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    Volume 40, Issue 1 (January 2017)

    Taking into Account Data Accuracy for Interpretation of Slug Tests in Confined or Unconfined Aquifers

    (Received 14 September 2015; accepted 11 October 2016)

    Published Online: 2017

    CODEN: GTJODJ

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    Abstract

    Different methods may be used to interpret the data of slug tests performed in aquifers, which are the water column height, Z, and time, t. The data accuracy usually is not taken into account. However, all measured Z data contain a random error and may contain a systematic error. This paper is believed to be the first one to explain how to assess the random error and display it in plots and, then, how to extract the systematic error, using three diagnostic graphs (two semi-log plots and a derivative plot that unifies all theories, and yields user-independent results). The plot of logZ versus t with “error” bars has a distinctive look: all Z data have the same “error,” but the smallest logZ data are the most inaccurate. As a result, the error bar is small at early times (large Z), but it increases to become very large at late times (small Z), which may modify the interpretation of data. Finally, the paper quantifies the errors that are made when using the Hvorslev equation for curved plots without error bars. Most often, the curvature results from a systematic error on the assumed piezometric level. When this error is not acknowledged, the user is at liberty to interpret the data and extract a hydraulic conductivity, K, which fits some beliefs. This yields a large error on K, which is quantified using equations and graphs.


    Author Information:

    Chapuis, R. P.
    Dept. of Civil, Geological and Mining Engineering, École Polytechnique, Montreal, Quebec

    Duhaime, F.
    Laboratory for Geotechnical and Geoenvironmental Engineering (LG2), École de Technologie Supérieure, Montreal, Quebec


    Stock #: GTJ20150211

    ISSN:0149-6115

    DOI: 10.1520/GTJ20150211

    Author
    Title Taking into Account Data Accuracy for Interpretation of Slug Tests in Confined or Unconfined Aquifers
    Symposium ,
    Committee D18