The Hydrologic Sciences (HS) program funded by the National Science Foundation (NSF) supports basic research on the fluxes of water in the terrestrial environment that constitute the water cycle. The program is interested in understanding the physical, chemical, and/or biological processes coupled to water transport, including rainfall, runoff, infiltration, streamflow, evaporation, transpiration, and groundwater flow. The program supports observational, experimental, theoretical, modeling, synthesis, and field research approaches that may require joint review with related programs. Key evaluation criteria include the scientific merit, broader impacts, and the qualifications of the research team. Typical grant awards under the Geosciences program, which includes the Hydrologic Sciences program, range from $79,139 to $4,893,936 and span 1-5 year project periods. The research is predominantly performed at academic facilities, field sites, scientific observatories, and research vessels across the United States, with opportunities for interdisciplinary and international collaboration.