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Methodology for river-quality assessment with application to the Willamette River basin, Oregon

Circular 715-M

By:
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Abstract

For nearly half a century the Willamette River in Oregon experienced severe dissolved-oxygen problems related to large loads of organically rich waste waters from industries and municipalities. Since the mid-1950 's dissolved oxygen quality has gradually improved owing to low-flow augmentation, the achievement of basinwide secondary treatment, and the use of other waste-management practices. As a result, summer dissolved-oxygen levels have increased, salmon runs have returned, and the overall effort is widely regarded as a singular water-quality success. To document the improved dissolved-oxygen regimen, the U.S. Geological Survey conducted intensive studies of the Willamette during the summer low-flow seasons of 1973 and 1974. During each summer the mean daily dissolved-oxygen levels were found to be higher than 5 milligrams per liter throughout the river. Because of the basinwide secondary treatment, carbonaceous deoxygenation rates were low. In addition, almost half of the biochemical oxygen demand entering the Willamette was from diffuse (nonpoint) sources rather than outfalls. These results indicated that point-source biochemical oxygen demand was no longer the primary cause of dissolved-oxygen depletion. Instead, the major causes of deoxygenation were nitrification in a shallow ' surface active ' reach below Salem and an anomalous oxygen demand (believed to be primarily of benthal origin) in Portland Harbor. (Woodard-USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Methodology for river-quality assessment with application to the Willamette River basin, Oregon
Series title:
Circular
Series number:
715
Chapter:
M
Edition:
-
Year Published:
1976
Language:
ENGLISH
Publisher:
U.S. Govt. Print. Off.,
Description:
vii, p M1-M55, ill., maps ;28 cm.