Fluid Stretching at Facies Interfaces Governs Solute Transport

Abstract This study provides a kinematic explanation for why facies interfaces dominate solute transport in heterogeneous aquifers. Using flow and transport simulations, we apply kinematic metrics to quantify deformation processes that control plume evolution. Results show that strong conductivity contrasts generate preferential flow corridors, while transitional zones at facies interfaces act as persistent mixing fronts where stretching and folding intensify mixing. These cross‐facies transitions emerge as the primary controls on transport observables such as dispersion and dilution, with within‐facies variability exerting secondary effects. By linking sedimentary architecture to flow deformation, this work provides the mechanistic justification for earlier findings that cross‐transition probabilities govern solute spreading. The results highlight the need to resolve geologic interfaces in both field characterization and remediation design. Flow topology offers a unifying framework for predicting transport in aquifers and points to opportunities for geophysical methods to target the key architectural features that regulate mixing and dilution.