SAMPLING AND ANALYTICAL TOLERANCE REQUIREMENTS FOR DETECTING TRENDS IN WATER QUALITY1

Authors

  • Graham B. McBride,

    1. Scientists, NIWA National Institute of Water and Atmospheric Research Ltd.), P.O. Box 11–115, Hamilton, New Zealand. (Dr. Smith's present address: New York City Department of Environmental Protection, 465 Columbus Avenue, Valhalla, New York 10595.)
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  • David G. Smith

    1. Scientists, NIWA National Institute of Water and Atmospheric Research Ltd.), P.O. Box 11–115, Hamilton, New Zealand. (Dr. Smith's present address: New York City Department of Environmental Protection, 465 Columbus Avenue, Valhalla, New York 10595.)
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  • 1

    Paper No. 96022 of the Journal of the American Water Resources Association (formerly Water Resources Bulletin). Discussions are open until October 1, 1997.

Abstract

ABSTRACT: In designing a water quality sampling program, the detection threshold (equivalent to “effect size” in a power analysis) can be calculated as a function of the Type I and II error risks, sampling frequency and duration, and (if appropriate) autocorrelation. Then the impact of sampling and analytical errors on the trend that can be detected within that threshold should be considered. A procedure for doing so is described, enabling a priori prescription to laboratory and field staff of the analytical tolerances expected of them in their work. It assumes that the trend (a linear or step change) can be described by a parametric model.

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