Smoothing analysis of slug tests data for aquifer characterization at laboratory scale

•Analysis of hydraulic heads from slug tests by a 3D laboratory model.•SG filter, FT and two WTs were used to smooth out the noise in the hydraulic heads.•The Mexican hat wavelet and a measurement frequency of 100 Hz gave optimal results.•Energy contents and frequency oscillations were exploited by...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 2018-07, Vol.562, p.125-139
Main Authors: Aristodemo, Francesco, Ianchello, Mario, Fallico, Carmine
Format: Article
Language:English
Subjects:
Hydraulic conductivity
Hydraulic head
Slug tests
Smoothing
Wavelet analysis
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Summary:•Analysis of hydraulic heads from slug tests by a 3D laboratory model.•SG filter, FT and two WTs were used to smooth out the noise in the hydraulic heads.•The Mexican hat wavelet and a measurement frequency of 100 Hz gave optimal results.•Energy contents and frequency oscillations were exploited by the Wavelet Transform. The present paper proposes a smoothing analysis of hydraulic head data sets obtained by means of different slug tests introduced in a confined aquifer. Laboratory experiments were performed through a 3D large-scale physical model built at the University of Calabria. The hydraulic head data were obtained by a pressure transducer placed in the injection well and subjected to a processing operation to smooth out the high-frequency noise occurring in the recorded signals. The adopted smoothing techniques working in time, frequency and time-frequency domain are the Savitzky-Golay filter modeled by third-order polynomial, the Fourier Transform and two types of Wavelet Transform (Mexican hat and Morlet). The performances of the filtered time series of the hydraulic heads for different slug volumes and measurement frequencies were statistically analyzed in terms of optimal fitting of the classical Cooper’s equation. For practical purposes, the hydraulic heads smoothed by the involved techniques were used to determine the hydraulic conductivity of the aquifer. The energy contents and the frequency oscillations of the hydraulic head variations in the aquifer were exploited in the time-frequency domain by means of Wavelet Transform as well as the non-linear features of the observed hydraulic head oscillations around the theoretical Cooper’s equation.
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2018.04.056