Geostatistical Techniques to Obtain the 3-D Hydraulic Conductivity Distribution Model in the Southern Po River Plain

The main objective of this research is to assess the hydraulic conductivity (k) distribution in the Southern Po River plain (Emilia Romagna region), where fine silty and silty-sandy deposits are interdigitated with coarser sandy and sandygravelly sediments. The k distribution is the main issue to be faced in hydrogeological numerical modeling. Usually, this parameter is assigned to each hydrogeological complex, considering values coming from point permeability tests (e.g. pumping tests, slug tests, etc.). Although the calibration methods allow a good model optimization, the natural variability of the hydraulic properties cannot be reproduced in detail using deterministic and point approaches to calibration. For this reason, a 3-D geostatistical method was applied to draw estimations of the hydraulic conductivity of a continuous 3-D model of the subsoil. A mechanical model was built through 182 Cone Penetration Test (CPT) profiles of tip qc and shaft fs resistances, collected by the Emilia Romagna Regional Geological Survey. In particular, the Ordinary Kriging technique was applied to the qc and fs variables which allow to obtain the Ic index 3-D model and the relative k 3-D model, by means of the equations available in literature. The geostatistical results show a clear variation of the hydraulic conductivity among the different deposits identified in the study area. Moreover, the proposed method provided a good reliability of k estimated values, which could be used as a good starting point for hydrogeological modeling and as constraints for model calibration.