Previous work in deep vadose zones of the arid southwest suggests that there is a shallow hydrologic system where plant roots are present and a deeper hydrologic system down to the water table. In the shallow system, I am interested to understand the role that pedogenic carbonate (i.e., caliche) plays in controlling water movement and transport. In the deeper vadose zone, I am curious to study the potential upward transport of volatile species as a result of differences in the temperature profile. Finally, I am interested to examine whether the shallow and deep hydrologic systems operate independently below playa environments (internal drainages) or whether playas serve as areas of groundwater recharge.