Reply to comment by E. Holzbecher on "Constant-concentration boundary condition: Lessons from the HYDROCOIN variable-density groundwater benchmark problem"

We appreciate the opportunity to continue a dialogue on solute-transport modeling issues and perhaps to clarify some of our original concerns. It appears to us that Holzbecher [this issue] fails to consider the physical implications of groundwater flow and solute transport along no-flow boundaries. A no-flow boundary coincides with a streamline along which the fluid velocity is generally nonzero. Because the velocity is nonzero, both advective and dispersive transport processes can be operative along a no-flow boundary.