Hydrologic Studies in Oregon Nutrients, Aquatic Plant Growth, and pH and Dissolved Oxygen Levels in the Lower Yakima River, Washington Project Chief:
Cooperators: South Yakima and Benton Conservation Districts
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BACKGROUND During the past several years, aquatic plant growth has increased along much of the lower Yakima River (click opens PDF map, 0.8 MB). Such growth can lead to large diel (24-hour) swings in pH and dissolved oxygen concentrations. Excessively low dissolved oxygen concentrations and excessively low or high pH levels can reduce the diversity of animal life in a stream by stressing the physiological systems of most organisms and reducing reproduction. Monitoring data from the Washington Department of Ecology suggest that exceedences of the State water-quality standards for dissolved oxygen and pH are becoming more frequent. The goal of this study is to gain an understanding of the complex interactions between nutrient concentrations and loadings, stream characteristics, climatic conditions, stream biology, and water quality in the Yakima River to help natural-resource managers make informed decisions regarding land use in the basin. |  |
OBJECTIVES
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Quantify diel variations in water-quality indicators (dissolved oxygen, pH, temperature, turbidity, and chlorophyll) and seasonal changes in stream chemistry, turbidity, and aquatic plant growth in the lower Yakima River
Characterize distinct reaches in the lower Yakima River with regard to morphology, aquatic plant growth, pH, and dissolved oxygen concentrations, and determine if these reaches are meeting the Washington State water quality standards for pH and dissolved oxygen
Assess the relations among physical parameters, aquatic plant characteristics, diel DO and pH levels, and nutrient concentrations, and how these relations differ among the different river reaches during the irrigation season
Measure the levels of turbidity and the instantaneous loads of nutrients and suspended sediment in the lower Yakima River and its major tributaries, perform a mass balance on instantaneous suspended sediment and nutrient loads in the lower Yakima River, identify sites and reaches of major nutrient inflow from surface or ground water and major sources and sinks
Determine whether there have been recent changes in water quality in the lower Yakima River compared with historical conditions
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APPROACH In the first year of the study we will determine the location of morphologically distinct reaches in the river that will be used in subsequent stages of the study as well as assess the lower Yakima River and important tributaries in order to determine:
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At the end of the first year, hypotheses will be formulated to explain the geographic variations (among reaches) and temporal variations (within days and between seasons) in water chemistry and aquatic plant growth. In the second through fourth years of the study, the hypotheses formulated after the first year will be tested by performing more detailed and targeted assessments of water chemistry and aquatic plant growth in selected reaches of interest. The goal will be to improve on the quantification of the reach characteristics and on our understanding of the processes associated with the most important hypotheses.
Yakima River Basin Studies Page
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URL: http://or.water.usgs.gov/projs_dir/yakima_nutrients/index.html
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Last modified Wednesday - Apr 21, 2004 at 19:22:31 EDT
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