TECHNICAL NOTES
Jul 1, 1996
Graphical Methods for Assessing Changes in Water Quality
Publication: Journal of Environmental Engineering
Volume 122, Issue 7
Abstract
The purpose of this paper is to demonstrate seasonal subseries and multipercentile graphs for analyzing trends in environmental data time series (Tukey 1977; Cleveland 1985). These simple graphical methods do not require the user to make assumptions regarding properties of the data, such as normality, constant variance, and serial independence. A modest number of missing values (up to 30, assuming they occur at random intervals) should not affect the plots enough to alter the interpretation. The plots allow one to see more clearly what is happening at the extremes, and seasonal effects are revealed. The methods are illustrated by using five day BOD data, measured at monthly intervals from 1977 to 1992 at the DePere station on the Fox River in Wisconsin.
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References
1.
Cleveland, W. S. (1985). The elements of graphing data . Wadsworth Advanced Books and Software, Monterey, Calif.
2.
Tukey, J. W. (1977). Exploratory data analysis . Addison-Wesley Publishing Co., Reading, Mass.
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Copyright © 1996 American Society of Civil Engineers.
History
Published online: Jul 1, 1996
Published in print: Jul 1996
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Authors
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Karen Cozzetto
Proj. Asst., Wisconsin Dept. of Natural Resour., Madison, WI 53706.
P. M. Berthouex, Associate Member, ASCE
Prof., Civ. and Envir. Engrg., Univ. of Wisconsin-Madison, Madi- son, WI.
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ASCE Library Cards let you download journal articles, proceedings papers, and available book chapters across the entire ASCE Library platform. ASCE Library Cards remain active for 24 months or until all downloads are used. Note: This content will be debited as one download at time of checkout.
Terms of Use: ASCE Library Cards are for individual, personal use only. Reselling, republishing, or forwarding the materials to libraries or reading rooms is prohibited.
Terms of Use: ASCE Library Cards are for individual, personal use only. Reselling, republishing, or forwarding the materials to libraries or reading rooms is prohibited.