INVESTIGATION OF NON-FICKIAN DISPERSION USING LIDAR IMAGERY ON OUTCROPS

Dispersion in ground water systems typically demonstrates non-Fickian character that is largely believed to be due to variable velocity fields caused by aquifer heterogeneity; however, there is no clear link between parameters used to model the non-Fickian character and aquifer properties. In order to evaluate the influence of outcrop-scale heterogeneities (e.g., 2-5 meters), we interpret lithofacies from detailed outcrop scans using high-resolution terrestrial LiDAR, apply reasonable hydraulic conductivity values to these lithofacies, populate a 3-5 mm resolution grid with these conductivities, and model groundwater flow and solute transport through this grid. This produces a 2D model that captures realistic heterogeneity as observed in outcrop. We apply this approach to several outcrops in order to evaluate flow characteristics through different facies assemblages. The resulting groundwater simulations indicate that lithofacies variability produces a broad range of groundwater velocities, and particle tracking in these simulations produce a non-Fickian dispersion. However at time of writing an approach to classifying and quantifying this variable response is not clear. Additionally, the approach is currently limited to 2D simulations. Future research will focus on developing a means to predict non-Fickian dispersion parameters from more complex digital outcrop analogs.