Technical Abstract: Considerable progress has been made in recent years in the modeling of individual hydrological processes such as infiltration, surface runoff, evaporation and solute transport. However, a fuller appreciation of the workings of the natural environment requires understanding of the interactions between various processes at a variety of spatial and temporal lscales. This special issue of Hydrological Processes contains a combinatio of modelling and field measurement approaches aimed at gaining insights into process interactions and space-time dynamics related to flow and transport in watersheds, rivers and estuaries. Such insights may have profound impli-cations for environmental management.