Upscaling Preferential Flow in Heterogeneous Porous Media from the Laboratory to the Field

ue to public health or environmental concerns, performing tracer tests in the field by injecting pathogenic microorganisms or contaminants of emerging concern into groundwater is not permitted. Therefore, examining the effects of preferential flow processes on these contaminants under controlled saturated conditions must be done in the laboratory, but the resulting transport parameters cannot be directly applied to field-scale groundwater models. This research considers how an upscaling relationship can be found using a colloidal tracer and three different scales: small laboratory columns (0.1 m scale), a large intact core (1 m scale), and a real-world gravel aquifer (10 m scale). The small columns were filled with gravel from boreholes at the field site, an alluvial gravel aquifer close to Vienna, Austria. The mesoscale consists of an undisturbed gravel column from a gravel pit near Neuhofen an der Ybbs, Austria. Results showed that a certain pattern emerges after an initial scale-dependent threshold, regardless of differences due to the small columns being repacked with aquifer material and the large column and field site being “undisturbed”. In this way, the mesoscale column allows us to gain insight into upscaling processes by incorporating an in-between step when comparing groundwater transport at the column- to the field scale.