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Comparison of trends in stream water quality
Author(s) -
Potts J. M.,
Hirst D.,
Miller J. D.,
Edwards A. C.,
Elston D. A.
Publication year - 2003
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.1253
Subject(s) - streams , environmental science , hydrology (agriculture) , autocorrelation , water quality , smoothing , spline (mechanical) , streamflow , statistics , geology , drainage basin , geography , mathematics , computer science , ecology , cartography , geotechnical engineering , biology , computer network , structural engineering , engineering
Abstract 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.