Estimation of Unsaturated Flow Parameters by Inverse Modeling and GPR Tomography

The main goal of this work was to evaluate the possibility of estimating the flow parameters and geological structure of the unsaturated zone, also called vadose zone, using both geophysical and hydrological data and methods. The vadose zone at Moreppen field site located near Oslo’s Gardermoen airport was used as the case study. Moreppen field site has been the subject of numerous studies related to sedimentological, hydrological, geophysical and geochemical processes in the saturated and vadose zone. However, in the field of hydrology none of the previous studies at Moreppen used spatially continuous geophysical data to estimate the flow parameters at the field site. In this study, cross well GPR travel time tomography for the first time was used at Moreppen to map the spatial and temporal distribution of the electromagnetic (EM) wave velocity at the field site. The EM wave velocities were converted to the soil water content using a petrophysical relationship. Then using an inverse flow modeling conditioned on volumetric soil water content, we estimated hydrological parameters in the field site. Since snowmelt is the main groundwater recharge at Gardermoen, we focused our study to the water flow through the vadose zone during the snowmelt