the sources of total nitrogen (N) and sediment differentially active within 40 sub-basins of the Calapooia River basin in western Oregon in monthly samples collected over three cropping years. The sub-basins included both independent and nested drainage types, with wide ranges in permanent tree cover, agricultural landuse patterns, slopes, and soil types. Associations among variables were tested using simple linear correlation, ordinary least squares regression, geographically weighted regression, and ANOVA. Sub-basins varied from 96% forest to 99% agriculture, from 1.3 to 18.9% average slope, from 0.5 to 43.0 ppm total N maximums, and from 29 to 249 ppm suspended sediment maximums. Total N was positively related to percent landcover of seven common agricultural crops and negatively related to cover by trees and one crop, Italian ryegrass. Sediment concentrations were most strongly related to rainfall totals during periods of 4 and 14 days prior to sampling, with weaker effects of agricultural practices that disturbed soil in conjunction with crop planting. Fourier transformations of total N over time identified four prominent groups of sub-basins: (1) those with low impact of N (up to 2 ppm) and a strong cyclical signal peaking in December, (2) those with medium impact of N (up to 8 ppm) and the same temporal pattern, (3) those with high impact of N (up to 21 ppm) and the same temporal pattern, and (4) those with very high impact of N (up to 43 ppm) and weak time series signal. When time series behavior of suspended sediment for the same four groups of sub-basins was examined, only the low and medium impact sites showed maximum peaks in the winter, and all four groups possessed much weaker temporal signals than occurred for total N.