What causes spatial heterogeneity and homogeneity in runoff, evaporation, subsurface water and material fluxes (carbon and other nutrients, sediments), and in their sensitivity to their controls (e.g. snow fall regime, aridity, reaction coefficients)?
What are the hydrologic laws at the catchment scale and how do they change with scale?
Why is most flow preferential across multiple scales and how does such behaviour co-evolve with the critical zone?
Why do streams respond so quickly to precipitation inputs when storm flow is so old, and what is the transit time distribution of water in the terrestrial water cycle?