Measurements of Interactions between Resident and Infiltrating Water in a Lattice Micromodel

The interplay between resident water (“old water”) and infiltrating water (“new water”) in porous media was examined through experiments in an idealized, two‐dimensional, glass micromodel. Image analysis was used to quantify the miscible interplay between old and new water during a cycle of imbibition by new water and drainage by air in a domain that was partially saturated with old water. The dynamics of the old–new water exchange were characterized in terms of several parameters: remaining old water, number of old‐water pockets, volumetric fraction, and degree of mixing. In particular, it was found that some old water remained in the system at long times within stable water pockets; these pockets may remain stable even after a second cycle of infiltration.