The vadose zone provides an important link between the Earth’s surface and groundwater, and influences a wide range of critically important environmental hydrologic phenomena such as recharge, ET, and transport of species (e.g., emergent contaminants). However, the spatial and temporal dynamics of many vadose zone processes and hydrologic controls of species transport are still poorly understood due to the random and structural heterogeneities that exist across scales in both time and space, the complexities and non-linearities that occur within and between processes, and the difficulties associated with monitoring and quantifying these heterogeneities and their impact on hydrologic and biogeochemical processes. We solicit abstracts that address the above-mentioned challenges. Topics of interest include, but are not limited to—unsaturated and multiphase flow and transport, preferential flow, novel parameterization approaches, climate change-induced processes and new hydrologic regimes, and measurement techniques that combine geophysical approaches with hydrological modeling—as applicable to the vadose zone.