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LONGITUDINAL AND LATERAL PATTERNS IN PHYSICAL AND CHEMICAL ATTRIBUTES OF WILLAMETTE RIVERINE HABITAT
Citation:
Landers, D H., M. MorrisonErway, A. G. Fernald, S P. Cline, AND C. Andrus. LONGITUDINAL AND LATERAL PATTERNS IN PHYSICAL AND CHEMICAL ATTRIBUTES OF WILLAMETTE RIVERINE HABITAT. Presented at Willamette River Basin Water Quality Data Summit, Corvallis, Oregon, May 25, 2000.
Description:
The Willamette River in western Oregon is the tenth largest river in the conterminous U. S. Plans are being developed to restore ecological function to the main corridor of the river. Our riverine research has developed a basic understanding of some of the ecological functions and process important to riparian, off-channel habitats (OCH) that are connected to the main channel at summer base flow. These features are highly diverse morphologically, functionally and developmentally. Bar complexes associated with these types of OCHs provide a broad template for riparian vegetation development. OCH are of great importance to many native fish species for rearing, refugia and feeding. They are also important loci with respect to hyporheic flow and the associated physical and chemical changes in water quality. All of these ecological functions vary greatly spatially and temporally according to the hydrograph and season.
We have sampled many physical and chemical water chemistry parameters of the main channel (Eugene to Willamette Falls), non-flowing off-channel habitats (Eugene to Corvallis), and ground water (Eugene to Corvallis). Results indicate that at summer low flow there is considerable diversity in these parameters: longitudinally, laterally and vertically within the active floodplain of the river. Dissolved nitrate increases about four fold between Eugene and Willamette Falls in both winter and summer (winter being higher) and appears to be associated with non point source discharges. pH tends to decrease downstream but remains circumneutral. Specific conductance is a good indicator of both groundwater (i.e. hyporheic flow) and industrial/municipal discharges and tends to double as the water mass moves downstream. Pulp mill discharges appear to influence main channel specific conductance greatly. Dissolved organic carbon also increases (~25%) in the downstream direction and appears to be almost totally dominated by pulp mill discharges. Winter and summer values differ greatly as the quantity of flow increases, diluting point and non-point discharges. Winter turbidity increases about 3 fold downstream and appears to be dominated by non point sources. Many off-channel habitats differ considerably from the main channel, offering refugia and important high quality rearing habitats for native fish.