Impacts of the Scale of Representation of Heterogeneity on Simulated Salinity and Saltwater Circulation in Coastal Aquifers

Abstract Numerical models of variable‐density groundwater flow and salt transport are a primary tool for predicting salinity distributions in coastal aquifers estimating submarine discharge (SGD). Models particularly useful to estimate the saline component SGD, which can occur far offshore is difficult measure directly. Depending on system application, level geologic detail represented range from homogeneous or layered fully heterogeneous hydraulic conductivity fields. These features strongly affect model results, limiting understanding subsurface associated density‐driven saltwater circulation along coasts worldwide. In this study, impact scale representation heterogeneity SGD was investigated using numerical simulations. Upscaling significantly modify paths, resulting unpredictable variations simulated though values fields with equivalent show consistent trends. Simulated density control both rate direction circulation. The length mixing zone perimeter, distribution complexity, shown correlate amount circulating reverse cases. Overall, results demonstrate strong dependence models. This suggests that simplified structure may substantially underestimate circulation, attempts calibrate them measurements be problematic.