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Scientific Investigations Report 2013–5199

Prepared in cooperation with Washington State Department of Ecology and U.S. Environmental Protection Agency

Estimation of Total Nitrogen and Total Phosphorus in Streams of the Middle Columbia River Basin (Oregon, Washington, and Idaho) Using SPARROW Models, with Emphasis on the Yakima River Basin, Washington

By Henry M. Johnson, Robert W. Black, and Daniel R. Wise

Abstract

The watershed model SPARROW (Spatially Related Regressions on Watershed attributes) was used to predict total nitrogen (TN) and total phosphorus (TP) loads and yields for the Middle Columbia River Basin in Idaho, Oregon, and Washington. The new models build on recently published models for the entire Pacific Northwest, and provide revised load predictions for the arid interior of the region by restricting the modeling domain and recalibrating the models. Results from the new TN and TP models are provided for the entire region, and discussed with special emphasis on the Yakima River Basin, Washington.

In most catchments of the Yakima River Basin, the TN and TP in streams is from natural sources, specifically nitrogen fixation in forests (TN) and weathering and erosion of geologic materials (TP). The natural nutrient sources are overshadowed by anthropogenic sources of TN and TP in highly agricultural and urbanized catchments; downstream of the city of Yakima, most of the load in the Yakima River is derived from anthropogenic sources. Yields of TN and TP from catchments with nearly uniform land use were compared with other yield values and export coefficients published in the scientific literature, and generally were in agreement. The median yield of TN was greatest in catchments dominated by agricultural land and smallest in catchments dominated by grass and scrub land. The median yield of TP was greatest in catchments dominated by forest land, but the largest yields (90th percentile) of TP were from agricultural catchments. As with TN, the smallest TP yields were from catchments dominated by grass and scrub land.

Posted November 25, 2013

For additional information, contact:
Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201
http://or.water.usgs.gov/

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Suggested citation:

Johnson, H.M., Black, R.W., and Wise, D.R., 2013, Estimation of total nitrogen and total phosphorus in streams of the Middle Columbia River Basin (Oregon, Washington, and Idaho) using SPARROW models, with emphasis on the Yakima River Basin, Washington: U. S. Geological Survey Scientific Investigations Report 2013–5199, 28 p., http://dx.doi.org/10.3133/sir20135199.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Methods

Evaluation of Calibrated Models

Modeling Results for the Yakima River Basin

Model Calibration and Uncertainty

Nutrient Yields and Land Use

Comparison with Regional SPARROW Model

Summary

References Cited

Appendix A. Prediction Results and Calibration Loads

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