• groundwater transport;
  • predictive modeling;
  • accuracy;
  • field-scale tracer experiments;
  • macrodispersion;
  • diffusive mass transfer;
  • travel time

[1] We study predictive modeling of groundwater transport that accounts for three mechanisms: mean advection, macrodispersion, and mass transfer. A general methodology is presented and applied to a series of nonsorbing tracer tests along multiple pathways on scales ranging from ca. 70 to 300 m, in a highly heterogeneous aquifer at Forsmark (Sweden). The mean water residence time cannot be predicted well using a simple water balance model. Longitudinal macrodispersivity λL (L) and a mass transfer parameter group inline image are extrapolated from the control tracer experiments, to yield accurate predictions of tracer discharge, once the mean water residence time is constrained. A relatively simple modeling framework based on Fickian macrodispersion and diffusion seems to be adequate for reproducing the tracer discharge in this complex and highly heterogeneous porous media.