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EPISODIC EVENTS: THE EFFECT OF FLOODS ON NUTRIENT TRANSPORT IN A NORTHWESTERN, USA ESTUARY
Sigleo, A C. AND W. E. Frick. EPISODIC EVENTS: THE EFFECT OF FLOODS ON NUTRIENT TRANSPORT IN A NORTHWESTERN, USA ESTUARY. Presented at Pacific Estuarine Research Society Meeting, Portland, OR, May 2-4, 2002.
To estimate the effects of storms on nutrient transport, dissolved nutrients and suspended sediment loads were measured relative to stream discharge in the Yaquina River, OR for three storm events. Episodic events, particularly high rainfall or flood events may transport high dissolved nutrient loads along with large sediment loads. Water samples collected from 1998 through 2001were used to determine the annual suspended sediment and flow weighted silica and nitrate loads for the Yaquina River in Oregon. In the Yaquina River, dissolved silica concentrations increased from 120 ?M (pre-storm) to over 270 ?M in freshwater portions of the Yaquina River during the rising hydrograph and dropped to near zero at the storm height. Dissolved nitrate also increased rapidly (over 100 ?M) but decreased by 20 to 30 percent as the storm progressed. During the drought year 2001, total dissolved nitrate input was considerably less than in wetter years. Dissolved nitrate concentrations were unusually high ( up to186 ?M) in the first winter storm runoff after the drought. The results indicate that for the time interval studied, over 90% of the dissolved nitrate and silica were transported during the winter months of higher rainfall.
Record Details:Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
WESTERN ECOLOGY DIVISION
PACIFIC COASTAL ECOLOGY BRANCH