The Hydrologic Sciences Program is a disciplinary program within the Division of Earth Sciences. Hydrologic science has a distinct focus on continental water processes at all scales, and the program supports research with a primary focus on these processes. The program supports fundamental research about water on and beneath the Earths surface, as well as relationships of water with material and living components of the environment. A major focus is the study of hydrologic processes (e.g., rainfall and runoff; infiltration and subsurface flow; evaporation and transpiration), as well as fluxes of water (e.g. in soils, aquifers, and streams). Many projects involve the study of hydrologic transport (e.g., of dissolved solutes, sediment), coupling of hydrological processes with other systems (e.g., ecosystem processes, geochemical cycles, food and energy systems, socio-ecological systems), or hydrologic responses to change (e.g., changes in land use, climate, or watershed management). Observational, experimental, theoretical, and modeling approaches are supported.