Water vapor transport paths into the American Southwest were deduced from a high temporal resolution record of hydrogen isotope compositions of atmospheric water vapor (δDwv) collected over a six-week period in late spring, 2005, at Albuquerque, New Mexico. Daily fluctuations of δDwv routinely exceeded 20‰ in magnitude, while δDwv variations up to 80‰ occurred on the time scale of weather (a few hours to ∼ a week). Vertical profiles of δDwv in the lower troposphere exhibited considerable structure that cannot be ascertained from standard meteorological measurements. Trajectory analyses provide consistent evidence that the large temporal variations of surface δDwv and vertical variations of δDwv are primarily due to advection of water from different source regions. The lack of mixing inferred from our analyses indicates that δDwv can be used as a sensitive tracer of the moisture transport history of air parcels.