Estimation of hydraulic conductivity using the slug test method in a shallow aquifer in the venetian plain (NE, Italy)

The slug test offers a fast and inexpensive field method of obtaining localized hydraulic conductivity values. In this paper, we applied this procedure in a ‘fontanili’ zone located in the middle Venetian Plain (Villaverla, VI). In this site, 34 piezometers are present in a small area of 1.5 ha, which intercepts a shallow unconfined aquifer. The experimental data, obtained by 59 slug tests, were processed with three different methods of analysis: Hvorslev, Bouwer-Rice and KGS, to obtain a permeability characterization of the area and identify the real differences between the considered solutions. Two slug tests were also analyzed using a three-dimensional finite difference groundwater flow model. By comparing the different methods used in the same piezometer, we obtained highly similar values of permeability, while the numerical simulation of slug tests suggests that KGS is the best method for estimating hydraulic conductivity. At the same time, we can identify a considerable heterogeneity in the area of investigation; indeed, the slug test estimates of hydraulic conductivity (K) range over three orders of magnitude (from 2.6E- 06 to 3.8E-03 m/s). This wide range of values confirms the high stratigraphic heterogeneity also observed during the coring.