Inversion of hydraulic conductivity from Induced Polarisation, Part B: field examples from five countries

Summary The knowledge about the hydraulic conductivity of the subsurface is crucial to know as it is a main parameter for groundwater flow characterization within an aquifer. The geophysical method time-domain Induced Polarisation has been shown to be useful for estimating the hydraulic conductivity. By using a new inversion approach, where we directly invert for hydraulic properties as inversion parameters, the estimation of the hydraulic conductivity can be improved. We have measured at several test sites across five European countries, all characterized by unconsolidated sediments, but with differences in terms of the water electrical conductivity. In particular, at the Zeeland site in the Netherlands, a strong gradient in the water electrical conductivity is present since a freshwater lens is overlaying the sea water. A very good agreement between the hydraulic conductivity values from the inversion with the present hydraulic model can be observed, despite of the high water electrical conductivity, which makes it challenging to identify the clay layers at the site. Similar results were achieved for the other tests sites. Therewith, this new methodology might open the way for reliable, cost-effective geophysical estimation of hydraulic conductivity in the field.