Comparison of trends in stream water quality

A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying tr...

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Bibliographic Details
Published in:Hydrological processes 2003-08, Vol.17 (12), p.2449-2462
Main Authors: Potts, J. M., Hirst, D., Miller, J. D., Edwards, A. C., Elston, D. A.
Format: Article
Language:English
Subjects:
British Isles, Scotland
Earth sciences
Earth, ocean, space
Exact sciences and technology
Hydrology
Hydrology. Hydrogeology
nitrate
rivers
seasonality
spline
trends
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Summary:A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying trend. The method involves fitting the model twice, once with the underlying trends constrained to be identical for each river and once with the trends unconstrained. Statistical properties are assessed by simulation methods that allow for the autocorrelation in the residuals from the unconstrained fit. The method is applied to data from two streams in the Balquhidder catchments in the Highlands of Scotland and to data from the Dee, Don and Ythan rivers in the north‐east of Scotland. Copyright © 2003 John Wiley & Sons, Ltd.
ISSN:0885-6087
1099-1085
DOI:10.1002/hyp.1253