Preliminary studies of water seepage through rough-walled fractures

For groundwater aquifers in fractured rock, fractures play a significant role in the transport of water and contaminants through the unsaturated zone to the groundwater table. Fractures can provide preferential flow paths for infiltrating liquids that dramatically accelerate contaminant transport compared to predictions based upon spatially uniform infiltration. The actual liquid distribution during infiltration determines the contact area between the flowing water and rock, and liquid residence time, which in turn affects the potential for rock-water and rock-solute interaction, as well as mass transfer between liquid and gas phases. This report summarizes flow- visualization experiments of water percolation through transparent replicas of a natural rock fracture. We have focused on phenomenological and exploratory experiments that can lead to a conceptual model which incorporates the important physical mechanisms that control flow