The Earth’s critical zone (CZ) is defined as the upper layer of the Earth’s surface—from bedrock to the tree canopy—and is dependent upon the co-evolution of Earth system processes including interactions among climate, hydrology, biogeochemistry, and geology. Water is the lifeblood driving CZ functions that underlie the expression of landscapes we see and a crucial resource on which all organisms rely. Despite the fundamental importance of water in CZ processes, there is not widespread understanding of the relation between how, when, and where water is stored in the CZ and how it affects key CZ processes, or how global change drivers (e.g., climate shifts and disturbance) will modify these interactions. Ecohydrological research over the last two decades has demonstrated that subsurface structure and topographic complexity strongly influence plant-available water, groundwater recharge, and streamflow generation, with the CZ community calling for research focused on the importance of spatially and temporally dynamic water stores (e.g., Brooks et al., 2015; Fan, 2015).