“…Regional groundwater quality management models must upscale the transport equation sufficiently to represent the effects of heterogeneity, including preferential flow in well‐connected high‐conductivity networks and mass transfer between the high‐ and low‐conductivity media. The early arrivals of contaminants caused by the preferential flow and the asymptotical tails resulting from transport through low permeability materials have been frequently observed, which significantly challenges long‐term management (e.g., Bianchi et al, ; Brusseau & Guo, ; Brusseau et al, , ; Dearden et al, ; Fogg et al, ; Fogg & LaBolle, ; Fogg & Zhang, ; Guo & Brusseau, ; LaBolle & Fogg, ; Matthieu et al, ; Seyedabbasi et al, ). Although the effects of heterogeneity can be simulated by explicitly including the spatial variability of hydraulic properties in the model, this approach is not feasible for most plume‐scale contamination sites and is definitely not feasible for regional‐scale models covering 10s to 100s of kilometer.…”