Significant uncertainty continues to be associated with the global water cycle and its potential variations from sub-seasonal to century time scales. Projections of water transport in coupled land-atmosphere-ocean numerical models of the climate system are typically one of the most uncertain elements, and may in turn be a limiting factor in our ability to predict other aspects of the climate system. This presentation highlights some facets of the multiscale aspects of the system dynamics that need to be better understood, and proposes an Eulerian-Lagrangian framework under which a hierarchical analysis of the water cycle could be developed. Prospects for improvement in specific aspects of the terrestrial and atmospheric branches of the water cycle and their implication for hydrologic applications considering both human modifications of the system and natural variability are discussed.